Rhabditis maupasi: occurrence in food snails and cultivation

Rhabditis maupasi, a nematode, inhabits the mantle cavity of terrestrial snails, Helix aspersa, that are imported from Morocco and sold in the food markets of New York City. Most of the nematodes found in living snails are stage-3 larvae which mature and reproduce after the snail has died and decayed. The nematodes were isolated from snails and cultivated with a microflora and then in species isolation, i.e., axenically. Sterile slices of rabbit kidney supported by agar slants served as the initial culture system. Subsequently, a liquid medium was used that contained raw rabbit liver extract. When, instead, raw snail extract was substituted in the liquid medium, nematode larvae did not mature unless the snail extract was digested secondarily or inactivated by heating. Nematodes grow abundantly in dead snails and in treated snail extract but not in living snails or in raw snail extract. The reason is probably not the nematodes' lack of suitable digestive enzymes for snail tissue nor the absence of adequate nutrients in living, microbially poor snails, but rather the presence of an inhibitor in snails.