Ascarophis sp. (Nematoda: Spirurida) attaining sexual maturity inGammarus spp. (Crustacea)

Ascarophis sp., including sexually mature adult worms, was commonly recorded in the amphipodGammarus oceanicus Segerstrle in the northern Baltic Sea and also inGammarus sp. in estuarine localities in the New Brunswick region of the north-western Atlantic. Species of the genusAscarophis van Beneden (Nematoda: Cystidicolidae) are known as parasites of marine and brackish water fishes, whereas generally only larval forms have been reported from crustaceans. Adults as well as larval stages are described (LM and SEM) and the infection dynamics is analysed in relation to the amphipod population. The results suggest a direct transmission of embryonated eggs to new amphipods, although this remains to be verified experimentally.