New Zealand pea crab
 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.