CONICET | Buscador de Institutos y Recursos Humanos

Haplosporidium patagon was found parasitising: Siphonaria lessonii and Siphonaria lateralis, two siphonariid gastropods co-occurring on the littoral rocky shore at Puerto Deseado, Santa Cruz, Argentina. Gastropods from two habitats representing two different levels of environmental harshness were studied, in both cases S. lesonnii showed higher value of 14-month prevalence (3.78%) of infection than S. lateralis (0.13%). Quite different values of period prevalence of infection were observed according to the sampling site: the more restrictive habitats (exposed for long periods to air drying during low tides, higher ultraviolet and high ranges of temperature variation) showed the higher prevalence values (5.99%). The infection showed a definite seasonal pattern, the point prevalence peaked in the austral autumn (11.5% site 1 and 0.83% site 2) and winter seasons (13.79% site 1 and 2.13% site 2). Statistical differences in point prevalence were found between values corresponding to the austral spring and winter seasons. The presence-absence of H. patagon did not vary significantly whith the shell length, however, mid to large size classes were consistently more affected. The infection affected the digestive gland, whose normal histology resulted deeply modified. The hermaphroditic gonad was also affected; the female germinal cells disappeared or remained represented by few primary or previtelogenic oocytes, and the vitellogenesis was inhibited. The male germinal epithelium, as well as the spermatogenesis and spermiogenesis processes and associated organs (seminal vesicles and seminal receptacles) were not affected in their function. The glandular pallial complex of the reproductive system was also affected, with a significant reduction in its development in parasitized gastropods. Sporocysts of H. patagon also invaded the supporting connective tissues of both kidney and pseudobranch.