Echinogammarus lusitanicus (Amphipoda), a New Intermediate Host of Echinorhynchus truttae (Acanthocephala: Echinorhynchidae).

Abstract

The infection of brown trout (Salmo trutta) by the acanthocephalan parasite Echinorhynchus truttae is initiated by the ingestion of gammarid crustaceans harbouring the cystacanth form. Gammarus pulex has been reported as the common intermediate host of this parasite species. The absence of G. pulex in the rivers of Spain suggests that native gammarid species may play the role of intermediate host for E. truttae, which is the only acanthocephalan species reported in salmonids in this country. The aim of the present study was to investigate whether native gammarid species of Galician rivers can act as intermediate hosts of E. truttae. A total of 263 gammarid specimens were collected from rivers in Galicia and fixed in 70% ethanol. They were examined under stereomicroscope for the presence of acanthocephalan larval stages. In one gammarid specimen identified as Echinogammarus lusitanicus, one cystacanth of Echinorhynchus truttae was observed. The presence of a cystacanth of E. truttae in the gammarid E. lusitanicus indicates that this species play a role as an intermediate host in the life-cycle of this parasite in Galicia, where G. pulex (the most frequently reported intermediate host of this parasite species) is lacking.