Liu, Q.Z., Dept. of Nematology, ARO, Volcani Center, Bet Dagan 50250, Israel
Piggott, S.J., Dept. of Nematology, ARO, Volcani Center, Bet Dagan 50250, Israel
Solomon, A., Dept. of Nematology, ARO, Volcani Center, Bet Dagan 50250, Israel
Glazer, I., Dept. of Nematology, ARO, Volcani Center, Bet Dagan 50250, Israel

Heterorhabditid nematodes are known to be very poor anhydrobiotes and there is considerable variation in desiccation tolerance among different heterorhabditid isolates. An attempt was made to elucidate the causes for the variation in desiccation tolerance among heterorhabditid strains. The following parameters were considered: Desiccation survival- Exposure of each of the nematode strains to 97% r.h. caused a 10-25% reduction in nematode viability. After additional exposure to 85% r.h. for 24 h, survival rates among heterorhabditid strains were drastically reduced, whereas no further loss in viability was recorded in steinernematid strains. Water content- Initial water content of each of the nematode strains tested ranged between 61% and 67% w/w. After 72 h at 97% r.h., the water content of all strains was reduced by 20%-25% w/w. After further exposure to 85% r.h. for 24 h, the heterorhabditid strains lost an additional 22-24% of their water content, whereas the steinernematids did not lose any significant amount of water. Trehalose and glycogen levels- The concentration of trehalose in the hydrated heterorhabditid strains tested in this study was lower than that of the steinernematids, ranging from 0.17 to 0.23 μg mg-1 protein. Following 72 h at 97% r.h. no significant increase in trehalose concentration was observed with the exception of the SIS-15 strain of Steinernema feltiae. The trehalose level in the latter increased 2.5-fold. Under the same desiccation conditions the levels of glycogen decreased significantly in all of the nematodes tested. While decreases of 2-2.5-fold in glycogen concentration were recorded among the heterorhabditid strains, only 20-30% reduction was measured in the steinernematids.