Cold-induced glycerol accumulation by Ostrinia nubilalis larvae is developmentally regulated

Ostrinia nubilalis larvae reared under both nondiapause and diapause-inducing conditions were chilled at 5°C for various periods and their haemolymph glycerol concentrations were measured enzymatically. The ability of fifth (final) instars to accumulate glycerol was dependent upon cold stress but not the diapause state. Furthermore this response was independent of any cold-induced release of cephalic or thoracic hormones. The capacity of O. nubilalis larvae to express cold-induced glycerol accumulation was found to require ecdysis from the fourth to fifth instar. Eggs as well as second, third and fourth instars were completely incompetent. These results indicate that, at the biochemical level, a specific developmental programme or sequence is required for O. nubilalis to demonstrate this response to cold stress.