Porcelain crabs have large front claws and huge pincers. Though they look formidable, these appendages are used during territorial fights with similar species, and not for predation.
Though known as porcelain crab, this crustacean is not a true crab. It is a small crab-like animal with a flat, round example of carcinisation, a term used to denote the evolution of a crustacean to a crab-like form from a non-crab-like body. It looks like a crab, and hence, the name. In fact, porcelain crabs are related to squat lobsters. They are a classic form. The porcelain crab is really small with a maximum body width of 0.5 inches.
The flat and compact body enables the animal to hide in between rock crevices and beneath stones. It is also found in between tufts of algae, corals, sponges, and mussels. This organism is commonly seen in rocky shorelines.
Porcelain crabs belong to family Porcellanidae, infraorder Anomura, and order Decapoda. These crustaceans are classified under 30 genera that have around 300 species. They are commonly found in all oceans, except the Arctic and Antarctic. The body color of this crab varies with different species, and may range from blackish-brown to sky blue, green, and white. While some are spotted; mottled or striped species are also common. Given below are some interesting facts about porcelain crabs.
True Crab Vs. Porcelain Crab
The porcelain crabs look like a crabs, but are not true crabs. Unlike true crabs, the porcelain crabs have long antennae. They have three pairs of walking legs, whereas true crabs have four pairs. In porcelain crabs, the fourth pair of legs are too small and are not visible, as they are held against their body. Their tails (or reduced abdomen) are kept folded under their body. When disturbed, they may use this structure as a paddle for swimming up and down.
Porcelain crabs share a mutualistic relationship with many animals. For example, the porcelain anemone crab Neopetrolisthes maculatus is a species that is mostly seen with sea anemones. While the anemone offers shelter and protection to the porcelain crab, the latter keeps the anemone clean. It is said that these organisms compete with clownfish for establishing their territory in sea anemones.
These animals have feathery structures on their mouth parts that look like arms. To be precise, the outermost pair of maxillipeds have fan-like structures. These crustaceans indulge in filter feeding using these feathery extensions. Their diet mainly consists of plankton, which they collect from the water, through sweeping movements of their arms. The mesh-like structure works like a sieve for collecting food.
They use the innermost pair of maxillipeds to gather food particles that are caught on the fine hair and carry them to the mouth. They may also use their claws to scrape debris from substrate and consume it. So, the feeding habits of this organism includes scavenging too. They may also feed on the mucus of sea anemones.
So, the name porcelain crab is derived from the delicate and fragile body of this organism. These crustaceans hide inside rock crevices and beneath stones, whenever they are threatened by predators. If there is no other way to escape, they shed their limbs to divert the attention of predators, and escape. The lost limbs will regenerate after a few molts. Limb autotomy is found to be an effective escape mechanism in these marine animals.
Porcelain crabs are often found as heterosexual pairs that breed throughout the year. It is said that females become sexually mature as they attain a body length of around three to four millimeters. The male deposits sperms inside the female, and the latter carries eggs in a brooding flap located in the abdomen. The eggs are usually reddish-brown in color.
It has been found that female porcelain crabs may carry more than 1,600 eggs at a time. On an average, they carry around 600 eggs. The eggs hatch as free-swimming larvae that feed on plankton. These organisms reproduce rapidly, especially in warm waters
Nowadays, they are popular as pets and are found in reef tanks. Feed them with shrimp or meaty food, or commercial food meant for filter feeders. The pH of the water should be maintained between 8.1 to 8.4, and the temperature must range between 72 to 78°F. The specific gravity must be 1.023 to 1.025, and alkalinity should be between 8 to 12. Though it is easy to take care of porcelain crabs in aquariums, it is better to have a thorough understanding about their requirements.
Porcelain crabs are fascinating marine organisms with amazing features. They are peaceful animals that live around two to three years.