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Nth Sulawesi - A Night of Crustaceans at "Black Rock"

4th July 2017 and after three fantastic wall dives, including "Mandolin" and "Tanjung Kopi", we decided on a night dive at "Black Rock" situated along the coast toward "Tanjung Pisok". The site has a depth of about 11m with areas of reef and sand providing a habitat for small critters, so I changed the lens on the camera for close-up work and checked the torch batteries.

The intermittent failure of my torch, meant I was often swimming in the dark, or by the light of others, or the light of the moon off the sand, or, when necessary, by the focus light on my strobe.

Despite this small inconvenience it was another great dive and one full of Crusty Critters, with lots of hermit crabs, decorator crabs and various species of shrimp. I have never had so many weird crustacea rock up on a single dive.

Hope you enjoy some of the photos from what turned out to be a surprising 90 minutes on what we may have expected to be a fairly ordinary dive site. I should have known better.

Lisa's Mantis Shrimp (Lysiosquillina lisa)

Jacky found this mantis shrimp and signalled for me to approach it very, very, quietly. So I was was creeping slowly closer to get the shot, trying to breathe so slowly that no air would come out. I managed to get two photos - the one above, and, immediately after, just the hole. Clearly I was not quite enough.

Jacky thought I had missed the shot and was initially a bit disappointed, but personally I don't think I could hope for a much better photo of the mantis shrimp laying in wait for prey at the entrance to its burrow.

These mantis shrimps have long, back folding, sword like appendages that shoot out at high speed to grab passing prey. They hunt from the entrance of their burrow, waiting with articulated eyes that independently search in all directions around their home. Their feelers remain in contact with the edge of their hole to detect any vibrations from approaching predators, or poorly coordinated cameramen like me.

I was photographing a related species of the this mantis shrimp in Lembeh Strait once, a Pink-Eared Mantis (Odontodactylus latirostris). It sat there near a piece of timber, sticking up prone above the bottom, symmetrical and looking like Salvadore Dali, with wild eyes and feelers that looked like a thin Dali moustache sticking out each side. It sat there for a few photographs and then, WHACK, the clubs he has on his front appendages to stun prey, hit the camera port with a resounding bang.

Pink-Eared Mantis Shrimp (Odontodactylus latirostris)

There were also some pretty amazing decorator crabs on this dive and I managed to get some reasonable photos of three of them. One thing I shall have to do is to fit the red filter on my focus light. Light disturbs these crabs at night and focusing was difficult with a combination of low light and movement. I had my D300 set for a point focus, to ensure that I could specifically get the eyes in focus within the small depth of field provided by the lens I had. So it was the frustration of getting a large camera and housing close and then the shutter not releasing when I wanted it to because it could not get a clear enough focus with the lower light level, movement and lack of definition of sponge covered decorator crabs.

Blunt Decorator Crab (Camposcia retusa) covered in a living garden of sponge - recognised by its tear shaped eyes.

Then we came across what now has to be my favourite decorator crab. It (mostly) stayed still, in a good position for a photograph, looking like a proud Japanese samurai in colourful armour. Its recognisable by its black and white legs and spotted claws that protrude below its heavy covering of corallimorphs - its the amazing Corallimorph Decorator Crab - magic.

Corallimorph Decorator crab (Cyclocoeloma tuberculata)

Sitting in an anemone was the small and aptly named (particularly for Indonesia) Orangutan Crab, covered in fine red hair and with brilliant red eyes. If you look carefully at the photos below, you can see, in the first one, a small shrimp sitting between the crab's eyes and, in the second photograph, you can see another small shrimp up in the top left hand corner. The actual scientific name of this interesting little crab seems to be a work in progress. It was formerly classified as Achaeus japonicas but now identified as Oncinopus sp 1. These crabs are also often found on bubble coral.

Orangutan Crab (Oncinopus sp.1) complete with shrimp on its head.

And then came the tumbling hermit crabs, and there were many, large, small and all the sizes in-between. When caught in the torchlight they scuttled and tumbled off for shelter, which made photography a little difficult, until they backed up against a rock or piece of reef and could go no further - for a while.

Anemone Hermit Crab (Dardanus pedunculatus)

This is a left handed hermit crab which carries symbiotic anemones on its shell. When they change shells, its been observed that they carefully move their anemones from the old shell to the new. I have not seen it.

I was happy with this photograph which shows the crabs characteristic green eyes, banded eye stalks, bristles and large left claw.

Hairy Netted Hermit Crab (Aniculus recipes)

Another interesting and colourful character was the aptly named Hairy Netted Hermit Crab with its blue eyes, yellow feelers and mass of hairy legs.

Among all these crabs were many shrimp but I was unable to photograph many of them as they were just too fast in trying to escape the torch light and camera. It was also difficult to get the large ND-30 camera housing into the small areas between corals and reef where these shrimp escaped to shelter. But I got a few.

The prawn photographed below was very good at disappearing quickly and I think I was lucky to get these shots of this beautiful little prawn. It is similar to the Humpback Prawn (Metapenaeopsis lemellata) but I think it may be the Indonesian cousin. It has the habits of all humpback prawns in that it is nocturnal and when disturbed (and I suppose also during the day) it buries itself in the sand with only its eyes sticking out.

I caught a photo of this one on the surface, but he was soon off and buried himself in the sand, a little half heartedly at first, giving me another photograph - but then he disappeared completely. The colour of its eyes is amazing.

Indonesian Humpback Prawn (Metapenaeopsis sp.2) - I think, maybe , perhaps

Indonesian Humpback Prawn - buried in the sand, initially still visible, but after this photo disappeared completely.

Under the ledges and in holes, were the usual Banded Coral Shrimp, usually in pairs, sometimes groups of smaller ones. No matter how many of these you see, they are still amazing to watch. Every now and then you get one in the right position to take a photo. The benefit of these shrimp is that they are not really fast movers and they seem to get used to a photographer or diver being close and looking at them. Maybe this is because because they also often act as cleaner shrimp and need larger creatures to get close, while the shrimp is advertising its cleaning services with its colour and spread claws. They are not at risk of becoming a meal due to the service they provide.

I was able to get a reasonable photo of one of the pair that sharing an overhang. It provided a suitable end to a night of amazing crustacea.

Banded Coral Shrimp (Stenopus hispidus)

I imagine there were a heap of other small crabs, shrimp and prawns that were inhabiting the environment of this dive site - I just missed them. It was not until after the dive that I realised that the site had such a variety and range of crustacea. Next time I dive this site I will focus on finding more of these interesting and colourful invertebrates.

It was great to get some reasonable photographs - but it was, as usual, better just be able to find and observe these amazing creatures.

It was not all crustacea on this site - there was other stuff that was pretty good also. But thats another story, as are the crabs and shrimps from other dive sites in my favourite part of the underwater world - Nth Sulawesi. Magic.

A fish in its night time colours resting under an overhang

Thanks for your interest.


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