Effects of ecdysone, juvenile hormone and haemolymph transfer on cryoprotectant metabolism in diapausing and non-diapausing pupae of Pieris brassicae

Abstract

Hormone applications and haemolymph transfer were used to study the control of cryoprotectant synthesis in diapause and non-diapause Pieris brassicae. Diapause pupae are 24% heavier than non-diapause pupae 5 days after pupation and have 10 times more sorbitol and 8 times more mannitol in the absence of low temperature exposure. In diapause pupae, sorbitol increases 8-fold from 5 to 55 days at 20°C. Other carbohydrates such as glucose, mannose, glycerol, mannitol and inositol also increase during this time. Injection of ecdysone (500 ng) terminates diapause at all stages investigated but does not affect development or carbohydrate levels in non-diapause pupae. Diapause pupae show significant decreases in glucose, mannose, sorbitol and mannitol after ecdysone injection, whilst glycerol increases. Juvenile hormone application (500 ng) has no effect on the development of diapause or non-diapause pupae but the latter show significant increases in glucose and glycerol whilst sorbitol levels are unchanged. In contrast, diapause pupae show significant increases in sorbitol whilst glycerol decreases. Haemolymph transfer did not influence carbohydrate levels. Implications for the relationship between cryoprotectant synthesis and diapause are discussed and a model is proposed.