Fréquence et degré d'expression du pseudohermaphrodisme chez quelques Prosobranches Sténoglosses de la Baie de Morlaix et de la Manche. I : Situation au printemps de 1988

The frequence of the pseudohennaphroditism is analysed in 589 individuals of 5 Prosobranch species of the Bay of Morlai x (namely Roscoft) and of the french coast of the Channel (Port-en-Bessin, Coutainville, Granville). The pseudohermaphroditism is demonstrated for the first time in Hil1ia (Nassaril/s) il/crassala and confinned for Roscoff in NI/cella lapillI/s, Ocel1ebra eril1acea , Bl/ccil1l/l11 I/l1dall/lII and Hil1ia (Nassaril/s) relicl/lala (Tabl. II and lIl ). Six different morphological types are di stinguished and the differences of the species are described (Table III and Fig. l) ; the appearance of pseudohermaphroditic?ô § without a penis , but with a vas deferens of a various length is presented for the first time. The accentuated occurence of the pseudohennaphroditi sm in marinas and ports, already known by lhe lilerature, is confirmed as weil in respect to the percentual frequence as to the intensity of morphological expression (Tabl. Il and 1II ). The continuous expans ion of the pseudohermaphroditism is demonstrated ; in several locali ties, where il was between 1972 and 1978 not present (Granville, Coutainville) or only in lower percentages, it is Clemonstrated in 1988 for the first lime or confirmed in higher leve ls.