First record of Phasmarhabditis sp. from eggs of Eobania vermiculata (Muller) snails in Egypt and their response to host size

Background Gastropods are very prevalent animals. In Egypt, terrestrial snails represent important economic pests, infesting and causing severe damages to ornamental plants, orchard trees, vegetables, and field crops. The overuse of molluscicides against these destructive pests leads to more environmental pollution. Therefore, searching for biological control agents became necessary to avoid the hazard of chemical molluscicides. Phasmarhabditis hermaphrodita, isolated from slugs was used as a bio-control agent against snails and slugs. Few investigations available on gastropod egg parasites. Therefore, the present study interested in the isolation of parasitic nematodes from the snail eggs to study their possible role as biological control agents for gastropod pests. Results This is the first record to isolate the snail parasitic nematode, Phasmarhabditis sp., from eggs of the Egyptian terrestrial snail, Eobania vermiculata (Muller). Infectivity of this nematode was investigated for eggs, juvenile and mature snails, E. vermiculata and Limax flavus L. slugs, and also eggs of the non-local species, Achatina fulica Bowdich and one adult of it was only available. The investigation revealed a capability of the isolated nematode to infect and kill E. vermiculata snail, L. flavus slugs, and their eggs. Also, it could infect and kill the eggs of non-local snail species, A. fulica, and its only individual adult available which was obtained from an agricultural quarantine sample. The results indicated also that released individuals of the nematodes, recovered from snails, were significantly larger in size than those recovered from eggs and vice versa. Conclusion It could be concluded that the isolated parasitic nematode may be able to play a role in controlling different stages of the gastropods including eggs. This make the control more effective in protecting host plants before the pest causing damage. The nematode was more effective on local pest species than non-local species. Moreover, the size of the parasite was proportional with the size of the host pest.

Automated summary

This study successfully isolated the parasitic nematode Phasmarhabditis sp. from the eggs of the Egyptian terrestrial snail Eobania vermiculata (Muller) for the first time. The results showed that these parasitic nematodes have the ability to infect and kill different stages of gastropods, with a better effectiveness on local pest species compared to non-local species, and the size of the parasite is proportional to the size of the host pest.