New Zealand Pea Crab - Ecology

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 endeavour. 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%.