Life cycle of Coitocaecum anaspidis Hickman, a New Zealand digenetic trematode

Abstract

The life cycle of Coitocaecum anaspidis involves three important stages. The adult occurs in Galaxias brevipennis, G. attentuatus, Gobiomorphus gobioides, and in specimens of Anguilla spp. less than 30 cm. long. Potamopyrgus antipodum and P. badia are the molluscan hosts of the sporocyst and cercaria. In New Zealand the cercaria attacks and encysts in Paracalliope fluviatilis, and in Australia in Anaspides tasmaniae. A metamorphosis of the cercarial larva into a progenetic metacercaria takes place in the amphipod.Paracalliope does not become infected with Coitocaecum till the crustacean has reached 2·0 mm. in length. The thigmotropism of the Paracalliope fits exactly with the ground-living habit of the stumpy-tailed cercaria. The small river fish feeding in slack water acquire Coitocaecum from Paracalliope.