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 int roduced into the genitalia through the genital pore. Half of the injec ted snails were successfully infected. Following the course of infecti on over time indicated a 1:1 sex ratio, that the maximum number of pro geny produced by injected female worms was 7, and that the development time of female worms was 56 days. The first generation of gravid fema les was found 100 days after infection. A survey of naturally parasiti zed snails was also conducted. The sex ratio of worms was in equilibri um, 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 sim ilar to those of a related species Cosmocercoides dukae (52-57 days an d 1.66-4.34 mm), although the life cycle and biogeographic distributio n for each of them are distinct.