Hypo-osmotic regulation in entomopathogenic nematodes: Steinernema spp. and Heterorhabditis spp.

Entomopathogenic nematodes were incubated in a balanced salt solution based on soil water analysis, supplemented with different concentrations of sodi um chloride. Two nematode isolates from Malaysia, Steinernema sp. SSL85 (is olate 25) and Heterorhabditis indicus (isolate 11), showed an initial loss of water during the first 6 h of incubation in hyper-osmotic media (200 and 1000 mOsmKg(-1)) followed by a complete recovery of their water content du ring the next 18-48 h. A third Malaysian isolate, Steinernema sp. (M1), sho wed a more limited ability to regulate its water content. Studies on a wild type H. megidis (UK 211) and one desiccation tolerant mutant indicate that the ability for hypo-osmotic regulation does not necessarily involve perme ability differences in the cuticle.