Influence of the trematode Aphalloides coelomicola Dollfus, Chabaud & Golvan, 1957 on the fecundity and survival of Pomatoschistus microps (Kroyer, 1838) (Teleostei : Gobiidae)

Monthly data collected during 1993 in the Vaccares lagoon (Rhone Delta, Fra nce) were used to investigate the influence of the trematode Aphalloides co elomicola on the survival of the common goby. Pomatoschistus microps, which acts both as second intermediate and definitive host. Prevalence of the pa rasite did not increase with fish size in either sex. Mean abundance and va riance to mean abundance ratio gave evidence that the trematode could have an impact on host mortality. Gonad weight of parasitized females was reduce d and the parasite seemed to provoke a gonadal regression above a certain p arasitic biomass. Fecundity and egg diameters did not differ between parasi tized and unparasitized females, we thus hypothesize that the energy conten t cf eggs (composition in lipids and proteins) was probably modified as an adaptation to energy losses. Prevalence of infection in males compared to f emales and influence of the parasite on host survival and reproductive effo rt are discussed.