Sur la présence d'une cercaire de trématode chez cardium edule l. dans le bassin d'arcachon

The progressive reduction of the Cardium edule's (shell) areas of distribution in the Arcachon basin had led us, at the beginning of the year 1968 and after fishing season to become interested in the problem of the survival and exploitation of the only existing significant site in the most oceanic part of the bay, the Arguin bank's cove. The topographical features of the environment have been described elsewhere (DELTREIL and His, 1968). During this preliminary study, our observations had enabled us to define the factors responsible for the survival and growth of this population of shells. Competition from Mytilus edulis and the instability of the beach mean that maintaining this site is closely linked to a regular and abundant annual intake of spat. It was during examination of sex products that we discovered the presence of a larval form of trematode that was massively invading the gonad of some individuals. The morphological nature of this parasite enabled us to identify it; it is the cercaria of Bucephalus haimeanus LACAZE-DUTHIERS (1854). It is the typical form of an entire family of digenetic trematoda, the Bucephalidae, larval-state parasites of several lamellibranchiate molluscs. To our knowledge, this parasitism in marine species has not given rise in France to any special study since HUET (1887-1888). However, abroad, its discovery in several lamellibranchiates of commercial interest, Ostreidae in particular, explains the research that has been devoted to it. It seemed worthwhile to us to summarise the results obtained to date, as well as the numerous controversies to which they have given rise. We will describe, in short, the bucephalus that we found and we will examine the incidence of parasitism in Cardium edule on the Arguin bank.