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!

TK delivers!

Whenever you visit the same dive area several times, some dive sites seem to consistently deliver more than others, and, correspondingly, some less than you would wish. Here in Lembeh my favorites are the Aer Bajo sites and Hairball, where many uneventful starts of dives have been turned around to glorious experiences. The different TK sites on the other hand have for some reason not really caught my interest that much, despite that if I really think hard I actually have seen some really neat animals there. My expectations for yesterday´s morning dives were less than stellar, as the first dive was in Nudi retreat (coral dive, why??) and TK 3. Nudi retreat delivered a couple of cool Xeno crabs as well as a beautiful soft coral crab, which was fine, and perfectly OK. Happy with that. TK on the other hand, in the words of a well known dive resort owner,  just kicked the balls out of any kind of negative feeling about that site.

Paulus, my dive guide for the day, first found a weird flat crab buried into the rope sponges that are so common in TK (pictures coming in a later blog).  Just after that a great Janolus nudibranch posed nicely,

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followed by a number of “commoner” nudis, and a beautifully colored devilfish, showing of its pectoral fins.

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A couple of minutes later in a small patch of rope sponges and debris, two beautiful frogfish and one common sea horse were found.

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That was just the start. After that, less than 5 meters apart, a flamboyant cuttlefish was hunting,

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a hairy frogfish came walking by, and, finally,

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a coconut octopus did his (or her) amazing show with a couple of beautiful shells, hiding, digging, watching me and walking around with the shells.

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So, TK, I am officially sorry for my negative attitude. TK after this climbs significant steps on my favorite dive site list. Simultaneously, my wow for this trip of concentrating the photo shooting to a few of the best subjects on each dive, was blown to pieces. But what can you do, this was like letting kids loose in a candy store, Danes loose in a beer pub, Djengis Khan loose in a village of pacifists or Simon loose in a camera store!

Why good things can be bad.

In every documentary I have seen and book I have read about Lembeh, it is stated that the waters of Lembeh are exceptionally productive partly due to the currents that bring nutritious water through Lembeh strait regularly, partly due the black lava sand more or less defining Lembeh that leaks nutrients into the water. It is easy to envision that such an environment with loads of biological production would be very nice to live in for the creatures inhabiting the strait.

Wire coral gobies, feeding on plantkon that is swept through the strait by currents

Wire coral gobies, feeding on plantkon that is swept through the strait by currents

Surprisingly enough, evolution seems to have been working overtime  in Lembeh, partly shaping the foraging skills of the animals here, but even more obviously perfecting their skills of evading predators. Why is the pressure on prey animals tougher here in the seemingly benign waters of the strait than in other less productive environments?

Lizard fish with the elongated fin rays of a former sand diver in Lembeh

Lizard fish with the elongated fin rays of a former sand diver

Mathematical models of predator and prey populations give us the answer.  For every population there will be a maximum number of individuals that the environment can provide for. This number is called the carrying capacity of a population. If one increases the carrying capacity for a prey population, the prey population will increase the number of offspring that is produced. However, if there are predators around, predators will take advantage of the increase in the reproduction of the prey population, and the predators will increase their population size, leaving the prey at a low but very productive density. Thus every prey individual alive will be faced with a much higher risk of being killed by a predator than in a less productive environment, setting the scene for evolution to try out more and more bizarre and elaborate ways for the prey to survive the onslaught of the predators. Obviously there will be competition between prey on being safer than anyone else which will feed evolution with a drive to use whatever genetic variance giving anyone an advantage over conspecifics or individuals of other species.

Soft coral crab with an almost unbelievable camouflage on its soft coral host in Lembeh

Soft coral crab with an almost unbelievable camouflage on its soft coral host

Why stay here then? Is there really anything good at all living in productive environments then given that you as prey face a never-ending threat from predators? Well, it turns out that the alternative is just as bad. In prey populations that are controlled by food availability rather than predators, prey will reach densities where the food resources are heavily used and most everyone is on the verge of starving to death. The sad truth about being an animal in nature is that, with very few exceptions, you either live a life where every day is a constant struggle to make ends meet, feeding on the very scarce resources not already being utilized by someone else, or you live in constant fear of being torn in pieces by something bigger and fiercer than you are! Sucks, doesn´t it!

Shrimp seeking refuge in anemone

Shrimp seeking refuge in anemone

Luckily for me, as I really enjoy exquisite examples of prey adaptations to evade predators, many prey animals in Lembeh will be on the “lots of food around, but holy smoke it is scary here”  end of the scale. Every dive here will give even a first time diver in the area many examples of what living in such an environment does to prey animals. Also, as a nice side effect, the strait is littered with predators, which we will get back to in a later blog.

Back again

Back again!

After leaving Lembeh in October I honestly thought that it would be about a year until I could visit again. I had quite a number of trips elsewhere planned and also a lot of stuff to do on my day job. After spending the rest of the fall with doing paperwork, and an extremely early winter onset at my home in Sweden, combined with a record amount of snow, it became clear that I had to get some diving in before planned. So here I am back in Lembeh again, more than happy to be blogging about the stuff we see and take pictures of during the next couple of weeks.  I know I am most likely preaching to the choir here, but it was pretty obvious already yesterday five minutes after my arrival that 28 degrees Celcius and sun so strong that you actually would benefit from sunglasses beats the climate around the polar circle by just an incredible amount on the life quality scale.

Wire coral shrimp in Lembeh

Wire coral shrimp

What are the differences then from October? Well, some are resort based. Simon and his staff have fixed a really nice bar on the second floor with a great view over the strait. The boats were already fixed in October, but now there are new, quick and very well planned boats here. The guides are the same, which I am very happy with. The former chairs, which probably were made of concrete, iron scraps and lead, have been replaced (some would say that that is a bad thing, breaking a long tradition, but then again other people seem to want to be able to actually move their chairs). Compared to my last visit, being the low season now, there are very few people here. Having visited Lembeh during more or less during all seasons, I really wonder why there is a low season, as the diving has been very good whenever I have ben here.

Wire coral shrimp in Lembeh

Wire coral shrimp

The diving is not the same though, different animals seem to be common at different times. And that takes us to the differences under water.  Most of the seasonal differences here seem more to be a question of differences in densities of animals rather than differences in what species can be found here. The flamboyant cuttlefish, which were common to the point of being not very interesting in October, have left their marks with eggs in most of the empty coconuts on the sands.

Flamboyant cuttlefish egg

Flamboyant cuttlefish egg

Flamboyants are still around, but not as many as then, which makes sense, as flamboyant and their relatives die soon after mating. The same goes for blue rings that are tending their eggs now, but are not seen in the same more or less ridiculous densities as in October. I would be surprised if there are as many frogfish around as on my last visit. But, that said, I am pretty sure that something else will be much more common now. Apparently there are quite a number of Harlequin shrimp here now, and they are always fun to watch.

Harlequin shrimp in Lembeh

Harlequin shrimp

After some days of diving here, I will get back to you with what else is common now. Wire coral shrimps were very common today at least, as you can see from today`s shots!

Wire coral shrimp in Lembeh

Wire coral shrimp

Spot The Difference

These two Shrimpgobies are very similar, and if you aren’t paying much attention you will dismiss them as being the same.

These are two of my favourite critters, and i consider them a connoisseur’s choice when people make their wishlist for Lembeh.  They are very hard to shoot until you hit Zen mode and all the wildlife starts ignoring you, add to that once you scare them you have to wait 5 minutes minimum for them to come out of their hole again – it can eat up your divetime quite quickly.

The big give away between the two is the dorsal fin, and you will also notice that thier behaviour is a little different – the Yellownose has a cool way of displaying to show it’s territory.

Yellownose Shrimp Goby

Yellownose Shrimp Goby

Black-Ray Shrimpgoby

Black-Ray Shrimpgoby

 

Little Green Hairy Shrimp Video

Little Green Shrimp

Little Green Shrimp

I did one dive on New Years Day, and I found this little guy:

This shrimp was first found by one of my guides in 2011, and amazingly enough it has evaded me until yesterday.  Every-time I have dropped in on a site where they had a confirmed sighting, it has moved.  Or one time the guides found it when I was on a dive, I had a deco stop and it was too deep :(.

As far as I am aware, this has completed everything i could see here in Lembeh, now I just need to see them all again and get better photos!

A special thanks to our dive-team, I can say without doubt that they are the best in the area.  As a team they all help each other and they all have different strengths which complement each other.

Anyway, here is the video, hopefully see you sometime in 2013:

Categories: Creature Feature Tags: , , ,

Favourite Photos of 2012

Well it’s the year end, so i thought i would post my favourite 12 photos of the year.

The problem is I dont have any from before 25 September 2012, which was when i (finally) started diving in 2012!

Hopefully for 2013, i will be able to post a favourite photo from each month.

A special thanks to Bent for making me get back in the water again, and to Mood and Serge for keeping me going, and of course Bill for selling me a whole load of equipment for my 5Dmk3!

Happy New Year to you all.

Simon, Zee, and Bella and the team at NAD