Study on the life cycle of a sexually transmitted nematode parasite of a terrestrial snail

A technique for the artificial infection of the snail Helix aspersa by its parasite the nematode Nemhelix bakeri is described. The snail is relaxed by injection of an anesthetic, and 1 gravid female worm is introduced into the genitalia through the genital pore. Half of the injected snails were successfully infected. Following the course of infection over time indicated a 1:1 sex ratio, that the maximum number of progeny produced by injected female worms was 7, and that the development time of female worms was 56 days. The first generation of gravid females was found 100 days after infection. A survey of naturally parasitized snails was also conducted. The sex ratio of worms was in equilibrium, with a mean number of 2.4 larvae per female. The development time (56 days) and the body size (2.47-4.00 mm) of female N. bakeri are similar to those of a related species Cosmocercoides dukae (52-57 days and 1.66-4.34 mm), although the life cycle and biogeographic distribution for each of them are distinct.