Reef creatures at night in Mo’orea, French Polynesia

While I was grad student at UCLA, I twice had the opportunity to TA a field course in Mo’orea, a small island next to Tahiti in French Polynesia. These are some photos I snapped on a night dive last time I was there, in the spring 2012. Enjoy!

An anemone hermit crab at night.
From Wikipedia: Dardanus pedunculatus usually lives on coral reefs and in the intertidal zone, at depths of 1–27 metres (3–89 ft). It usually carries sea anemones on its shell, which it uses to protect itself from its main predator, cephalopods of the genus Octopus. The anemones are collected at night, and comprises the crab stroking and tapping the anemone until it loosens its grip on the substrate, at which point it is moved onto the gastropod shell that the hermit crab inhabits.

A parrotfish in its mucus “sleeping bag.”
Many species of parrotfish surround themselves with a mucus bubble at night. It is thought to protect them from predators by keeping their scent out of the water and possibly provide an early warning system if the mucus is broken by an approaching predator. I wasn’t able to identify this particular species, suggestions are welcome.

The chocolate tang Acanthurus pyroferus.
Tang and surgeonfish (family Acanthuridae) have a sharp scalpel-like blade on their caudal peduncle (the part right in front of the tail) that they can whip around to slice a predator.

The banded cleaner shrimp Stenopus hispidus.
Again, from Wikipedia: “Stenopus hispidus lives below the intertidal zone, at depth of up to 210 metres (690 ft),on coral reefs. It is a cleaner shrimp, and advertises to passing fish by slowly waving its long, white antennae. S. hispidus uses its three pairs of claws to remove parasites, fungi and damaged tissue from the fish.”

The urchin Diadema savignyi.
No much to say about this guy, just don’t step on one. The spines are every bit as sharp as they look.

A moray eel. I think the undulated moray Gymnothorax undulatus? 

The ass end of one of the most beautiful fishes I’ve ever seen. Some kind of gurnard?

The spotfin lionfish Pterois antennata, I think.
Also viewed from the posterior. This species has other common names, but who cares?


A Jellyfish’s Offense is a Sea Slug’s Defense

Arms races between predators and their prey have been common in the evolution of life. Gazelles run a little faster to help them escape cheetahs, then of course the cheetahs speed up to keep catching their meals. Bivalves (clams, scallops, etc.)  and snails have evolved some tough and elaborate shells to protect themselves, and in response the crabs, octopuses, and fishes that eat them have developed incredibly strong claws, drills, or teeth to crush, open, or bore into the shells. And of course toxins can be synthesized to ward off all sorts of enemies looking to take a bite out of you (the slow loris is by no means the only animal to do this, but it may be the cutest).

navanax eating

A cephalaspidean sea slug of the genus Navanax devours an aeolid nudibranch slug. Aeolids can sometimes steal stinging cells from their prey, jellyfish and their relatives, as a defense against predators, but that doesn’t seem to have worked in this case.
Image taken from

But what if you’re just slow and squishy? In the case of nudibranch sea slugs, some of them make up for this vulnerability by eating cnidarians (jellyfishes, coral, sea anemones), stealing their stinging cells, and planting them in their own tissues, ready to fire at an unsuspecting predator. The process is called kleptocnidae, and even though it was discovered almost 100 years ago, it’s been the subject of very little study since then.

A while back, I wrote about kleptoplasty. It’s the process whereby sacoglossan sea slugs steal chloroplasts from their algal prey and use them for photosynthesis, essentially turning themselves into solar-powered animals. However, see a recent study calling into question the extent to which the slugs use photosynthesis for survival.

Regardless of exactly how important solar power may or may not be for the survival of sacoglossans, nudibranchs have arguably taken the art of stealing from their prey to a different level. Nudibranchia is the best known group of sea slugs, largely because their patterns are so colorful that they often look more like cartoon characters or art projects than real animals. But we all know beauty doesn’t necessarily make you nice, and nudibranchs could be considered masters of deception in that regard. In contrast to the herbivorous (i.e. vegan) sacoglossans, nudibranchs are voracious predators, devouring sponges, corals, bryozoans, or other sea slugs – some will even cannibalize members of their own species!

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