Small and fragile, Porcelain or Anemone crabs inhabit the surface of larger species of sea anemones found on coral reefs. The species which I’ve been able to shoot the most is the cream and pink-spotted Neopetrolisthes maculatus, which I’ve been finding n pairs quite frequently, with one larger and the other smaller (male and female probably but not sure which is which? they have six pairs of legs which I could’ve checked under however it’s abit tedious seeing as they’re only about 2cm in carapace length).
You’ll notice here that only a small part of the subject is in focus, please don’t think it’s because of my amateur photographic skill, but rather taken deliberately to illustrate a point. said point being, they’re pretty tricky to shoot. Although the crabs themselves tend to stay rather still inside the anemone, that doesn’t mean that the anemone wont move instead! Large anemones sway with the flow of water, and this one in particular, situated on a wall about 27 meters deep, contained an allied species of N. maculatus, known as N. alobatus. The difference between the two being mainly in their colour, N. alobatus having black spots on it’s legs and carapace.
Most of the time when I’ve come across these cool little crabs, the anemone that they’re perched on sits in between two large coral heads, or at an awkward angle. this sometimes makes buoyancy control a little bit of an issue if there is a current, and due to their size, getting a large housing us close and personal can be a little difficult at first. Like most aspects of diving, good buoyancy control through proper weighting and regulated breathing can be one of the best skills to have. This is definitely true for taking photos like this, where being aware of your surroundings is key, so as not to damage any sensitive marine life around you.
Keeping neutrally buoyant, usually while upside-down I can imagine is very amusing for these little guys to watch. As I moved in closer, the claws were bared, and the crab began to shift down the anemone, nestling further into its carpet of stinging arms. Porcelain crabs use these stinging arms fro protection from predators such as triggerfish, grouper, octopus, squid and cuttlefish who would make a fast meal of them. when danger isn’t imminent, the Porcelain crab will stretch out it’s mouth parts seen just underneath it’s eyes (they look almost like a secondary pair of arms almost resembling a mantis’) and will fan them out to catch plankton that drift over the anemone.
I find these crabs to be very endearing, and such is the habit of a lot of divers, I sometimes look at them and attribute human qualities to them. I’d like to think of Porcelain crabs as being the bodyguards for clownfish, as the two are usually seen close together sharing the same anemone.