Low temperature induced cryoprotectant synthesis by the infective juveniles of Steinernema carpocapsae: Biological significance and mechanisms involved

The infective juveniles (IJs) of Steinernema carpocapsae synthesised trehal ose but not glycerol at low temperatures. Equilibrium trehalose levels were temperature dependent. When the IJs were incubated aerobically in tap wate r at temperatures ranging from 2 to 14 degrees C, their trehalose levels in creased from 1.9% dry weight to equilibrium levels ranging from 3.4% at 14 degrees C to 6.0% at 5 similar to 8 degrees C. Noticeable increases in treh alose levels in the IJs of four other species of entomopathogenic nematodes (ENs) exposed to 5 degrees C indicated that this is likely to be a common characteristic of the IJs of ENs. Cold induced IJs had a much higher tolera nce to severe osmotic dehydration. When aging IJs, which have lower energy reserves than fresh ones, were exposed in the same way to 5 degrees C for 7 days, their trehalose levels were lower than those of fresh IJs but the su rvival rates of the IJs did not drop substantially. Changes in lipid, glyco gen and protein levels of IJs during cold induction and subsequent recovery indicated that trehalose was not synthesised from glycogen, but from lipid s and/or proteins. The processes involved in low temperature induced cryopr otectant synthesis by ENs are discussed and compared to those found in inse cts.