User:Jessica87nz/sandbox

The New Zealand pea crab, Pinnotheres novaezelandiae, is a small, parasitic crab that lives most commonly inside New Zealand green-lipped mussels. Adult females are about the size and shape of a pea, while adult males are smaller and flatter. Adult New Zealand pea crabs are completely reliant on their host mussel for shelter and food, which it steals from the mussel's gills. The New Zealand pea crab is found throughout New Zealand and can infect up to 70% of natural populations. These crabs are of concern to green-lipped mussel aquaculture because they reduce the size and growth of mussels, although infected mussels can be harvest and consumed.

Description
Adult female New Zealand pea crabs have a soft-shelled exoskeleton. Their carapace is oval in shape, ranging in size from 9.3 to 20.2mm wide. Sexually mature adult females almost always have eggs that are tucked under their abdomens, giving them a more spherical appearance. Adult females are opaque white in color. Developing eggs change color from red to orange to yellow before they hatch, giving the brooding mother a different tint at each stage Adult male New Zealand pea crabs have a hard, chitinous exoskeleton. Their carapace is smaller and more dorso-ventrally flattened than that of the female, ranging in size from 3.2 to 11.8mm wide. Adult males are a creamy white color with distinctive orange markings.

Ecology
Female New Zealand pea crabs spend their entire adult lives within a single host. Adult males will only leave their host in order to find a mate. The hard exoskeleton and flattened body shape of the male New Zealand pea crab helps with this endeavor. New Zealand pea crabs are completely reliant on their host for food, shelter and a place to mate. The New Zealand pea crab collects food by sitting on the gills of the green-lipped mussel and stealing food strands from the mussel. The relationship between the New Zealand pea crab and the green-lipped mussel is one of parasitism because the crab damages the mussel's gills when taking food. Infected mussels are also smaller and slower growing than uninfected mussels.

The New Zealand pea crab is endemic to New Zealand and is common throughout the country, inhabiting the North Island, South Island, Stewart Island and the Chatham Islands. The New Zealand pea crab lives most commonly in green-lipped mussels (Perna canaliculus), but can also be found in many other bivalve molluscs including the blue mussel (Mytilus edulis aoteanus), the Pacific oyster (Crassostrea gigas) and a species of clam (Chione stutchburyi). The infection rate in wild green-lipped mussel populations can range from 0 to 70%.

Edibility
Pea crabs are edible and were once a delicacy in the USA. George Washington used to love having pea crabs floating in his oyster soup. Mussels infected by pea crabs are also edible.