Osmotic induction of anhydrobiosis in entomopathogenic nematodes of the genera Heterorhabditis and Steinernema

The osmotic tolerance of different species and isolates of entomopathogenic nematodes of the genera Steinernema and Heterorhabditis was examined using an osmotic solution to induce anhydrobiosis in these nematodes. Infective juveniles (IJs) of the species and isolates were exposed for 72 h to the osmotic solution consisting of a mixture of fortified artificial seawater and glycerol at 15 °C. Morphological appearance, motility, survival, heat tolerance and infectivity of the osmotically treated IJs were investigated. The results indicated that different species or isolates of nematodes showed differences in osmotic tolerance. Some species, such as S. carpocapsae All and S. scapterisci SS, adapted well to the osmotic solution. Their mortality was below 2%, and their heat tolerance was improved. Other species, including S. feltiae SN, S. longicaudum X-7 and H. bacteriophora H06, were moderately tolerant to the osmotic solution, suffering less than 20% mortality. However, the osmotic treatment greatly enhanced their heat tolerance. Although the infectivity of some osmotically treated isolates was lower than that of non-treated nematodes, the osmotically treated IJs retained their infectivity to Galleria mellonella larvae.