ECOTOXICOLOGICAL BIOASSAYS OF THE EARTHWORMS ALLOLOBOPHORA CALIGINOSA SAVIGNY AND PHERETIMA HAWAYANA ROSA TREATED WITH ARSENATE

Little research has been carried out on the effect of arsenate on earthworms. Ecotoxicological laborat ory tests are fundamental tools for assessing the toxic i y of arsenate to soil organisms. In this study, t he impact of arsenate on the survival, reproduction and behav iour of the endogenic earthworms Allolobophora caliginosa and the anecic earthworms Pheretima hawayana has been quantified. The 96-h LC 50 of arsenate was estimated as 233.43 mg arsenate Kg −1 soil. d.w. for P. hawayana which is significantly higher than that of A. caliginosa 147.24±27.16 mg arsenate kg −1 soil d.w. The number of juveniles of P. hawayana was significantly higher than that of A. caliginosa at the arsenate concentrations 180, 240 and 400 mg kg soil dry weight. With the exception of the control (6.5 mg arsenate kg −1 soil.d.w.), P. hawayana showed an avoidance behaviour for soils treated with all tested concent rations. A. caliginosa preferred soils treated with 6.5, 60, 110, 180 mg arsenate kg −1 soil d.w., while the avoidance behaviour has been r corded only at 240 and 400 mg arsenate kg soil. d.w. This means that A. caliginosa individuals feed less when exposed to arsenate. On the contrary, the P. hawayana worms could be escaped into their deep vertical bu rrows when exposed to arsenate.

INTRODUCTION
Large quantities of contaminants have continuously been leaked into ecosystems as a consequence of urbanization and industrial processes (Begum et al., 2009). Heavy metal pollution is the case where the quantities of these elements in soils are higher than the natural environmental concentrations and is potentially harmful to biological life. Arsenic is a metalloid pollutant widelyintroduced into nature and the environment through industrial processes and agricultural practices (Button et al., 2009;2012). Samad et al. (2010) ranked arsenic in abundance as 20th in the earth's crust, 14th in seawater and 12th in the human body. There has been growing concern about the environmental effects resulting from arsenic compounds and, therefore, different countries have established various arsenic concentration limits for the protection of wild life in all ecosystems. Arsenic exhibits both metallic and non-metallic properties. In general, for metallic forms, arsenite (As 3 ) is considered more toxic than arsenate (As 5 ) (Molly et al., 2013). Since arsenic is a normal constituent of the environment, there is a need for effective monitoring and measurement of arsenic at arsenic-containing soil and waste sites. Arsenic occurs naturally in soils as a result of theweathering of the parent rock. Over 200 arsenic-containing minerals have been identified, with approximately 60% being arsenates, 20% sulphides and sulphosalts and the remaining 20% including arsenides, arsenites and oxides (Murciego et al., 2011). Ecotoxicological laboratory tests are considered a preliminary step in bioassays of environmental risk. Because of their relatively quick results, these tests can quantify the risks to animals posed by the use of certain substances in the soils of a given terrestrial ecosystem. Toxicity studies on soil fauna have not yet been carried Science Publications OJBS out for several heavy metals. Such tests are also required to implement rules that can effectively regulate agricultural protection products. Since earthworms are one of the most important biotic components in the soil, they have been utilized extensively in studies of the effects of heavy metals (Ander et al., 2009;2010a, 2010bButton et al., 2010;2012 ;Carbonell et al., 2009;Contreras-Ramos et al., 2009;Huang et al., 2010;Jones et al., 2009;Langdon et al., 2009;Natal-da-Luz et al., 2009;Oni and Hassan, 2013). Earthworms are known to play a major role in the mixing of soil constituents and are more susceptible to metal pollution than many other groups of terrestrial invertebrates. An avoidance response test has been used in many studies to assess the toxicity of contaminated soils to earthworms (Artuso et al., 2011;Kobeticova et al., 2010;Owojori and Reinecke, 2009). Most studies have evaluated arsenic toxicity in mammal cell lines and aquatic animal species. However, the studies of arsenic toxicity in terrestrial invertebrates, including earthworms are relatively limited.
The aim of this study was to characterize the effects of varying concentrations of arsenate on survival, growth, reproduction and behaviour of two earthworm species belonging to two different ecological categories: endogeic (A.caliginosa) and anecic (P.hawayana) under laboratory conditions.

Soil
Samples of a sandy loam soil have been collected from an orange orchard that has not been treated with inorganic as for 40 years. Background arsenic concentration in soil (control) was determined according to the methods of Anderson et al. (2013).

Chemicals
All reagents used were analytical grade and all aqueous solutions were prepared using distilled water. Inorganic sodium arsenate (Na 2 HASo 4 .7H 2 O) was purchased from Sigma-Aldrich, Egypt.

Experimental Animals
Clitellated specimens of two earthworm species A. caliginosa and P. hawayana were sampled in same duration in selected sites (non-polluted soil) by digging soil and were separated by hand sorting. Samples of each species were taken at the time of each sampling and placed in ventilated plastic boxes with their native soils and some leaf letter. The boxes containing earthworms and soil were returned to the laboratory in Faculty of Science, Zagazig University. The concentrations of arsenate used in the laboratory tests were determined through range finding tests. Experiments were started with an acute toxicity using increasing concentrations up to the limit of 400 mg kg −1 soil d. w. The chronic toxicity bioassays used sublethal concentrations based on the present definitive lethality tests. The avoidance tests used a different set of sublethal concentrations, lower than that used for chronic toxicity tests.

Acute Toxicity
Approximately 400 g of uncontaminated orchard soil were partially air dried, sieved (3 mm) and placed in circular plastic containers with a diameter 12.5 cm and a height of 9.5 cm such that each container contained soil to a depth 5-7 cm. The soil was then rewetted to a moisture content (55%) using distilled water (control) or a solution of sodium arsenate to give soil concentrations of 60, 110, 180, 240 and 400 mg arsenate kg −1 soil d. w. Three replicates of each concentration in addition to the control (untreated soil) were examined. The concentrations used were based on the results of pilot experiments (not reported here). Earthworms were washed and 20 individuals of each species were placed in each test container which was closed with plastic mesh. Lethal concentrations (96-h LC 50) of A. caliginosa and P. hawayana were assessed by probit analysis (Finney, 2009). After linearization of response curves by logarithmic transformation of concentrations, 95% confidence limits and slope function were calculated to provide a consistent presentation of toxicity data. The worms were fed cow manure each day during the 4 days of the test. In the last day of bioassays, worms were removed from the containers. Individuals that did not respond to the mechanical stimulation of the anterior portion of the body were recorded as dead.

Chronic Toxicity
Chronic toxicity effects of arsenate on earthworm reproduction and growth were assessed according to Alves et al. (2013). The bioassays were installed as in the acute toxicity tests which differed only in duration, concentrations and assessment methods. The soil was treated with sublethal concentrations 20, 30, 50, 100 and 150 mg arsenate kg −1 soil d. w., for A. caliginosaand P. hawayana. Three replicates of each concentration in addition to the control were used for 50 days. These concentrations were chosen on the basis of the data of previous acute toxicity test. Earthworms were washed Science Publications OJBS and weighed individually and 20 individuals of each species with 600 g native soil were placed in each test container which was closed with plastic mesh. In the 25 day of bioassay, worms were removed from the containers. Individuals that did not respond to the mechanical stimulation of the anterior portion of the body were recorded as dead. Live worms were washed and weighed and the difference between starting and ending body weight was calculated. For the next 25 days only the soils, juvenile worms and cocoons remained in the containers. On the 50th day, the containers were immersed in warm water (40±5°C) for 2 h and once the juveniles had emerged on the soil surface, the number of individuals generated was calculated. All worms were fed with cow manure once a week during time of experiment. In the chronic toxicity, the mean body weight difference and number of juveniles were calculated.

Earthworm's Behaviour
Avoidance tests were carried out following the recommendations of Alves et al. (2013). For both A. caliginosa and P. hawayana, the arsenate was tested at concentrations 10, 20, 30, 40 and 50 mg kg −1 soil d. w. with 3 replicates for each concentration. Plastic boxes (20×15×10 cm) were divided into two equal compartments with a plastic divider. To one compartment, 400 g of treated soil were added while the other compartment remained as a control (400 g of untreated soil). Immediately thereafter, the plastic divider was removed and 10 clitellated earthworms of each species were placed on the line separating the two compartments of the containers. Containers were covered with plastic mesh. No food was added during this experiment. After 48 h, the plastic dividers were inserted again and the soil in both compartments removed. The number of earthworms present in each container (treated and control) were counted. Worms that were along the dividing line between the two compartments were counted as 0.5 for each compartment. Percentage avoidance was calculated using the following equation: % avoidance = [(C-T)/N] ×100, where C is the number of worms in control soil, T is the number of worms in treated soil and N is the total number of worms at the beginning of experiment. Positive percentages indicate avoidance of the treated soil, a zero indicates no avoidance and the negative percentages indicate an attraction for the arsenic-treated soil.

Statistical Analysis
Analysis of data was carried out by student's t-test for comparing the means of experimental and control groups.

Acute Toxicity
In the control (background as concentrations in uncontaminated soil were 6.5 ± 0.3 mg kg −1 soil d. w.) of the acute toxicity tests, mortality of adult A. caliginosa and P. hawayanawas below 10%, achieving the requirements of bioassay validation. There were no significant differences between replicates for each treatment, therefore the data from the three replicates were pooled for statistical analyses. The 96-h continuous exposure LC50 for P. hawayana was significantly higher (233.43±42.45 mg arsenate Kg −1 soil. d. w.) than that of A. caliginosa (147.24±27.16 mg arsenate kg −1 soil d.w) (p<0.05, t-test).Surviving worms also had reduced body weight and in some cases, morphological abnormalities like, coiling and curling and lifting the body of A. caliginosahave been recorded.

Chronic Toxicity
In the chronic toxicity tests, the control showed means of 75 and 92 juveniles of A. caliginosa and P. hawayana, respectively. The number of produced A. calignosa juveniles were significantly (p<0.05, t-test) fewer than that of P. hawayana at the concentrations 180, 240 and 400 mg arsenate kg −1 soil d.w. Number of juveniles of P. hawayana were four times larger (40 individuals) than the number of juveniles of A. caliginosa (10individuals) at the concentration 400 mg arsenate kg −1 soil d.w. (Fig. 1). Examined P. hawayanashowed significant (p<0.05, t-test) reduction in body weight after 25 days exposure to concentration 60 mg arsenate kg −1 soil d.w. compared to the control while A. caliginosa individuals showed significant (p<0.05, ttest) reduction in body weight after 25 days exposure to all examined concentrations ( Fig. 2a and b).

DISCUSSION
Earethworms are key organisms in soil ecology. As ecosystem engineers their activity affects not only many important soil processes such as soil aeration, decomposition or nutrient availability, but they also promote soil biodiversity, soil fertility and soil health (Palm et al., 2013). In this study both acute and chronic toxicity effects of arsenate have been demonstrated. The 96-h LC50 (233.43±42.45 mg kg −1 soil d. w.) of P. hawayanawas significantly (p<0.05, t-test) higher than that of A. caliginosa (147.24±27.16 mg kg −1 soil d. w.). The difference between the acute toxicity of the two worms could be explained on the basis of the variety of their living and feeding habitats. A. caliginosa is an endogenic earthworm and the individuals of this species forage below the surface where they ingest large quantities of organic-rich soil and build burrows that are mainly horizontal in nature. Although they build permanent and vertical burrows that penetrate the soil deeply, the individuals of anceicspecies P. hawayana come to the surface to feed on partially decomposed litter, manure and other organic matter. Their burrows create microclimatic gradient and the worms can be found shallow or deep in their burrows depending on the prevailing conditions. The differences between the results reported in the literature and those of the present study are small and mostly attributable to different substrate composition and the earth worm species (Anderson et al., 2013).
Body weight loss may reflect reduced feeding by the worms as reported in other studies (Gomez-Eyles et al., 2009). In the present study, the body weight of A. caliginosa treated with arsenate concentrations (110-400 mg kg −1 soil d. w.) significantly (p<0.05, t-test) reduced in relation to the control while the body weight loss in p.hawayana was not affected by the arsenate concentrations except at 60 mg kg −1 soil d. w. This means that A. caliginosa individuals feed less when exposed to arsenate.
On the contrary, the anceic P. hawayana worms could be escaped into their deep vertical burrows when exposed to arsenate. However, Kreutzweiser et al. (2008) noted that worm feeding was similar in treated and control soils and attributed the reduction in biomass to physiological changes in worms. The lethal effectscould be attributed tothe blocking of nervous system receptors by pesticides. This blocking leads to an accumulation of acetylcholine which results in muscle and organ paralysis. In P. hawayana, the lowest concentration of arsenate (60 mg kg −1 soil d. w.) resulted in significant (p<0.05) less weight loss than the control (Fig. 3b) which could be the result of physiological stimuli caused by low concentrations of arsenate. Some authors have reported similar results and attributed it to a hormetic response which is defined as the ability of a substance to be toxic at high concentrations but stimulant at low concentrations (Zhang et al., 2009). Few number of researches have been performed on the impact of heavy metals on earthworms avoidance under laboratory conditions. The earth worm avoidance test, originally developed in USA, was selected because it is quick and easy to perform and it is known to be sensitive towards a wide range of chemicals. Natal-da-luz et al.
conducted avoidance tests with earthworms to demonstrate their feasibility as early screening tools for assessing the toxic potential of metal-polluted soils.
Summarizing the results ( Fig. 3a and b), it could be demonstrated that avoidance responses of P. hawayana is more sensitive to arsenate contamination than that of A. caliginosa. In this study, avoidance response of A. caliginosa occurred at a concentration 4 times (240 mg kg −1 soil d. w.) higher than that of P. hawayana (60 mg kg −1 soil d. w.). The ability of A. caliginosa to tolerate high levels of arsenate probably involves a combination of heritable and integrated physiological, morphological

Science Publications
OJBS and behavioral modifications. Increased bioimmobilization capacity may be the most likely physiological strategy for arsenate resistance in earthworms (Ander et al., 2010a).

CONCLUSION
In this study ecotoxicological laboratory tests have been conducted on two eco-physiological different earthworms to determine the impact of arsenate on the survival, reproduction and behaviour of the endogenic, A. caliginosa and the anecic, P. hawayana. Based on the results of this work, it is concluded that body weight loss may reflect reduced feeding by the worms. The body weight of A. caliginosa treated with arsenate significantly reduced in relation to the control while the body weight loss in P. hawayana was not affected by arsenate concentration except at 60 mg kg -1 soil d. w. For assessing the toxicity of arsenate, A. caliginosa and P. hawayana are ecologically relevant species and they are sensiive to arsenate applications. However, when a rapid and efficient screening is required, P. hawayana is much more convenient.


extfieldsofstudy: Biology Medicine

text:
A revision of the Larainae (Coleoptera, Elmidae) of Venezuela, with description of nine new species

Abstract The species of the riffle beetle subfamily Larainae occurring in Venezuela are revised. Examination of 756 specimens yielded 22 species in nine genera occurring throughout the country. Seven species are newly recorded from the country: Phanoceroides sp. 1, Phanocerus clavicornis Sharp, 1882, Phanocerus congener Grouvelle, 1898, Pharceonus volcanus Spangler & Santiago-Fragoso, 1992, Disersus dasycolus Spangler & Santiago-Fragoso, 1992, Disersus chibcha Spangler & Santiago-Fragoso, 1987, and Disersus inca Spangler & Santiago-Fragoso, 1992. Nine species are found to be new to science, which are here described: Hexanchorus dentitibialis sp. n., H. falconensis sp. n., H. flintorum sp. n., H. homaeotarsoides sp. n., H. inflatus sp. n., Phanocerus rufus sp. n., Pharceonus grandis sp. n., Pharceonus ariasi sp. n., Potamophilops bostrychophallus sp. n. Additionally, a key to species, distribution maps, and photographs and genitalia illustrations are provided for all species.

Introduction
The Elmidae, or "riffle beetles" are a widespread family of aquatic beetles common in a variety of running water habitats. Within Elmidae, there are two subfamilies, Larainae and Elminae. Species of Larainae are generally not found in the benthos, as with most elmine riffle beetles, but on water-splashed rocks and detritus just beyond the water's edge, carrying with them an air bubble under a thin film of water. As adults, they are agile fliers and enter and exit the water with great ease (Kodada and Jäch 2005). These unique habitat requirements make laraines difficult to collect unless one is seeking them out specifically.
Currently, there are 27 genera of laraines described, with eleven of these known from the Neotropical Region. Most work on the Neotropical fauna has been relatively recent, with Spangler andSantiago-Fragoso (1987, 1992) revising the Central American and West Indian fauna and three genera. Three other genera have been described from the Guiana Shield in southern Venezuela, Roraima Kodada & Jäch, 1999 (Mount Roraima), and Neblinagena Spangler, 1985 andHypsilara Maier &Spangler, 2011 (both from Cerro de Neblina). Additionally, new species of  and Potamophilops Grouvelle, 1896 have been described from Ecuador and Brazil, respectively (Monte and Mascagni 2012;Fernandes and Hamada 2012).
Recent fieldwork to Venezuela has yielded a large volume of laraine specimens (756 individuals) that were unidentifiable to species using current literature. I assembled material from other collections, including types, and discovered several more new species in that material. Herein I describe all of the new species found on these and prior expeditions, record several new distribution records for Venezuela, and present a key to species of Larainae in Venezuela.

Methods
Specimens were examined using an Olympus SZX7 dissecting microscope at various magnifications, from 8-56× magnification and described following terminology from Spangler and Santiago-Fragoso 1992. Specimens were photographed using a Canon EOS 70D with a Visionary Digital imaging system and photos were stacked using CombineZP image editing software (Hadley 2012).
The genitalia were extracted from relaxed specimens through the caudal opening in the abdomen. The genitalia were then cleared in heated potassium hydroxide for thirty minutes, rinsed with water, and temporarily mounted in glycerin gelatin (Zander 1997) for observation and illustration. The cleared genitalia were then placed in a plastic genitalia vial below the specimen for storage. Illustrations were made in pen and ink using a camera lucida attached to the compound microscope and scanned into the computer. Images were edited in Adobe® Illustrator® and Adobe® Photoshop®.
Label information in the material examined is quoted exactly from the original labels, with quotations ("…") indicating breaks between labels and semicolons (;) indicating line breaks. Where label data are ambiguous or incorrect, interpretations of label data are given in brackets ([...]).
Specimens are deposited in the following collections: Diagnosis. This species of Disersus can be distinguished from its congeners by the combination of an almost entirely bare metatibia (Fig. 12); blackish-brown femora; and indistictly produced elytral apices (Fig 9), as well as its large size (~8.5 mm) (see Spangler and Santiago-Fragoso 1987).
Intraspecific variation. This species varies slightly in size and coloration, from dark brown to nearly black. Additionally, the last abdominal ventrite of the male is notched, while the last abdominal ventrite of the female is slightly sinuate, and the elytral apices of the female are more acute than those of the male (see Spangler and Santiago-Fragoso 1987).
Habitat and distribution. Previously, D. chibcha was known only from a blacklight trap at Valle del Cauca, Colombia (Spangler and Santiago-Fragoso 1987). Sub-sequent collections of this species, given here, were from high gradient, medium-sized streams and waterfalls throughout the Mérida Andes in Venezuela (Fig. 1).
Associated species. No other laraine species were collected with D. chibcha.
Intraspecific variation. This species varies slightly in color and size, from a medium to dark brown. Females do not possess the patch of setae apicoventrally on the protibiae, and instead bear setae that resemble those of the other legs.
Habitat and distribution. Previously, this species was only known from a single specimen collected at blacklight trap in Pastaza Province, Ecuador. Somewhat surprisingly, this species is quite common in streams in the Mérida Andes of Venezuela above 1000m elevation, and seems to prefer stream margins (Fig. 2).
Associated species. A single species of Hexanchorus, H. flintorum sp. n. was collected at the same localities as Disersus dasycolus. Disersus spp. are often collected in conjunction with Hexanchorus spp. as they seem to prefer the same rocky cascades as habitat. Other aquatic beetles collected at the same localities include: Andogyrus spp. (Gyrinidae).
Diagnosis. Disersus inca can be distinguished from all other Disersus by the combination of the entirely pubescent metatibia, except for a narrow glabrous patch apically (Fig. 22) and the rounded elytral apices of the male.
Intraspecific variation. Members of this species vary slightly in size and color, from a reddish-brown to medium brown, and in total length from 6.6-7.6 mm. The female differs from the male in having slightly produced elytral apices and a rounded apical abdominal ventrite (see Spangler and Santiago-Fragoso 1987).
Habitat and distribution. Previously, D. inca was only collected in blacklight traps near montane streams in Ecuador, Colombia, and Peru (Spangler and Santiago-Fragoso 1987), this species is known to occur in the Cordillera Oriental in southwestern Venezuela from streams above 1000m in elevation (Fig. 1) Distribution. Species of Hexanchorus are widespread in the neotropics and can be found as far north as southern Mexico and as far south as Argentina. Additionally, a single species, Hexanchorus caraibus (Coquerel, 1851) is known from the West Indies south to Brazil , Passos et al. 2009, Segura et al. 2012.
Habitat. Often, Hexanchorus spp. can be found in the same habitats as Disersus spp. They are agile fliers and cling to rocks in fast flowing streams and rivers, flying into and out of the water quite readily.
Remarks. Only a single species of Hexanchorus (H. mcdiarmidi) was recorded from Venezuela prior to this study. Here I describe five new species from older museum material as well as specimens collected on recent expeditions to Venezuela.
Diagnosis. This species most closely resembles Hexanchorus mcdiarmidi, but can be distinguished from that species by the presence of a deep posteromedian impression on the pronotum (Fig. 27) and the extended elytral apices on the male (Fig. 23), which H. mcdiarmidi lacks. Additionally, species identity can be confirmed by the distinctive aedeagus, which is truncate in lateral view (Fig 26). This character does not occur in any other Hexanchorus species.
Head moderately coarsely, densely punctate; punctures separated by their diameter; cuticle microreticulate. Clypeus with anterior margin straight; angle on each side acute; lateral angles of clypeus with dense tuft of golden setae. Labrum with anterior margin entire and broadly rounded, covered with setae approximately twice as long as setae on head; lateral margins of clypeus with thick brush of curly, dark brown setae. Eyes hemispherical, narrowed posteriorly and bordered by long black curved setae ("eyelashes") that arise near dorsal and ventral sides of eyes and extend toward middle of eye. Antenna pubescent, filiform; basal antennomeres I and II testaceous ventrally, with dense recumbent setae and long, dark brown setae (Fig. 23). Antennae without club, but thickening slightly towards apex. Antennae long, reaching past transverse groove of pronotum (Fig. 23). Apical antennomeres dark brownish black, with dense recumbent setae. Apical antennomere square. Pronotum 0.8 mm long, 0.9 mm wide; with strong sublateral groove; lateral margins slightly sinuate; anterolateral angles square, not explanate; base of pronotum slightly sinuate and with broad lobe medially; posterolateral angles square, slightly explanate, declivous, depressed adjacent to each angle; discal area with fine, dense punctures, punctures separated by a distance equal to or less than their diameter; cuticle microreticulate ( Fig. 27). Pronotal disc lacking median longitudinal depression, with slight postero-medial impression; disc covered with short, dense, recumbent setae (Fig. 27). Lateral projection of hypomeron truncate. Prosternum short in front of procoxae; lacking tuft of setae apicomedially. Prosternal process triangular, broad at base and tapering to apex; disc slightly impressed, with V-shaped groove; lateral margins reflexed; middle concave; apex acute ( Fig. 24). Scutellum slightly longer than broad, flat, not distinctly elevated above the adjacent elytral intervals (Fig. 23). Mesoventrite short, depressed, with a deep, broad, V-shaped depression for reception of apex of prosternal process. Metaventrite with disc inflated on posterior three-fourths, finely punctate behind mesocoxae, punctures becoming more sparse laterally, with large, rounded depressions scattered on disc; with deep longitudinal groove on midline of disc, groove deepest and broadest on posterior third of disc; with short, dense pubescence; cuticular surface of metaventrite finely microreticulate.
Legs long and slender, dark brown (Fig. 24). Procoxae and metacoxae moderately widely separated; mesocoxae slightly more widely separated (Fig. 24). Protibia with deep excavation for reception of tarsi, with apical tooth (as in Fig. 46). Protarsus of male not expanded apicomedially (Fig. 24). Mesotibiae of male with medial pubescent area very long; lateral pubescent area only at extreme base (Fig. 23); with fine, short, nearly longitudinal carina on inner apex. Tarsal claws long and stout, light brown. Metafemur of male lacking internal glabrous patch.
Elytron with ten rows of fine punctures; punctures separated by a distance three to four times the diameter of the puncture; intervals with short, dense, recumbent pubescence and sparse erect setae; humeral area swollen (Fig. 23). Elytral striae visible apically. Elytron widening to about posterior two-thirds before converging to rounded apex. Apical third of elytron not inflated. Elytron without strong impression at basal third. Lateral bead of elytron slightly sinuate (Fig. 25). Elytra three times as long as pronotum; broadest point across humeri. Inner side of apex rounded; lateral margins smooth; humeri gibbous; elytral intervals slightly elevated; punctures on intervals no larger than finest punctures of head and pronotum and separated by 2-5 times puncture diameter.
Abdomen with five ventrites (Fig. 24). First three ventrites broadly, deeply depressed and distinctly carinate adjacent to metacoxae; carinae extending longitudinally behind metacoxae for almost entire length of first ventrite; cuticle densely covered with short, recumbent setae. Last ventrite shallowly and broadly emarginate (Fig. 24). Aedeagus wide, with truncate tip in lateral aspect, parameres reaching a little more than halfway up length of aedeagus (Fig. 26).
Female. Externally similar to male except elytral apices strongly pointed and slightly upturned (Fig. 23). Protibiae are slightly less curved than those of male. Mesotibiae without carina on inner apex. Metaventral disc not as deeply and less extensively concave. Abdominal sterna 1-3 convex, not concave.
Intraspecific variation. This species varies slightly in color, length (3.1-3.3 mm), and degree of setation.
Etymology. This species is named "dentitibialis", meaning "toothed tibia" to describe the protibia, which has an excavation for reception of the tarsus and an apical tooth.
Distribution and habitat. This species is only known from the type locality at Guayabita Creek, near Turmero, Aragua State, Venezuela (Fig. 3) Diagnosis. Hexanchorus falconensis can be distinguished from all other species of Hexanchorus by the distinctive aedeagus, with a "can-opener" tooth at apex (Fig. 31), and the extremely elongated elytral apices of the female (Fig. 28). Additionally, the pronotum lacks a median longitudinal impression (Fig. 28).
Head moderately coarsely, densely punctate; punctures separated by their diameter; cuticle microreticulate. Clypeus with anterior margin straight; angle on each side square; lateral angles of clypeus with dense turt of golden setae. Labrum with anterior margin entire and broadly rounded; labrum expanded laterally, covered with setae approximately three times as long as setae on head; lateral margins of clypeus with thick brush of curly, golden setae. Eyes hemispherical, narrowed posteriorly and bordered by long black curved setae ("eyelashes") that arise near dorsal and ventral sides of eyes and extend toward middle of eye. Antenna pubescent, clubbed; basal antennomeres I and II testaceous ventrally, with dense recumbent setae and long, dark brown setae (Fig. 29). Antennae serrate, thickening slightly towards apex (Fig. 28). Antennae long, reaching past transverse groove of pronotum. Apical antennomeres dark brownish black, with dense recumbent setae. Apical antennomere pointed (Fig. 29).
Pronotum 1.0 mm long, 0.9 mm wide; with strong sublateral groove; lateral margins slightly sinuate; anterolateral angles square, not explanate; base of pronotum slightly sinuate and with broad lobe medially; posterolateral angles obtuse, slightly explanate, declivous, depressed adjacent to each angle; discal area with fine, dense punctures, punctures separated by a distance equal to or less than their diameter; cuticle microreticulate (Fig. 28). Pronotal disc lacking median longitudinal depression, with slight postero-medial impression; disc covered with short, dense, iridescent setae (Fig. 28). Lateral projection of hypomeron reduced, nearly absent. Prosternum short in front of procoxae; lacking tuft of setae apicomedially (Fig. 29). Prosternal process broadly triangular, broad at base and slightly tapering to apex; disc slightly impressed, without V-shaped groove; lateral margins reflexed; middle concave; apex broadly acuminate (Fig. 29). Scutellum slightly longer than broad, strongly convex, distinctly elevated above the adjacent elytral intervals. Mesoventrite short, depressed, with a deep, broad, V-shaped depression for reception of apex of prosternal process. Metaventrite with disc inflated on posterior three-fourths, finely punctate behind mesocoxae, punctures becoming more sparse laterally, with large, rounded depressions scattered on disc; with deep longitudinal groove on midline of disc, groove deepest and broadest on posterior third of disc; with short, dense pubescence; cuticular surface of metaventrite finely microreticulate.
Legs long and slender, dark brown ( Fig. 29). Procoxae and metacoxae moderately widely separated; mesocoxae slightly more widely separated (Fig. 29). Protibia lacking excavation for reception of tarsi, lacking apical tooth. Protarsus of male strongly expanded apicomedially. Mesotibiae of male with medial pubescent area long; lateral pubescent area only at extreme base; with fine, short, nearly longitudinal carina on inner apex. Tarsal claws long and stout, light brown. Metafemur of male with small internal glabrous patch.
Elytron with ten rows of fine punctures; punctures separated by a distance three to four times the diameter of the puncture; intervals with short, dense, iridescent pubescence; humeral area swollen (Fig. 28). Elytral striae obscured apically. Elytron widening to about posterior two-thirds before converging to rounded and acute apex. Apical third of elytron not, or just barely inflated. Elytron without strong impression at basal third. Lateral bead of elytron sinuate. Elytra three times as long as pronotum; broadest point across humeri. Inner side of apex rounded; lateral margins smooth; humeri gibbous; elytral intervals slightly elevated; punctures on intervals no larger than finest punctures of head and pronotum and separated by 2-5 times puncture diameter.
Abdomen with five ventrites. First three ventrites broadly, deeply depressed and distinctly carinate adjacent to metacoxae; carinae extending longitudinally behind metacoxae for almost entire length of first ventrite; cuticle densely covered with short, recumbent setae. Last ventrite deeply and broadly emarginate. Aedeagus distinctive, with two small notches at tip ("can-opener" apex), parameres reaching more than halfway up length of aedeagus.
Female. Externally similar to male except elytral apices strongly acuminate and extended posteriorly (Fig. 28). Protibiae slightly less curved than those of male. Mesotibiae without carina on inner apex. Metaventral disc not as deeply and less extensively concave. Abdominal sterna 1-3 convex, not concave.
Intraspecific variation. This species varies slightly in color, length (4.0-4.3 mm), and degree of setation.
Etymology. This species is named "falconensis" in reference to the type locality in Falcón State, Venezuela.

Habitat and distribution.
Hexanchorus falconensis is only known from Cataratas del Hueque in Falcón State, Venezuela (Fig. 4). Specimens were collected in leaf packs and at stream margins, as well as in bulk samples and by scubbing rocks in the flowing water on flat, waterslide-like rocks. Associated species. This species was collected in association with Phanocerus congener. Other water beetles collected in the same habitat include: Lutrochus vestitus (Lutrochidae) (Maier & Short, 2013), Heterelmis spp., Microcylloepus spp., and Onychelmis spp. (Elmidae: Elminae), and the larvae of Psephenidae. Diagnosis. Hexanchorus flintorum can be distinguished from all other species of Hexanchorus that occur in Venezuela by the following combination of characters: pronotum without median longitudinal impression (Fig. 32), but with strong posteromedian impression; parameres of male short, reaching less than half the length of the aedeagus (Fig. 36).

Hexanchorus
Description. Holotype Male. Body elongate, subparallel, dorsum moderately convex. Length, 4.3 mm; greatest width, 1.5 mm. Body dark brown dorsally; venter dark brownish black (Fig. 32). Base of antenna, basal half of tibiae, and basal two thirds of femora light to medium brown (Fig. 33). Dorsal surface densely covered with short recumbent setae; ventral surface densely covered with short, recumbent setae and long, golden setae. Setae golden, and lacking greenish iridescence. Surface microreticulate, with dense fine punctures; fine punctures separated by distance equal to puncture diameter.
Head moderately coarsely, densely punctate; punctures separated by their diameter; cuticle microreticulate. Clypeus with anterior margin slightly concave; angle on each side acute. Labrum with anterior margin entire and gently concave; angle on each side acute, with row of dense, long golden setae. Eyes hemispherical, narrowed posteriorly and bordered by long black curved setae ("eyelashes") that arise near dorsal and ventral sides of eyes and extend toward middle of eye. Antenna pubescent, clubbed; basal antennomeres I and II medium to light brown, with long setae, longer than width of segments, and dense recumbent setae; antennal club very loose, just slightly thickened towards apex (Fig. 32). Antennae short, reaching transverse groove of pronotum (Fig. 33). Apical antennomeres dark brownish black, with dense recumbent setae. Apical antennomere rounded. Pronotum 1.1 mm long, 1.0 mm wide; with weak sublateral groove; lateral margins slightly sinuate; anterolateral angles obtuse, slightly explanate; base of pronotum slightly sinuate and with broad lobe medially; posterolateral angles obtuse, slightly explanate, declivous, depressed adjacent to each angle (Fig. 33); discal area with fine, dense punctures, punctures separated by a distance equal to or less than their diameter; cuticle microreticulate. Pronotal disc with slight median longitudinal drepression, with strong postero-medial impression; disc covered with golden setae. Lateral projection of hypomeron very acute, nearly absent. Prosternum short in front of procoxae; with tuft of dense golden setae apicomedially (Fig. 33). Prosternal process triangular, broad at base and tapering to apex; disc slightly impressed, without V-shaped groove; lateral margins reflexed; middle moderately longitudinally cariniform; apex narrow, acute (Fig. 33). Scutellum slightly longer than broad; flat, not at all convex, not distinctly elevated above the adjacent elytral intervals. Mesoventrite short, depressed, with a deep, broad, V-shaped depression for reception of apex of prosternal process. Metaventrite with disc inflated on posterior three-fourths, finely punctate behind mesocoxae, punctures becoming more sparse laterally, with large, rounded depressions scattered on disc; with deep longitudinal groove on midline of disc, groove deeper and broader on posterior third of disc (Fig. 33); with short, dense, short pubescence; cuticular surface of metaventrite finely microreticulate.
Legs long and slender, dark brown ( Fig. 33). Procoxae and metacoxae moderately widely separated; mesocoxae slightly more widely separated (Fig. 33). Protibia only with very slight excavation for reception of tarsi, lacking apical tooth. Protarsus of male not expanded apicomedially. Mesotibiae of male with medial pubescent area long; lateral pubescent area only at extreme base; with fine, short, nearly longitudinal carina on inner apex (Fig. 33). Tarsal claws long and stout, light brown. Metafemur of male with internal glabrous patch.
Elytron with ten rows of fine punctures; punctures separated by a distance three to four times the diameter of the puncture; intervals with fine, golden, dense pubescence; humeral area swollen (Fig. 32). Elytral striae obscured apically. Elytron widening to about posterior two-thirds before converging to acute apex. Apical third of elytron not inflated. Elytron without strong impression at basal third. Lateral bead of elytron slightly sinuate. Elytra 3.5 times as long as pronotum; broadest point across humeri. Inner side of apex straight (Fig. 32); lateral margins smooth; humeri gibbous; elytral intervals slightly elevated; punctures on intervals no larger than finest punctures of head and pronotum and separated by 2-5 times puncture diameter.
Female. Externally similar to male except inner apex of each elytron expanded posteriorly and slightly turned upward (Fig. 35). Protibiae slightly less curved than those of male. Metaventral disc not as deeply and less extensively concave. Abdominal sterna 1-3 convex, not concave.
Intraspecific variation. This species varies slightly in color, length (3.9-4.2 mm, and degree of setation.
Etymology. This species is named in honor of Dr. Oliver S. Flint and Mrs. Carol M. Flint who collected the specimens.

Distribution and habitat.
This species is only known from the mountains to the West of the Rio Chama valley near Ejido and Mérida, Mérida State, Venezuela, specifically, at Rio Montealban (Fig. 4). The largest series was collected from stream margins and pools at a river crossing north of Ejido.
Associated species. The laraine elmid species Disersus dasycolus and Pharceonus grandis were collected in the same samples as Hexanchorus flintorum. Other aquatic beetles collected at the same localities include: Andogyrus spp. (Gyrinidae).
Diagnosis. Hexanchorus homaeotarsoides is distinctive in the genus, as it is one of only two species to possess a median projection on the third abdominal ventrite of the female. It differs from the only other species which bears this character, Hexanchorus inflatus, by its evenly rounded elytra and aedeagus with a saw tooth apex. Additionally, the antennae are short, not extending behind transverse impression of pronotum; and the pronotum has a strong median longitudinal impression and the apical third of the elytra are not inflated posteriorly.
Head moderately coarsely, densely punctate; punctures separated by their diameter; cuticle microreticulate. Clypeus with anterior margin straight; angle on each side square. Labrum with anterior margin entire and gently rounded; angle on each side obtuse, covered with setae approximately twice as long as setae on head. Eyes hemispherical, narrowed posteriorly and bordered by long black curved setae ("eyelashes") that arise near dorsal and ventral sides of eyes and extend toward middle of eye, setae not as prominent as in other species. Antenna pubescent, clubbed; basal antennomeres I and II medium to light brown, with dense recumbent setae and dense brushy light brown setae, lacking long setae (Fig. 39). Antennal club very loose, just slightly thickened towards apex. Antennae short, reaching transverse groove of pronotum.
Pronotum 1.1 mm long, 1.0 mm wide; with strong sublateral groove (Fig. 41); lateral margins slightly sinuate; anterolateral angles square, not explanate; base of pronotum slightly sinuate and with broad lobe medially; posterolateral angles obtuse, slightly explanate, declivous, depressed adjacent to each angle (Fig. 41); discal area with fine, dense punctures, punctures separated by a distance equal to or less than their diameter; cuticle microreticulate. Pronotal disc with strong median longitudinal depression, with strong postero-medial impression (Fig. 41); disc covered with short, dense setae. Lateral projection of hypomeron truncate. Prosternum short in front of procoxae; without tuft of dense golden setae apicomedially (Fig. 38). Prosternal process broadly triangular, broad at base and slightly tapering to apex; disc slightly impressed, without V-shaped groove; lateral margins reflexed; middle flattened; apex broadly, acuminate (Fig. 38). Scutellum slightly longer than broad, strongly convex, distinctly elevated above the adjacent elytral intervals. Mesoventrite short, depressed, with a deep, broad, V-shaped depression for reception of apex of prosternal process. Metaventrite with disc inflated on posterior three-fourths, finely punctate behind mesocoxae, punctures becoming more sparse laterally, with large, rounded depressions scattered on disc; with shallow longitudinal groove on midline of disc, groove deepest and broadest on posterior third of disc; with short, dense pubescence; cuticular surface of metaventrite finely microreticulate.
Legs long and slender, dark brown. Procoxae and metacoxae moderately widely separated; mesocoxae slightly more widely separated. Protibia lacking excavation for reception of tarsi, lacking apical tooth. Protarsus of male expanded apicomedially. Mesotibiae of male with medial pubescent area long; lateral pubescent area only at extreme base; with fine, short, nearly longitudinal carina on inner apex. Tarsal claws long and stout, light brown. Metafemur of male with internal glabrous patch.
Elytron with ten rows of fine punctures; punctures separated by a distance three to four times the diameter of the puncture; intervals with short, dense pubescence; humeral area swollen (Fig. 37). Elytral striae visible apically. Elytron widening to about posterior two-thirds before converging to rounded apex (Fig. 37). Apical third of elytron not, or just barely inflated. Elytron without strong impression at basal third. Lateral bead of elytron strongly sinuate. Elytra 3.5 times as long as pronotum; broadest point across humeri. Inner side of apex angled; lateral margins smooth; humeri gibbous; elytral intervals slightly elevated; punctures on intervals no larger than finest punctures of head and pronotum and separated by 2-5 times puncture diameter.
Abdomen with five ventrites. First three ventrites broadly, shallowly depressed and distinctly carinate adjacent to metacoxae; carinae extending longitudinally behind metacoxae for almost entire length of first ventrite; cuticle densely covered with short, recumbent setae. Last ventrite deeply and broadly emarginate. Aedeagus unique in configuration, acute, with row of small teeth at apex; parameres long, extending past halfway up aedeagus (Fig. 42).
Female. Externally similar to male, except inner apex of each elytron acute and slightly turned upward (Fig. 37). Protibiae slightly less curved than those of male. Mesotibiae without carina on inner apex. Metaventral disc not as deeply and less extensively concave. Abdominal sterna 1-3 convex, not concave; apicomedial margin of third ventrite with distinct posterior projection (Fig. 40).
Intraspecific variation. This species varies slightly in color, length (4.1-5.1 mm), and degree of setation.
Etymology. The specific epithet, "homaeotarsoides" is a reference to the third ventrite of the female, which bears resemblance to the abdominal ventrite 4 of the male in the rove beetle (Staphylinidae) genus Homaeotarsus.
Distribution and habitat. This species is known only from the type locality at Rio Yameduaca in Amazonas State, Venezuela (Fig. 3). Nothing is known about its habits and exact microhabitat preferences.
Associated species. Hexanchorus inflatus sp. n. occurs in the same region of Venezuela, but no other species of laraine elmid has been collected at this locality. Diagnosis. This species can be distinguished from all other Hexanchorus species that occur in Venezuela by the following combination of characters: antennae long (Fig. 44), extending behind transverse impression of pronotum; pronotum lacking median longitudinal impression (Fig. 43); and protibia with deep excavation apically (Fig. 46). It most closely resembles Hexanchorus homaeotarsoides in distribution and that the female bears a median projection of the third ventrite, but can be distinguished from the former species by the distinctly inflated elytral apices (Fig. 45), and aedeagus with a smooth apex (Fig. 47).

Hexanchorus inflatus
Description. Holotype Male. Body elongate, subparallel, dorsum moderately convex (Fig 43). Length, 2.5 mm; greatest width, 1.1 mm. Body dark brown dorsally; venter dark brownish black (Fig. 44). Base of antenna and base of femora light to medium brown. Dorsal and ventral surface densely covered with short recumbent setae (Figs 43 and 44). Setae golden, and lacking greenish iridescence. Surface microreticulate, with dense fine punctures; fine punctures separated by distance equal to puncture diameter and coarse punctures confluent to separated by 1-3 times puncture diameter.
Head moderately coarsely, densely punctate; punctures separated by their diameter; cuticle microreticulate. Clypeus with anterior margin truncate; angle on each side broadly rounded. Labrum with anterior margin entire and gently arcuate; angle on each side broadly rounded, with row of dense, long golden setae. Eyes hemispherical, narrowed posteriorly and bordered by long black curved setae ("eyelashes") that arise near dorsal and ventral sides of eyes and extend toward middle of eye. Antenna pubescent, filiform, nearly serrate (Fig. 44); basal antennomeres I and II medium to light brown, with long setae, longer than width of segments, and dense recumbent setae; antenna lacking club. Antennae long, reaching past transverse groove of pronotum. Apical antennomeres dark brownish black, with dense recumbent setae (Fig. 44). Apical antennomere rounded.
Pronotum 1.2 mm long, 1.1 mm wide; lacking sublateral groove (Fig. 43); lateral margins slightly sinuate; anterolateral angles square, not explanate or depressed; base of pro- notum slightly sinuate and with broad lobe medially; posterolateral angles obtuse, slightly explanate, declivous, depressed adjacent to each angle; discal area with fine, dense punctures, punctures separated by a distance equal to or less than their diameter; cuticle microreticulate. Pronotal disc lacking median longitudinal depression, with weak postero-medial impression; disc with sparse, short setae (Fig. 43). Lateral projection of hypomeron acute. Prosternum short in front of procoxae; lacking tuft of setae and dense golden setae apicomedially (Fig.  44). Prosternal process triangular, broad at base and tapering to apex; disc with V-shaped groove; lateral margins reflexed; middle moderately longitudinally cariniform; apex narrow, acute (Fig. 44). Scutellum slightly longer than broad; very strongly convex, distinctly elevated above the adjacent elytral intervals. Mesoventrite short, depressed, with a deep, broad, V-shaped depression for reception of apex of prosternal process. Metaventrite with disc inflated on posterior three-fourths, finely punctate behind mesocoxae, punctures becoming more sparse laterally, with large, rounded depressions scattered on disc; with shallow longitudinal groove on midline of disc, groove deepest and broadest on posterior third of disc; with dense, short pubescence; cuticular surface of metaventrite finely microreticulate (Fig. 44).
Legs long and slender, dark brown (Fig. 45). Procoxae and metacoxae moderately widely separated; mesocoxae slightly more widely separated. Protibia with apical rounded excavation for reception of tarsi, with apical tooth (Fig. 46). Protarsus of male expanded apicomedially. Mesotibiae of male with medial pubescent area long; lateral pubescent area only at extreme base; with fine, short, nearly longitudinal carina on inner apex. Tarsal claws long and stout, light brown. Metafemur of male with internal glabrous patch.
Elytron with ten rows of fine punctures; punctures separated by a distance three to four times the diameter of the puncture; intervals with fine, short, dense pubescence; humeral area moderately swollen (Fig. 43). Elytral striae obscured apically. Elytron widening to about posterior two-thirds before converging to strongly rounded apex (Fig. 43). Apical third of elytron strongly inflated, most evident in lateral view (Fig.  45). Elytron with strong impression at basal third. Lateral bead of elytron straight. Elytra three times as long as pronotum; broadest point across humeri but only slightly broader than broadest point at apical third; inner side of apex rounded; lateral margins smooth; humeri gibbous; elytral intervals flat; punctures on intervals no larger than finest punctures of head and pronotum and separated by 2-5 times puncture diameter.
Female. Externally similar to male except inner apex of each elytron acute and slightly turned upward. Protibiae slightly less curved than those of male. Mesotibiae without carina on inner apex. Metaventral disc not as deeply and less extensively concave. Abdominal sterna 1-3 convex, not concave; apicomedial margin of third ventrite with distinct posterior projection.
Intraspecific variation. This species varies slightly from black to dark brown in color. There are differences in size (2.5-2.9 mm TL) and slight differences in punctation and setation.
Etymology. This species is named "inflatus" for the distinct elytra, which appear inflated posteriorly.
Habitat and distribution. This species is only known from specimens collected on an expedition by the University of Puerto Rico in 1950. They were collected at one locality from the upper Rio Cunucunuma in Amazonas State, Venezuela, north of Cerro Duida (Drake and Capriles 1952) (Fig. 4). The habits and microhabitat preferences of this species are unknown. Associated species. Hexanchorus homaeotarsoides sp. n. occurs in the same region of Venezuela, but no other species of laraine elmid has been collected at this locality. Diagnosis. Hexanchorus mcdiarmidi can be disinguished from all other Hexanchorus species in Venezuela by the presence of a greenish iridescent sheen on the dorsal setae (Fig. 48), the narrow parameres, and pronotum with only a shallow posteromedian impression (Fig. 48).

Hexanchorus mcdiarmidi
Intraspecific variation. This species varies slightly from black to dark brown in color, additionally, there may be slight variation in the greenish iridescence of the elytral setae. Hexanchorus mcdiarmidi has a purplish and orange iridescent sheen while submerged in alcohol (Short, pers. comm.). There is variation in size (2.9-3.4 mm TL) and slight differences in punctation among specimens.
Habitat and distribution. Hexanchorus mcdiarmidi is widespread in lower altitude (<300 m elevation) streams throughout western Venezuela (Fig. 4). They can be found in dense aggregations on water-splashed emergent rocks in small to medium sized swift-flowing streams and rivers with rocky substrate. Diagnosis. This genus can be distinguished from all other laraine genera by its small size (ca. 4.5 mm), and the presence of a shallow, wide, V-shaped groove across apical third of the pronotum, which lacks strong gibbosities or protuberances (Fig. 53). Distribution. Currently, Hypsilara is only known from near the base of Cerro de Neblina, Amazonas State and Gran Sabana, Venezuela (Fig. 2).
Habitat. From Maier and Spangler 2011 "These are known a small, shallow brook about one to two meters wide and with occasional pools about one meter deep, with a substratum of sand, boulders, and bedrock. This small tributary originates on Cerro de la Neblina and feeds the Rio Baria, which drains most of the massif. The high water marks and polished boulders along the stream bed indicate that in times of heavy rainfall, the brook becomes scoured by flash flooding. Paratypes were collected from similar small streams at high elevations.
Water quality data obtained by using colorimetric analyses of the brook at the type-locality are as follows; pH: 4, hardness: 0, oxygen: 9 ppm. The air temperature was 21°C and the water temperature was 17°C when the analyses were made." Diagnosis. This species can be distinguished from all other species of Hypsilara by the unique adeagus, possessing the following characters: long phallobase (ca. 0.6x as long as median lobe) and short parameres (ca. 0.67x as long as median lobe) (Čiampor et al. 2013).

Hypsilara breweri
Distribution and habitat. This species is known only from the type locality at a small, tannic stream flowing in degraded forest at Sierra de Lema, Gran Sabana, Ven-ezuela (Fig. 2). The species was collected from submerged woody debris, roots, and leaf litter (Čiampor et al. 2013) Notes. This species was described in a recent paper by Čiampor et al. (2013) and represents the second species described in the genus Hypsilara. A third species was also discovered at Auyán tepui, but not named, as it is known only from a single female (Fig. 2). Additionally, based on analysis of the cox1 gene, they found that this genus is likely to be closely related to Phanoceroides, an unusual laraine of north and central South America (Čiampor et al. 2013). Diagnosis. This species can be distinguished from all other described laraines by the following combination of characters: small size (ca. 4.5 mm), the presence of a shallow, wide, V-shaped groove across apical third of the pronotum (Fig. 53), and pronotum 1.3 mm long, and 1.5 mm wide, with posterolateral angles obtuse.
Intraspecific variation. This species exhibits only minor variations in length, which ranges from 4.2 to 4.5 mm, and varies from a medium brown to light brown in color. Additionally, the parameres can be straight to slightly curved.
Distribution and habitat. This species is known only from the type locality at Cerro de Neblina, Amazonas State, Venezuela (Fig. 2), see genus description for detailed habitat information.
Associated species. The Cerro de Neblina endemic species Neblinagena prima was the only laraine elmid species collected in association with Hypsilara royi.
Distribution. Neblinagena species are endemic to the Guiana Shield region in eastern Venezuela, though presumably they also occur across the borders in Guyana and Brazil (Fig. 5).
Habitat. Based on the collecting events of specimens examined, Neblinagena spp. seem to prefer small, high elevation streams (>400m elevation), with rocks and forested cover. They have been found in leaf packs and clinging to rocks in the water flow. Their habits are most likely extremely similar to those of Disersus spp. and Hexanchorus spp.  Diagnosis. Neblinagena doylei can be distinguished from N. prima by its range, which does not overlap with the range of the latter. Additionally, in N. doylei the pronotal longitudinal carinae are entire and the oblique furrow of the pronotum forms a 30° angle relative to the median longitudinal furrow (Fig. 57), whereas in N. prima the pronotal lateral carinae are obscured anteriorly and the oblique furrows form a 45° angle relative to the median longitudinal furrow (Fig. 61). Neblinagena doylei is also slightly larger than its congener.

Nebilinagena doylei
Intraspecific variation. This species varies slightly in size (5.5-6.6 mm) and in coloration -from dark brown to black.
Distribution and habitat. Neblinagena doylei can be found throughout the eastern part of Venezuela, in and around the Gran Sabana, in Bolívar and Amazonas States ( Diagnosis. Neblinagena prima can be distinguished from N. doylei by its range, which does not overlap with the range of the latter. Additionally, the pronotal lateral carinae of N. prima are obscured anteriorly and the oblique furrows form a 45° angle relative to the median longitudinal furrow (Fig. 61), whereas in N. doylei the pronotal longitudinal carinae are entire and the oblique furrow of the pronotum forms a 30° angle relative to the median longitudinal furrow (Fig. 57).
Intraspecific variation. This species varies slightly in size (6.0-6.3mm) and in coloration -from dark brown to black. Habitat and distribution. This species appears to be endemic to Cerro de Neblina, and is restricted to the highlands, unlike its congener, Neblinagena doylei, which is widespread in lower areas (<1000m) of Bolivar State, Venezuela (Fig 5). Neblinagena prima was collected in leaf packs and between boulders in small mountain streams on Cerro de Neblina (Spangler 1985).
Associated species. This species is associated with the other, highly unusual, Cerro de Neblina endemic, Hypsilara royi, and was collected in the same habitats.
Distribution. This genus is known from Manaus, Amazonas State, in the Amazon river basin in Brazil and from Tobogan de la Selva, Amazonas State, in the Orinoco River drainage in Venezuela, and probably occur throughout the Southern Venezuela and Northern Brazil. There have also been literature reports of Phanoceroides spp. from as far west as Cordillera de Vilcabamba, Peru, but this record has not been confirmed by me (Acosta et al. 1998).
Habitat. Phanoceroides species have unique habitat requirements in the subfamily Larainae, in that they remain fully submerged and are found in the benthos of streams, as opposed to water-splashed surfaces in streams as others in Larainae (Hinton 1939).
Notes. The genus Phanoceroides is rather interesting among the Larainae, in that while it bears superficial resemblance to beetles in the subfamily Elminae, in their fully aquatic habits and in the presence of a dense, hairy plastron on the ventral surface, anatomically, they are most similar to the Larainae, and therefore they are included in this work. Whether this is a case of convergent evolution or the retention of plesiomophic characters is unknown and it deserves further study, and this species may provide insights into the evolution of laraine Elmidae. Distribution and habitat. In Venezuela, this species has only been collected at a single locality, Caño Coromoto, at El Tobogan de la Selva (Fig. 3). They were found in leaf packs and in benthic stream samples between the cascades. Additionally, specimens are known to come to UV lights.
Associated species. No other species in Larainae has been collected with this Phanoceroides species, however, other aquatic beetles collected in the same habitat include: Tyletelmis spp., Heterelmis spp., Gyrelmis spp., Neoelmis spp., Neolimnius spp., Pilielmis spp. Notes. This species will be described in a later publication.  Figs 6,7,8,66,67,68,69,70,71,72,73,74,75,76. Diagnosis. This genus can be distinguished from all other genera of Larainae in Venezuela by its small size and pronotum which lacks a transverse groove (Fig. 68). Distribution and habitat. Phanocerus spp. can be found throughout Central America and northern South America. They are fast fliers and congregate in leaf packs and on water-splashed detritus in streams, waterfalls, and rivers.  Diagnosis. Phanocerus clavicornis can be separated from all other species of Phanocerus by the shape of the pronotum (Fig. 68). The pronotum is narrow in P. clavicornis, with narrow anterolateral angles, which are not explanate. Additionally, the setose patch at the base of the mesotibia is short (Fig. 66).

Phanocerus clavicornis
Intraspecific variation. This species varies a great deal in color and size, from 2.0-2.7 mm in size, and from dark brown to medium brown in color. Occasional specimens can have a reddish cast, but this is rare.
Distribution and habitat. The range of P. clavicornis is very large, and it is the most widely distributed laraine species in the Western Hemisphere. It occurs from Texas, in Southwestern United States, south to Amazonas State, Venezuela; it is also the most widely distributed in Venezuela, occurring throughout the country, excepting Los Llanos region in the central part of Venezuela (Fig. 6).That makes it the only species of laraine that crosses the Llanos and occurs on both the Guiana Shield and in the Northern Andes.
The habitat of P. clavicornis is similar to that of any other species of Phanocerus, it can be found in small to medium sized streams and rivers, in the leaf packs and on partially submerged detritus and woody debris.
Associated species. Numerous species of aquatic Coleoptera have been collected with this common laraine elmid, however, they will not be listed here, since they are so widespread. Diagnosis. Phanocerus rufus can be distinguished from all other species of Phanocerus by the combination of its large size (2.7-3.5 mm), reddish coloration (Fig. 72), distinctive pronotal shape, that is 1.6x as wide as long (Fig. 75), and the presence of a short setose patch at base of mesotibia (Fig. 74).
Head moderately coarsely, densely punctate; punctures separated by their diameter; cuticle microreticulate. Clypeus with anterior margin rounded. Fronto-clypeal suture deep and curved. Labrum with anterior margin entire and gently rounded, narrower than clypeus; angle on each side obtuse, covered with setae approximately twice as long as setae on head. Eyes protruding only slightly laterally; separated by a distance about 3x the eye-width; bordered by short dark brown curved setae ("eyelashes") that arise near dorsal and ventral sides of eyes and extend toward middle of eye, setae not as prominent as in other genera. Antenna 11 segmented, densely pubescent, slightly clubbed; basal two antennomeres with dense, medium-brown, brushy setae, thicker in width than proceeding antennomeres, with dense recumbent setae and dense brushy light brown setae. Antennal club of six antennomeres, compact, wide, quite thickened towards apex. Antennae very short, just barely reaching transverse groove of pronotum. Apical five antennomeres reddish-brown, with dense recumbent setae. Apical antennomere rounded.
Pronotum overall smooth, 1.6x as wide as long; widest at basal third; anterior width roughly two thirds the posterior width; anterior margin strongly convex over base of head; base tri-sinuate (Fig. 74). Pronotum with a sublateral groove, which joins deep anterolateral fovea near the anterior margin; anterolateral margins explanate; base with two small foveae anterior to scutellum; lateral margins strongly sinuate, nearly at right angles at basal third, strongly gibbous (Fig. 74); surface similarly punctate to head. Hypomeron oblique. Scutellum flat, broader than long; posterior angle square. Prosternum long in front of procoxae. Anterior margin reflexed ventrally. Prosternal process narrowly triangular, broad at base and tapering to apex; disc with strong median carina, lateral margins reflexed; apex strongly acuminate (Fig. 73). Mesoventrite short, depressed, with a deep, narrow, U-shaped depression for reception of apex of prosternal process (Fig. 73). Metaventrite with disc inflated on posterior three-fourths, finely punctate behind mesocoxae; with deep, impressed longitudinal groove on midline of disc, groove deepest and broadest on posterior third of disc (Fig. 73); with short, dense pubescence; cuticular surface of metaventrite finely microreticulate. Elytra more than 3.4x as long as pronotum; lateral margins slightly sinuate; humeri and base adjacent to scutellum slightly gibbous; lateral margins smooth; apex smoothly rounded. Each elytron with 10 coarse striae formed by a row of large, coarse punctures separated by more than three times their diameter; striae slightly impressed becoming narrower and more shallow towards the apex; strial punctures coarse basally, becoming progressively finer towards apex; striae 3 and 4 not converging sub-apically; intervals flat ( Fig. 72). Elytral surface with dense, golden recumbent pubescence and dense, erect hair-like setae.
Female. Externally similar to male except slightly larger in size, protibiae slightly less curved than those of male. Metaventral disc not as deeply and less concave. Apical abdominal ventrite with less dense setae than male.
Intraspecific variation. This species varies slightly in color, from dark reddishbrown to medium reddish-brown, length (2.7-3.5 mm), and degree of setation.
Distribution and habitat. This species has only been collected at the type locality at Rio Castaño, a small river in cloud forest on the interior slopes of Henri Pittier National Park, in Aragua State, Venezuela (Fig. 8). They were collected on logs in the stream and in leaf packs.
Etymology. This species is named Phanocerus rufus, in reference to the slightly reddish cast of the cuticle.
Associated species. Phanocerus rufus was found in crevices on submerged logs along with the lutrochid, Lutrochus acuminatus (Maier and Short 2013).
Other material examined (Not Assigned to species -all female, likely new species).
Distribution. Pharceonus species occur throughout southern Central America and northern South America, from Costa Rica south to Peru (pers. obs.).
Description. Holotype male. Body elongate, sub-parallel, moderately convex. Total length 3.3 mm, greatest width 1.3 mm. Cuticle dark brown, base of maxillary palpus, six basal antennomeres, femora, and tarsi testaceous (Fig. 78). Dorsal surface with dense, erect brownish hair-like setae and denser and finer, golden, recumbent setae (Fig. 77). Surface microreticulate, with dense fine punctures. Head moderately coarsely, densely punctate; punctures separated by their diameter; cuticle microreticulate. Clypeus with anterior margin truncate. Fronto-clypeal suture deep and slightly curved. Labrum with anterior margin entire and straight; angle on each side rounded, covered with golden setae approximately twice as long as setae on head. Eyes protruding only slightly laterally; separated by a distance about three times the eye-width; bordered by long dark brown curved setae ("eyelashes") that arise near dorsal and ventral sides of eyes and extend toward middle of eye, setae not as prominent as in other genera. Antenna 11 segmented, pubescent, slightly clubbed; basal two antennomeres with long, brown, hair-like setae, thicker in width than proceeding antennomeres, with dense recumbent setae and dense brushy light brown setae (Fig. 77). Antennal club of six antennomeres, compact, thickened towards apex. Antennae short, reaching transverse groove of pronotum. Apical five antennomeres dark brownish black, with dense recumbent setae. Apical antennomere rounded.
Pronotum heavily sculptured, wider than long (1.1 mm and 1.0 mm, respectively); widest at basal third; anterior width two thirds the posterior width; anterior margin strongly convex over base of head; base tri-sinuate (Fig. 77). Pronotum with a shallow sublateral depression on each side extending from a deep anterolateral fovea near the anterior margin towards the base, where it is joined to sub-basal, transverse and bisinuate shallow depression; a short medial longitudinal and superficial groove joins the sub-basal and transverse depression with a strong tranverse and bisinuate depression at apical third; surface similarly punctate to head (Fig. 77). Pronotal base with strong median gibbosity anterior to scutellum. Hypomeron oblique (Fig. 79). Scutellum flat, broader than long, elevated posteriorly; posterior angle obtuse. Prosternum long in front of procoxae; with tuft of long, golden setae apicomedially. Anterior margin reflexed ventrally. Prosternal process scutiform, broad at base and tapering to apex; disc slightly impressed, lateral margins reflexed; middle convex; apex acuminate ( Fig. 78). Mesoventrite short, depressed, with a deep, narrow, V-shaped depression for reception of apex of prosternal process. Metaventrite with disc inflated on posterior threefourths, finely punctate behind mesocoxae; with deep, impressed longitudinal groove on midline of disc, groove deepest and broadest on posterior third of disc; with short, dense pubescence; cuticular surface of metaventrite finely microreticulate (Fig. 78).
Elytra more than three times as long as pronotum; lateral margins slightly sinuate; humeri and base adjacent to scutellum strongly gibbous; lateral margins smooth; apex rounded ( Fig. 79). Each elytron with 10 coarse striae formed by a row of deep punctures well separated by more than three times their diameter; striae slightly impressed becoming narrower and more shallow towards the apex; strial punctures coarse basally, becoming progressively finer towards apex; striae 3 and 4 converging sub-apically; intervals flat (Fig. 77). Elytral surface with dense, golden pubescence.
Legs thin and short. Pro-, meso-and metatibiae with very short fringe of tomentum extending from about mid-tibia to nearly the tip. Surface of legs entirely pubescent, including mesotibiae. Mesotibia with small glabrous patch basally. Apical tarsomere of all legs with glabrous patch dorsally.
Female. Externally similar to male except slightly larger in size, elytral gibbosities more producted, and elytral sutural stria slightly inflated in apical third. Protibiae slightly less curved than those of male. Metaventral disc not as deeply and less concave.
Abdominal ventrite IV lacking V-shaped carina. Apical abdominal ventrite with less dense setae than male.
Intraspecific variation. This species varies slightly in color, from dark brown to medium brown, length (3.5-4.1 mm), and degree of setation.
Etymology. The specific epithet "ariasi" is a patronym in honor of Mr. Quintin Arias, who helped to collect many of the specimens of this species.
Distribution and habitat. This species is limited to the type locality at Cascada Velo de la Novia and from a nearby stream 12 km southeast of Santo Domingo, in Mérida State, Venezuela (Fig. 8). The specimens were found clinging to waterlogged woody debris in the river.
Associated species. No other laraine species were collected with P. ariasi. Diagnosis. This species can be distinguished from all other species of Pharceonus by its large size (3.5-4.3 mm), slightly reddish color (Fig. 81), wide genitalia (aedeagus + phallobase) (3.7x as long as wide) (Fig. 84), and pronotum with a deep and strongly bisinuate transverse impression across apical third (Fig. 83).
Head moderately coarsely, densely punctate; punctures separated by their diameter; cuticle microreticulate. Clypeus with anterior margin rounded. Fronto-clypeal suture deep and curved. Labrum with anterior margin entire and gently rounded; angle on each side obtuse, covered with setae approximately twice as long as setae on head. Eyes protruding only slightly laterally; separated by a distance about 3.5x the eye-width; bordered by long dark brown curved setae ("eyelashes") that arise near dorsal and ventral sides of eyes and extend toward middle of eye, setae not as prominent as in other genera. Antenna eleven segmented, pubescent, slightly clubbed; basal two antennomeres with long, brown, hair-like setae, thicker in width than proceeding antennomeres, with dense recumbent setae and dense brushy light brown setae. Antennal club of six antennomeres, compact, thickened towards apex (Fig. 81). Antennae short, reaching transverse groove of pronotum (Fig. 81). Apical five antennomeres dark brownish black, with dense recumbent setae. Apical antennomere rounded.
Pronotum heavily sculptured, as wide as long (0.9 mm and 0.9 mm, respectively); widest at basal third; anterior width two thirds the posterior width; anterior margin strongly convex over base of head; base tri-sinuate (Fig. 83). Pronotum with a sublateral depression on each side extending from a deep anterolateral fovea near the anterior margin towards the base, where it is joined to sub-basal, transverse and bisinuate depression; a short medial longitudinal and superficial groove joins the subbasal and transverse depression with a strong tranverse and bisinuate depression at apical third; surface similarly punctate to head. Pronotal base with strong median gibbosity anterior to scutellum (Fig. 83). Hypomeron oblique. Scutellum slightly convex, broader than long, elevated posteriorly; posterior angle square. Prosternum long in front of procoxae; with tuft of long, golden setae apicomedially. Anterior margin reflexed ventrally. Prosternal process narrowly triangular, broad at base and tapering to apex; disc slightly impressed, lateral margins reflexed; middle convex; apex acuminate (Fig. 82). Mesoventrite short, depressed, with a deep, narrow, Vshaped depression for reception of apex of prosternal process. Metaventrite with disc inflated on posterior three-fourths, finely punctate behind mesocoxae; with deep, impressed longitudinal groove on midline of disc, groove deepest and broadest on posterior third of disc; with short, dense pubescence; cuticular surface of metaventrite finely microreticulate (Fig. 82).
Elytra more than three times as long as pronotum; lateral margins slightly sinuate; humeri and base adjacent to scutellum strongly gibbous; lateral margins smooth; apex rounded. Each elytron with ten coarse striae formed by a row of large punctures well separated by more than three times their diameter; striae slightly impressed becoming narrower and more shallow towards the apex; strial punctures coarse basally, becoming progressively finer towards apex; striae 3 and 4 converging sub-apically; intervals flat ( Fig. 81). Elytral surface with dense, golden pubescence.
Legs thin and short (Fig. 81). Pro-, meso-and metatibiae with very short fringe of tomentum extending from about mid-tibia to nearly the tip. Surface of legs entirely pubescent, including mesotibiae. Mesotibia with small glabrous patch basally. Apical tarsomere of all legs with glabrous patch dorsally.
Female. Externally similar to male except slightly larger in size, elytral gibbosities more producted, and elytral sutural stria slightly inflated in apical third (Fig. 81). Protibiae slightly less curved than those of male. Metaventral disc not as deeply and Intraspecific variation. This species varies slightly in color, from dark reddishbrown to medium reddish-brown, length (3.5-4.2 mm), and degree of setation.
Distribution and habitat. Pharceonus grandis has been collected only in the Mérida Andes in Venezuela (Fig. 5), at stream margins and in bulk benthic samples.
Etymology. Pharceonus grandis is named after the Latin "grandis", meaning large, referring to its large size.
Associated species. No other laraine species were collected with Pharceonus grandis. The following aquatic beetle taxa were collected at the same localities as P. grandis: Andogyrus spp. Diagnosis. This species can be distinguished from all other species of Pharceonus by its small size (3.1-3.5 mm), dark brown color, genitalia (aedeagus + phallobase) of medium width (4.3× as long as wide), and pronotum with only a shallow transverse impression across apical third (Fig. 87).
Intraspecific variation. This species varies slightly in color, from dark brown to medium brown, and size, from 3.1-3.5 mm.
Distribution and habitat. This species is found on roots in small to medium forested streams, and on roots in seeps in the Sierra de Perija in Venezuela (Fig. 5). This appears to be the southern extent of its range. Outside of Venezuela, this species is known from as far north as Costa Rica. Specimens have been collected in leaf packs and in the benthos in shallow streams.
Distribution. Potamophilops has been recorded from as far south as northern Argentina, Mato Grosso and São Paulo States, Brazil (Spangler and Santiago-Fragoso 1987; riorly. Labrum, especially on anterior half, densely punctate; anterior margin shallowly and broadly emarginate, and densely fringed with long, fine, golden, hair-like setae; anterolateral angles rounded and greatly expanded laterally. Pronotum widest at base; length, 1.5 mm; width, 1.7 mm; sides arcuate; anterolateral angles obtuse, with distinct constriction posterolaterally of each angle resulting from deep transverse impression across apical third of pronotum (Fig. 91); apex arcuate; base strongly bisinuate; with a shallow fovea on each side of midline a short distance in front of scutellum; posterolateral angles obtuse; with a deep, broad de- pression adjacent to each angle, angled reflexed dorsally; surface with deep transverse impression across apical third; midline convex behind transverse impression (Fig. 91); discal area finely densely punctate, punctures separated by a distance equal to or less than their diameter.
Prosternum very short in front of procoxae. Prosternal process wide, elongate, apex with median process extending posteriorly further than sides (Fig. 89). Mesoventrite with moderately deep U-shaped depression for reception of apex of prosternal process. Metaventrite convex on each side of midline, depressed, with a glabrous line posteromedially between metacoxae (Fig. 89); surface microreticulate and punctate; punctures on convex surface fine and dense, separated by a distance equal to or less than their diameter; punctures sparser laterally.
Elytron with 10 rows of fine, nearly confluent punctures, punctures separated by a distance less than their diameter; intervals finely densely punctate, punctures separated by distance about equal to their diameter and obscured by dense pubescence; humeral area strongly tumid; sides of elytra distinctly margined and almost parallel; apex slightly dehiscent, evenly arcuate laterally and terminating in a pointed, upturned apex (Fig. 88).
Female. Similar to male except last abdominal ventrite is subtruncate and the elytral apices are slightly more produced and elongate than in the male.
Intraspecific variation. This species varies slightly in color from dark brown to black and size, (6.0 mm-6.8 mm).
Distribution and habitat. This species has been found in rivers at lower elevations (<500m) throughout the Guiana Shield region in Venezuela, and presumably occurs in northern Brazil and Western Guyana as well (Fig. 1).
Associated species. This species has been found in association with Lutrochus cauraensis (Lutrochidae) at Kanarakuni, Venezuela (Maier and Short 2013 Distribution. Roraima is known only from the type locality on Mount Roraima in Bolívar State, Venezuela (Fig. 2).
Habitat. See species account for habitat information.


Dynamics and spike trains statistics in conductance-based Integrate-and-Fire neural networks with chemical and electric synapses

We investigate the effect of electric synapses (gap junctions) on collective neuronal dynamics and spike statistics in a conductance-based Integrate-and-Fire neural network, driven by a Brownian noise, where conductances depend upon spike history. We compute explicitly the time evolution operator and show that, given the spike-history of the network and the membrane potentials at a given time, the further dynamical evolution can be written in a closed form. We show that spike train statistics is described by a Gibbs distribution whose potential can be approximated with an explicit formula, when the noise is weak. This potential form encompasses existing models for spike trains statistics analysis such as maximum entropy models or Generalized Linear Models (GLM). We also discuss the different types of correlations: those induced by a shared stimulus and those induced by neurons interactions.

Introduction
Communication between neurons involves chemical and electric synapses. Electric synapses transmission is mediated by gap junctions providing direct communication between cells, allowing faster communication than chemical synapses. Electrical coupling between cells can be found in many parts of the nervous system.
At the network level, electric synapses have several prominent effects such as neural synchronization, and generation of neural rhythms. Additionally, they are responsible for sharp peaks in the auto-correlation of ganglion cells in the retina. Dealing with spike population coding, interactions between neurons highly constrain the collective spike response of a neural assembly to stimuli. Thus, unveiling the respective effect of chemical and electric synapses on spike responses is a mandatory step towards a better understanding of spike coding.
Can we have a reasonable idea of what is the spike train statistics and how it depends on stimulus and connectivity studying a neural network model considering chemical and electrical synapses? This work answers this question.

Methods and results
In [1] we have analyzed mathematically the collective effects of chemical and electric synapses in a conductance-based Integrate-and-Fire neural network, where conductances depend on spike history [2]. We have also analyzed spike train statistics and show that it is described by a non-stationary Gibbs distribution whose potential can be approximated with an explicit formula, when the noise is weak. This result is compared to maximum entropy models currently used in the literature of spike train analysis. The Gibbs potential includes existing models for spike trains statistics analysis such as maximum entropy models or Generalized Linear Models (GLM). The potential has an infinite range (infinite memory), although Markovian approximation can be proposed, replacing the exact potential by a potential with a finite range. The Gibbs distribution obtained in our model is quite more complex than Ising model or Generalized Linear Models used in retinal spike train analysis [3]. Especially, it involves spatio-temporal spike patterns and is non stationary. We identified the role of gap junctions on history dependence and in the spike train statistics. We also discuss the different types of correlations: those induced by a shared stimulus and those induced by chemical and electric interactions between neurons.

Conclusion
This work suggest that electric synapses could have a strong influence in spike train statistics of biological neural networks, especially in the retina where gap junctions connections between several cells-type (e.g. amacrine and ganglion cells or amacrine-bipolar) are ubiquitous. The main observation is that considering gap junctions the probability of spike patterns does not factorize as a product of marginal, per-neuron, distributions. Therefore there is absolutely now way to defend that neurons in this model act as independent sources. Additionally, correlations mainly result from the chemical and electrical interactions (correlations persist even if there is no external current / stimulus), thus gap junctions play an important role in correlating the network even in absence of stimulus. This work provides a firm theoretical ground for recent studies attempting to describe experimental rasters in the retina as well as in the parietal cat cortex by Gibbs distributions using the maximum entropy principle.