Precociously developed Ascarophis sp. [Nematoda, Spirurata] and Hemiurus levinseni [Digenea, Hemiuridae] in their crustacean intermediate hosts

Two adult and one subadult (L₅) Ascarophis sp. were recovered from amphipods Gammarus spp. sampled in Métis Bay, Quebec. Sexually mature metacercariae of Hemiurus levinseni were found in the mysids Neomysis americana and Mysis stenolepis collected from St. George’s and St. Ann’s Bay, Nova Scotia. Both of these helminths are normally parasites of fish as adults. Precocious development may result in either the acceleration of gamete production in an intermediate host or a shortened life cycle where the usual obligatory vertebrate host is no longer required.