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!
On a recent dive our Dive Guide Paulus found this beautiful Tiger Cowrie (Crenavolva tigris) on a red seafan, which it feeds on. This Yellow-Black patterned Cowrie is a real beauty and well deserves the name tiger cowrie, which is also commonly used for the much bigger but also much less attractive and less rare Cypraea tigris. Anyway … well spotted Paulus! We hope it will stay on its seafan for a while.
On a recent dive trip to Teluk Kembahu (TK) our Guide Indra showed me this weird shrimp. He was actually trying to find a Bumblebee Shrimp by looking under a pile of old ropes, that were encrusted with a big plastic tarp. But instead he found a big colony of various shrimps including Brittle Star Snapping Shrimps, Big Snapping Shrimps, Rough Tail Sponge Shrimp, Tiger Shrimp and this weird Shrimp. It is a Snapping Shrimp of the Genus Athanas and we found it to be living not on Brittlestars but with a small sea cucumber. There were about 4 or 5 of them. Even though it was not a bumblebee … still a very nice find – specially as i have never photographed this shrimp before.
On yesterday’s second morning dive our guide Stenly found (amongst other things) this little baby Octopus for his three Japanese guests. The little fellow had the size of a fingernail or a small coin and was still transparent … you could even see his internal organs working. Its colouration was a little bit like a pygmy squid or a bobtail squid. We think it is a newly hatched Coconut Octopus – this would also explain his preference for little objects and shells … it was grabbing anithing it could find in the sand and tried to hide in it. This picture shows two little shells that i offered him as a little present.
Some Critters can be seen at daytime but others only at night – like for example the Bubble Shells: They are burried in the Sand during the day and come out at night. But this Wavy Lined Bubble Shell (Micromelo undata) must have been doing overtimes … our guide Paulus found it on yesterdays’s morning dive at Nudi Retreat out on the sand. Even seen at night, Bubble Shells are not very common, but finding one in the daytime is rather special. A cool find for our guests Tyra and Dustin that finished one week of diving with Paulus as their private guide. Have a safe flight home guys and see you again next year!
The Little Green Shrimp (the newly discovered green Phycocaris species) is one of the very hot Critters in the Lembeh Strait at the moment. Several other dive centers already managed to find them and it is becoming a very popular subject with UW (Super-)Macro Photographers – especially with the ones that already have seen ‘everything.’ Even though we have already written several times about the little green shrimp, we now want to officially tell the story about its discovery.
It was first seen in October 2011 by our Dive Guide “Aso”. Aso has been with NAD Lembeh for several years, starting as a gardener and working his way up. Aso has a lot of talent and a big passion for the really tiny stuff. Hairy Shrimps, Tiny Nudibranchs, Lembeh Seadragons and all other critters that normal people almost can’t see are his absolute favourite. So obviously he has his nose always close to the reef – like on that one day in October.
Aso was diving with a group of 4 Divers from Taiwan (Nikki, Color, Ariel & Tommy). They had a great week with superb critters like Hairy Octopus and other really rare stuff. On one morning dive at Dante’s Wall on the northern end of the Strait Aso then saw the Little Green Shrimp for the first time. It looks exactly like a “Hairy Shrimp” … only that it is fatter, has no hair and is green. Luckily Aso’s divers all had cameras and brought back some pictures of the shrimp. Back in the resort, Aso came immediately into the office and said that he found a new species. So we all had a look at the pictures and none of us – even not the oldest guides – knew that shrimp. We then posted the pictures on web forums and it did not lead to any positive ID. The opposite was the case: We got contacted by scientists and shrimp specialists who were interested in samples (We didn’t collect any ). They were not sure if it is a variation of phycocaris simulans (Hairy Shrimp) or a new species of phycocaris. So we started to get really excited about our little green shrimp. Strangely enough, one of our former guides, Jhoe, also found one during a liveaboard charter about a week later – in Alor, which is quite far away from here.
After this first specimen that we saw at the far northern end of the Lembeh Strait we found the Green Shrimp on several other dive sites all over the strait. They are very small (smaller than a grain of rice) but is is still possible to find them, when you know where to look. They live in the Ascidian Clusters in between the little green-white ascidians that look like Olives. And usually we find them in between 10 and 20 meters.
As there are now already several other dive centers finding this shrimp and everyone starts to use its own name for it, we want to suggest “Phycocaris tadetei” (Aso’s real name is Olbert Tadete) as a future scientific name. For day-to-day use, we will stick to “Little green Shrimp” 😉
Nudi Falls is one of the dive sites in Lembeh Strait that you can dive over and over again – at night, in the morning, for the second morning dive or for the first one. And it is always nice. Some of our guests requested to go to Nudi Falls again so that’s why we went back there yesterday morning for the first dive. The critters were all there and we saw countless different nudibranchs and shrimps (including some nice Hairy Shrimps). But the most beautiful thing if diving there first thing in the morning is that there can be very beautiful sunrays in the shallows – specially when the visibility is as good as it was yesterday. This picture is taken in 4 meters of water right under the boat. Thanks to our Dive Guide Joni for posing for this picture …