Posts Tagged ‘Dive’

A crab up your butt!

All divers interested in critters sooner or later will get interested in crustaceans. Some of the crustaceans are considered “must see” items, such as harlequin shrimp, tiger shrimp, several of the extremely small shrimp recently found here in Lembeh, emperor shrimp and a host of other shrimp. The keyword here is shrimp.  Crabs on the other hand seldom elicit the same interest from divers. However, many crabs have at least as interesting life styles as shrimp, and many are also colorful and attractive, such as the amazing xeno crabs.

Xeno crab

Xeno crab

As those of you that have read my earlier posts might already understand, one of the aspects I find the most interesting when diving is the close symbiotic relationship between many marine animals, where one animal provides another animal with living quarters. Most crabs are free living and do not show symbiotic relationships to other animals. In contrast, here in Lembeh some really fascinating examples of symbiosis between crabs and other animals can be studied.

First of all, unknown to me until my last visit, there is a crab that quite violently excavates a hole into a soft coral and then lives there. It doesn´t seem to matter much what kind of a soft coral it is. This crab is extraordinarily hard to find, as it most of the time is totally buried into the coral. It comes in a couple of color varieties, which seems to some extent be related to which host they inhabit. This of course indicates that the crab sometimes will be outside its hole and walking around on the coral, using the color to blend in, but despite looking a lot for the crab I have never found it outside its lair.

Soft coral burrowing crab

Soft coral burrowing crab

The second crab on my list does a similar, but less violent, excavation into the rope sponges littering the sea floor in dive sites such as TK. This crab does not disappear into the sponge but at least during daytime it clings to the sponge, fitting into the excavation it has dug so tightly that ii is nearly indistinguishable from the sponge.

Sponge excavating crab

Sponge excavating crab

Third on my list, and a crab that I always look for but very rarely find, is the Xenia crab (not to be confused with the Xeno crab). This crab lives its life in between the polyps of some of the species of the pulsating Xenias soft corals.

Xenia soft coral crab

Xenia soft coral crab

Fourth are the swimming crabs living their whole life on a sea cucumber. These crabs are very flat, and have hooks on their legs. They use these hooks to attach their legs to the skin of the sea cucumber, and with the help of their claws they are able to pull the skin of the sea cucumber partly over them selves, thus being very hard to find for a predator. When they get tired of life on the outside of the sea cucumber, they actually hide themselves inside the ass of the host. Next time you see a sea cucumber, take a look up its butt. There just might be a crab looking out on you from the inside!

Sea cucumber crab

Sea cucumber crab

Fifth, and probably the most beautiful of the symbiotic crabs, are the soft coral crabs, or candy crabs as they are known as. These tiny crabs have small hooks on their exoskeleton where pieces of their host Dendronephtyid soft coral will be attached. The crab will also color match itself to the coral, so finding those crabs are best left to an experienced guide.

Soft coral crab on soft coral in Lembeh

Soft coral crab on soft coral

Finally, and maybe in many ways the weirdest and most special of the crabs here in Lembeh, are the Xeno crabs. These crabs live their whole life on a single wire coral, where they attach polyps from the wire coral to their exoskeleton, thus decreasing the risk that any fish will pick them of the wire coral.

Xeno crab on wire coral in Lembeh

Xeno crab on wire coral

Interestingly enough, very little is known about the details of any of the symbiotic relationships I have described here. Without doubt there is a career for a PhD-student interested in cool crab life styles waiting to be done. It is quite evident that some of the crabs incur a cost for their hosts, but it could also be that the hosts in some way has a benefit from its lodger. The quantification of costs and benefits for those relationships is probably quite hard to do, but wouldn’t it be the dream job of all!

Deadliest snakes in the world?

I posted the following picture of a yellow lipped sea krait, Laticauda colubrina, on a couple of web sites after my last visit in Lembeh.

Yellow lipped sea krait

Among comments, several was so sure of the extreme danger I was subject to while taking the picture that they felt it worthwhile to actually write and advice me not to get that close to such a deadly creature, or the second most deadly snake in the world as one comment described it. That is of course very considerate, and I appreciate that to me unknown people actually worry about my well being, but in this case it is not really warranted. In my day job I sometimes handle snakes, and while I am pretty careful handling most terrestrial venomous snakes such as pit vipers, I am pretty relaxed about the underwater snakes, or at least sea kraits.

Wagler´s pit viper. While rarely deadly, it is seriously problematic to be bitten by. Picture not from Lembeh

That said, most marine snakes have extremely potent venom. So am I an idiot without any consideration of danger (think James Bond meets Chuck Norris), or is there more to the risk of being close to a snake than just the potency of the venom per se?

Yellow lipped krait

Well, first of all, humans are extremely bad at doing rational risk evaluations. One relevant example in the context of diving is of course the risk of being killed by a shark, which is many orders of magnitude less than other risks, such as the risk of being killed in a traffic accident, we accept daily. Even toasters are on a global level far more dangerous than sharks, but I have yet to meet a person that questions my sanity when I put toast in a toaster. Not so when I give talks on marine ecology, when I show pictures with sharks, the audience more or less always are pretty certain that a miracle saved me from being torn to pieces by the shark, even if it is a picture of white tip reef shark, being below hamsters or rats on my list of dangerous creatures!

Yellow lipped krait

Still there is the issue of the potency of the marine snake venom? How should that enter into a rational risk evaluation? The risk of actually being hurt, or even dying, of a particular snake´s bite is the product of a number of factors. Included in those factors are the risk of meeting the snake, risk of being bitten once having met the snake, risk of the bite actually penetrating the skin, the risk of being envenomed once being penetrated by the fangs, the amount of venom being transferred once being envenomed, the potency of the venom and the size and health status of the person being bit. So how does the banded sea kraits, such as the yellow lipped krait pictured here, score on such a calculation.

Yellow lipped krait

The risk of meeting the yellow lipped sea krait (or chance, from my perspective) is quite high. I see them approximately every 25th dive in Southeast Asia, so if one does a fair amount of diving, one will definitely run into the snakes. The risk of being bitten once having met the snake is extraordinarily low on the other hand. The only information I have on bites by the sea kraits is that fishermen entangling the snakes from nets have sometimes been bitten. Also there is some anecdotal evidence that the snakes can be aggressive if they feel that their way to the surface is blocked (they breathe air as all other snakes). Sea kraits have rather small teeth, so given that most divers wear wet suits, a bite would rarely if ever penetrate the suit. I have no specific information on the rate of   envenomation once being penetrated, but many snakes do not use their costly venom very often in defensive actions. Also, given that venom is transferred, there seems to be quite some variation in the amount injected.

Yellow lipped krait

The potency of the venom in general, however, is very high for sea snakes. Finally, I am big and quite healthy. So, in conclusion, for yours truly, the combined risk of being killed by a banded sea krait seems to be quite low. Of course your calculation might differ markedly, so do not take this blogg entry as anything else than an example of my very own way of accounting for risk.

Yellow lipped sea snake

It should also be emphasised that there are many other sea snakes that scores much higher on the aggressiveness and tooth size factor above. At least one of those looks very much as the banded krait, so mistakes in identification can be made even by very experienced herpetologists. So even if the kraits are very docile, it might overall be good advice for most people to be a little bit careful around sea snakes.

Yellowlipped sea krait

Categories: Bent's Blog Tags: , , ,

Clingfish on Algae


Nightdiving Nudi Falls

It’s not a secret but it can’t be said often enough: Night Dives at Nudi Falls are just fantastic! Just as yesterday, when we went there with 3 Guests and 2 Guides. We saw loads of different crustaceans, slugs, flatworms, nudibranchs, Squids, Cuttlefish and of course also fishes. For exemple 2 big Tigershrimps with black-blue eyes (normally the eyes are rather orange), a very uncommon Janolus Nudibranch, several species of cuttlefish (Crinoid Cuttlefish, Banda Cuttlefish, Broadclub Cuttlefish), Bobtail Squids, Reef Squid, Soft Coral Cowries and so many other things, that it is impossible to remember them all.

About Nudi Falls: Nudi Falls in a Dive Site in the middle of the Lembeh Strait that is located on the mainland side. It is a combination of  a wall, rocky coral areas, sand, rubble and a beautiful rubble / soft coral field. It is always a good dive – it just has to be timed well with the current. Critters that can be found at Nudi Falls: Blue Ringed Octopus, Wonderpus, Hairy Octopus, Shaggy Octopus, Flamboyant Cuttlefish, various other Cuttlefishes, Pygmy Seahorse (Bargibanti / Pontohi), Seahorse, various Ghostpipe Fishes, Frogfish, Pegasus, Lembeh Seadragon, millions of Nudibranchs, Flatworms, Cowries and crustaceans, Tiger Shrimps, Harlequin Shrimps, many Gobies and and and. It is a definite MUST DIVE, when you come to Lembeh – specially at Night.


NAD Night Safari in 02/2012

Porcelain crab on Seapen / Night dive in lembeh Strait

Lembeh offers not only excellent Muck Diving the whole day long – the night dives are actually the most spectacular ones. And they are versatile: Coral, Rubble or Muckdive … there are lot’s of different styles of Night diving to experience here in Lembeh Strait. With so many critters to see – either things you don’t get to see in the daytime or things that are easier to take pictures of at night. Crustaceans, nudibranchs, cephalopods, fishes, and other weird creatures in the sand, in sponges, in coral, in seapens, in anemones or just floating in the water column. So actually people often not even have enough nights here in Lembeh to experience all the different Night dive sites …

That’s why we are repeating our “NAD Lembeh Night Safari”: One week of diving only when it is dark – with 3 dives every Night. This event will take place in February 2012 and some few spots are still available.

Orange Bobtail Squid in Sarena Besar / Lembeh Strait

18th Arrival Day: 6pm Night Dive19th Transition Day. 3pm Afternoon Dive, 5pm Dusk Dive, Dinner, 10pm Night Dive
24th Transition Day: 11am Day Dive.
25th Departure Day: Departure or continuation on a different package.

Total Dives included: 17


Dives will be conducted throughout the Lembeh Straits, on both Black Sand sites and Coral Sites because we are doing twin tank Night Dives in the middle of the night we will go further and explore the less (night) dived areas – where it will be VERY unlikely to meet other divers!

How and How much:

Book directly with NAD at


Safe Housereef Diving at NAD Lembeh Resort




October was good – Thanks for a great month!





