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.
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.
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.
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.
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!
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.
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.
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!
As Phyllodensium Nudibranchs are uncommon, bizarre and attractive at the same time, they always make a good Blog post. Specially when they are found in numbers. Having blogged some weeks ago already about the Solar powered Nudibranch, it’s today the turn of the Kabira Phyllodensium (Phyllodensium kabiranum). As they are very well camouflaged when feeding on Soft Corals, they are very hard to spot – but once you found them, they make a very attractive subject. Specially, when they are isolated from the soft coral, like this one in the picture. At the moment we are finding 5 of them at Nudi Retreat – but we are also seeing them at some other Dive Sites here in Lembeh Strait.
The blue highlights in its brown tentacles make it already very attractive – but when you pass the right moment of the surge moving all it’s cerata to one side, you can see its beautiful orange base. Keep looking within Heteroxenia and Xenia corals and you might find one.
The molluscs is a big and very diverse group consisting of animals as different as a mussel and an octopus! Most colorful and strikingly patterned among the molluscs are the cowries, used as currency in different cultures over time and now prized collector items due to their shining and often brightly coloured and patterned shell. However, what we as divers see, is not the shell itself, but the soft mantle of the animal, wrapped around the shell. The mantle is usually even more beautiful than the shell itself, often bearing a striking similarity to the prey of the cowrie, with tentaclelike protrusions if feeding on coral species. Due to the potent poisons used by cowrie prey as a deterrent to predators, cowries are often adapted to only a single prey species. Thus, being specialists, cowries sometimes has achieved more or less perfect similarities to their prey of choice, making many of them very hard to find, and among the best examples of camouflage.
There are exceptions to this rule though. The first cowrie of the day was found at 30 meters of water in Angel’s Window. It was the very rare tiger cowrie, which with its striking black and yellow probably is very obvious. Interestingly enough, tiger cowrie finds are rare enough that they merit a blog entry in itself, as can be seen if you go to earlier entries in this series. Tiger cowries feed on a genus of sea fans, which seem to occur in the deeper range of “normal” diving, thus maybe explaining the few observations of this cowrie.
The second cowrie was situated just half a meter or so from the tiger cowrie. This was a wire coral cowrie, which also is a cowrie I have never seen before. I would probably rate the looks of the wire coral cowrie even higher than that of the tiger cowrie, but both are decidedly striking animals. BTW, between the two cowries we found two baby clown frogfish, making this square meter or so the hot spot of Lembeh today.
Finally, Paulus and Joni found my absolute favorite cowrie, one of the small ovulids living and feeding on soft corals of the genus Dendronephtya. There are several very similar species, and detailed examinations are needed for exact species determination for some of them. Paulus and Joni found not only one, but two of those tiny, and very well camouflaged animals, once again showing that a great guide with good eyes make a lot of difference on muck dives.
As a teaser for tomorrow’s entry, this nightdive´s tally of cephalopods was two flamboyant cuttlefish, one coconut octopus, two reef squid, one wunderpus and one bobtail squid. And that was in one hour! The last couple of days and nights have included additional sightings of starry night octopus, several (many!!) blue ringed octopus, mototi octopus, broad-club cuttlefish, pygmy cuttlefish, long-armed octopus, mimic octopus and reef octopus. So, if nothing else steals the headlines, the subject for tomorrow will be the smart invertebrates, the octopus and their closest relatives.
On yesterdays afternoon dive we went out to see Harlequin Shrimps (and we also found several ones). But before looking for Harlequins in the shallows i spend some time around some Bommies a little bit off the dive side. I took my time scanning the Ascidian Clusters for cool Micro Critters like Nudibranchs, Flatworms or Shrimps. This is when i found this little guy in between the tiny soft corals and Xenia Corals of a Ascidian Patch. Please note the beautiful stripe pattern and the little patch of red dots on the bent part of his back. I don’t know how it’s called, but i think it is a very beautiful shrimp.
Before i even start with this post: Thank you to everbody crazy enough about diving to read our BLOG on Christmas day. We hope you all have a good time where ever you are – even if there is no Muck diving around.
But back to the post: Of course we don’t have snow here in Lembeh and also no real Christmas Trees. But North Sulawesi is still a strongly Christian region and Christmas is very very important to the people here. So even if you don’t want: these days you hear Christmas songs all the time. Having these melodies constantly in my head since a month (or more) i knew straight away that i found the perfect shot for my Christmas BLOG Post when i saw this goby sitting on the cover of a old generator on NAD Housereef. As if he knew it, he posed exactly on the one spot, where you could still read the print that says “silent”.
And actually: Here at NAD Lembeh it is really gonna be a “Silent Night” as most divers checked out yesterday. We only have 3 guest left and are getting full again from tomorrow on. So we whish everyone a “Merry Christmas” and say good bye with a little Christmas present for all our BLOG readers: A picture of a Soft Coral Shrimp – such a beautiful shrimp … found at Pante Parigi by our Guide Joni.
Now Simon managed to download his photos, we have a few (not many due to strobe batteries not being used for several months) photos from East-Lembeh. The Sites were lovely as mentioned in the previous post, and the topography was fantastic. There can be current, but that can’t be helped when diving in exposed areas.
These trips are dependant on weather, and as such if interested you should enquire beforehand, but we cant give a definite answer until a few days before!
The trip involves 2 dives on the Eastern Side of Lembeh, lunch on the beach / boat, then one dive in the south on the way back around to the Straits.
It is great Wide angle diving, but you can also get some good macro/telephoto shots of nudibranchs and Anthias.