Permeability of the infective juveniles of Steinernema carpocapase to glycerol during osmotic dehydration and its effect on biochemical adaptation and energy metabolism

Permeability of the sheath and cuticle of the infective juveniles (IJs) of Steinernema carpocapsae to glycerol and its effect on biochemical adaptatio n of the IJs to osmotic dehydration were examined by incubating both sheath ed and exsheathed IJs in glycerol-d(5) solution then monitoring the changes in levels of deuterium labelled and non-labelled glycerol and trehalose. E nergy metabolism of the IJs during osmotic dehydration and subsequent rehyd ration and the effect of the permeated glycerol on this process were invest igated by examining and comparing the changes in mean dry weight and key bi ochemical composition of the IJs dehydrated in glycerol and sodium chloride solutions. The results show: (1) similarly to evaporative dehydration, osm otic dehydration induces IJs to synthesise the protectants glycerol and tre halose; (2) glycerol permeates the sheath and the cuticle into the body of IJs during dehydration in glycerol solution. Part of the permeated glycerol plays a role as protectant like that synthesised by IJs from their energy reserve materials while part is incorporated into trehalose: (3) the sheath reduces the rate of permeation of glycerol and therefore affects the equil ibrium glycerol and trehalose levels of the IJs and also the time needed to reach the equilibrium levels; (4) the reduction in mean dry weight and lip ids of the IJs during dehydration in glycerol solution is substantially les s than those dehydrated in sodium chloride solution. Both the total protect ant level and the ratio of glycerol to trehalose of the IJs dehydrated in g lycerol solution are higher than those dehydrated in sodium chloride soluti on; (5) glycogen reserves of the IJs play a role as a buffer reservoir of t he protectants during both dehydration and rehydration but the principal so urces of the protectants during dehydration are more likely to be lipids an d proteins rather than glycogen. (C) 2000 Elsevier Science Inc. All rights reserved.