common river species small freshwater water gill aquatic family widely distributed species occurs europe thick shell coloration pattern shell variable lives freshwater water rivers lakes stones feeds mainly grazing populations species spreading reach thousands square meter females lay egg contains large number eggs capsule reach sexual maturity year total lifespan years taxonomy originally described original text type description latin short reads follows means english number shell teeth inhabits rivers europe later species moved genus fact type species genus colleagues designated english translation published subspecies subspecies described recognized authors described freshwater environment considered synonym described water separate species originally named study proved status subspecies regarded synonym called forms form form differ morphology ecology reproductive strategy behaviour probably lake considered subspecies consider distinct species shows relationships genus shows sister group clade clade split lake existed species living water include apparently closely related distribution exact type locality species unknown probably main river considered type locality habitat suggest water environment distribution species considered european reality species occurs western central occurrence scattered europe alps regions immediately north alps species live norway siberia widespread distribution species genus fact widely distributed species entire family species threatened mainly river engineering water pollution densely populated regions species population trend overall stable declining areas germany areas expanding example danube river rhine river 1970s came close local extinction water pollution subsequently water quality improved decades leading recovery species extinct rhine unknown reason late 1990s rhine probably ship transport analysis based gene shown probably originated danube europe species occurs widely western_europe widespread north ireland living irish streams rivers lives great_britain including isle netherlands belgium found france switzerland considered critically endangered south occurs spain portugal species restricted springs central europe species lives recorded czech_republic extinct findings river near recent findings shells took place occurs poland slovakia non indigenous hungary provided detailed distribution germany indigenous distribution included large rivers rhine main species highly endangered germany stark species found denmark sweden far north found coasts finland known found alive species reaches baltic_sea northernmost distribution genus northernmost species eastern_europe occurs estonia lithuania russia western russia found ukraine non indigenous recorded area occurs lives albania romania bulgaria croatia macedonia albania occurs lake spans border countries subspecies found mainland greece crete known occur mainland italy occurs montenegro serbia asia africa asia found turkey found iran provinces records iran listed africa species occurs algeria possibly probably morocco records authors consider reliable instead species brown recognized species northwestern africa prehistoric found archaeological site cave portugal site years age shells late found czech_republic ancestral range region southern ukraine romania hungary suggested species northern italy greece turkey second phase spain france germany finally british isles sweden baltic_sea german summarized distribution species pleistocene description shell somewhat depressed usually low strongly including larger specimens usually eroded width adult shell usually reach height shell mean values vary populations depending environment maximum width shell water populations water shells somewhat shorter reaching maximum weight shell freshwater populations maximum recorded shell width maximum height maximum weight freshwater shells exterior shell basically whitish yellowish net like dark reddish violet pattern pattern variable depending environmental factors partly presenting bands occasionally evenly dark shell variable color color patterns showing great shell coloration patterns plastic species genus qualities influenced factors like composition water type nutrition individuals habitats colleagues showed outer coastal waters baltic_sea nearly black shell form predominant inner sheltered parts coastal waters yellowish green forms prevail observed specimens darker substrate black dark brown shells specimens pattern white drop like spots dark red background specimens spain pattern stripes specimens balkans possible combinations white drop like spots stripes animals habitats dark light bands shell images showing color patterns shells shell shape similar shell shape spherical shape usually descending species display large morphological makes difficult differentiate overall outline shell species identification recent literature coloration patterns shells relied identify specimens characters proper identification shaped light reddish red margin bearing broad rib called ridge inner surface muscle attached rib rib long thin base thin lacking characteristic features visible juveniles sexual border rib shield straight females curved males shape observed specimen france spring near bar montenegro double rib present rib shield reduced specimen rib shield reduced distinguished mentioned species having rib pit formed rib rib shield rib shield consequently rib pit lacking species differs having addition rib absent visible soft parts animal light yellow black head long eyes large black foot whitish like species family type small marginal teeth help brush food particles colleagues species reproductive system separate sexes number males females sex determination system confirmed species females openings located edge mantle mantle cavity opening opening laying eggs accepts sperm connected storing sperm opening laying eggs egg cells originate egg cells travel chamber occur eggs develop capsule formed eggs laid males forming sperm structure examined travels mixes fluid finally goes located inner right following illustrations reproductive system female male organ systems system pressure lower value marine subfamily pressure subfamily belong similar land family ecology habitat prefers lowland habitats switzerland occurs calcium rich waters small inhabits central lower parts rivers deep including water tidal rivers lives lakes bottoms rarely lives springs ground water caves example found living lakes streams rivers ireland species lived water species easily stones allows live fast running waters wave zone lakes ability live freshwater water demonstrates species small live depth coastal waters water populations live baltic_sea baltic_sea black_sea populations water tolerate higher populations freshwater water populations higher accumulation positive substances foot species lives hard benthic typically rocks lives rarely dead wood mild organic pollution low oxygen content tolerate long periods ice lives waters waters serves indicator species river monitoring germany spreading populations high tolerance degraded habitats large found living stones dead wood freshwater environments lives stones marina water baltic_sea species found species found dominant fauna central northern baltic_sea water populations reach lake reach population species found population spring river stable temperature allows continuous reproduction port september density juvenile recorded feeding habits feeds mainly living stones consuming consume green algae poor quality food supply contain green algae cell walls species digest brown small studied effect grazing algae life cycle means individual animal distinctly male female cross occur sex ratio structure unique divided parts eggs usually laid mid april october temperatures eggs laid egg deposited stones shells individuals females usually lay cluster containing single female usually lay summer autumn fresh white older yellow brown bear outer layer diameter water usually smaller sterile small diameter laid number eggs egg capsule changes depending environment eggs capsule freshwater opposed eggs capsule water usually egg develops remaining eggs serving nutrition embryo results single juvenile hatching capsule juveniles shell length hatch days days ash free dry weight newly hatched laid spring hatch months august september late summer development temperatures hatch spring months shell grows mainly august shell growth winter reach sexual maturity year shell length life span years age estimated years mortality rate low summer higher winter ice storms substrate result mechanical damage parasites predators parasites include species serves intermediate host second intermediate host found small small species main host usually infected mantle cavity found mantle cavity species parasitic species found predators include common freshwater fish prey birds
Theodoxus fluviatilis