Care
Porcelain Crabs are smalldecapod crustaceans from the vast family Porcellanidae, which encompasses some30 different genera and over 400 species. Some (such as
Neopetrolisthes spp.) live in host anemones, whereas others (forexample,
Petrolisthes spp.) preferrocky crevices, and there are even some species (e.g.
Porcellana sayana) which live commensally within the shellsinhabited by large hermit crabs. All Porcelain Crabs are filter feeders andrequire a constant supply of planktonic foodstuffs, which they sieve from thewater column by means of their fan-like mouthparts. Those species which live ina symbiotic relationship with large anemones benefit from its protection,whilst the anemone itself is kept clean of particulate matter by the crab (someexperts believe they also eat mucus from the anemone). These crabs are notusually tolerated by clownfish which might decide to reside in the anemone andso are usually driven off. For this reason, if you have an anemone and wish tohouse an anemone-dwelling species of Porcelain Crab, it is best not to keepclownfish in the same aquarium. The exception would be if you were blessed withan XXL tank that has more than one anemone host to offer these critters. Thosereclusive species that do not live on anemones tend to be slower in theirmovements and are generally nocturnal. As they are not afforded protection by ahost anemone, they have evolved a rather startling defence mechanism to deterpredators: that of backing away and dropping one or both of their large front chelae(claws) - which continue to move - in order to occupy the attention of thepredator whilst the crab scuttles away to safety. Such defence mechanisms areknown as autotomy. The chelae are often of such a size, that they are largerthan the rest of the crab; they are never used for catching food but are occasionallyemployed during territorial scraps, and more often simply for keeping a spaceclear in front of the mouthparts to facilitate efficient filter feeding. Anylost appendages will grow back over the course of several moults. These speciesrequire a good amount of rockwork in the aquarium, providing plenty of small,shady nooks and crannies for the crab to rest and scavenge amongst. In smalleraquaria it would be best to maintain a single specimen unless a compatible paircan be obtained from your supplier. In larger quarters, multiple specimens maybe kept together as long as there is adequate hiding places amongst therockwork so that the crabs are not in constant competition with one another forshelters. All species require a mature set-up with areas of current passingover their resting places in order for them to sit safely whilst filtering foodfrom the water. They do this by waving their mouth appendages (the thirdmaxillipeds) through the water, sometimes in quite a maniacal fashion. Theseappendages are oversized with very long setae (hairs) and form a net typeconstruction in order to catch food particles as they float past. PorcelainCrabs require peaceful tankmates and should not be kept with large, aggressive,carnivorous fishes. We recommend that when you first introduce your PorcelainCrab/s, you do so with the aquarium lights turned off, so that the crab/s havea chance to find a protected spot when the fish cannot get to them. Once the crab/shave found a suitable position, it is less likely that they will become fishprey. It may be of interest to note that Porcelain Crabs are not true crabs butactually close relatives of squat lobsters. The process by which thesecreatures have evolved to resemble a true crab is known as carcinisation.Porcelain Crabs may be distinguished from the true crabs by the number ofwalking legs (3 pairs instead of 4, the fourth pair being much reduced and heldagainst the carapace) and the long antennae that originate from the front, toeither side of the eyestalks. Many Porcelain Crab species have dramaticallycoloured exoskeletons, and textures ranging from smooth, mottled, or hairy.
Feeding
All Porcelain Crabs are filterfeeders and require an ongoing supply of plankton and other particulate matter.Some (but not all) will also scavenge meaty aquarium foods. Copepods and babybrineshrimp are very popular with many species.
Breeding
In the wild, Porcelain Crabsare often found together in heterosexual pairs. They use the internal method offertilization, the male passing a tiny sperm packet (spermatophore) to thefemale. The eggs (numbering up to 200) are carried by the female in anabdominal brood flap for several months whilst they develop. Hatching typicallyoccurs during the early evening at full moon. The zoeal larvae have very longdorsal and rostral spines and are planktonic for several weeks before settling.Interestingly, Porcelain Crab larval settlement seems to require (as yet unknown) cues from conspecific adults, as the larvae do not readily settle out of the planktonic stage unless an adult is present.
