The Life Cycle and Development of Aspidogaster conchicola in the Snails, Viviparus malleatus and Goniobasis livescens

Abstract

The life cycle of Aspidogaster conchicola was completed experimentally in 270 days at 20 C in the snail, Viviparus malleatus. Transmission by embryonated, unhatched eggs was demonstrated un- equivocally. Development of A. conchicola from egg to adult involved three growth phases displaying major shifts in allometric growth of the oral disc, ventral sucker, and body. Alveolar development in the ventral sucker was observed to begin at a growth zone behind the anterior lip of the juvenile posterior sucker. From this region, transverse alveoli were formed and pushed anteriorly by formation of subsequent alveoli. Longitudinal septation of the ventral sucker did not occur until 11 or 12 transverse alveoli were formed. Development of the medial septum slightly preceded that of two laterally situ- ated longitudinal septa. Development of A. conchicola in Goniobasis livescens appeared slightly more rapid than in V. malleatus. The name aspidocidium is proposed for the nonciliated juvenile stage of some aspidogastrid species. Since its discovery by von Baer in 1827, Aspidogaster conchicola has been studied only occasionally to determine its development and transmission. Voeltzkow (1888) reported suc- cessful transmission by inserting hatched ju- veniles into the incurrent siphon of presumably uninfected mussels. Several days later, the two experimental hosts each yielded a single im- mature worm from the intestine. Voeltzkow concluded that A. conchicola enters its mussel host via the intestine, penetrating the gut wall