FACTORS AFFECTING CARBOHYDRATE AND FREE AMINO-ACID CONTENT IN OVERWINTERING LARVAE OF ENOSIMA-LEUCOTAENIELLA

Amounts of several metabolites were measured in overwintering larvae o f Enosima leucotaeniella acclimated to temperatures between -5 and 15 degrees C for 30 days. In the diapausing stage, cold hardiness, as sho wn by the survival rate, began rising below 15 degrees C. Glycogen con tent decreased as the temperature decreased from 10 to 0 degrees C. Tr ehalose content rose as the temperature decreased from 15 to 5 degrees C, but remained unchanged as the temperature decreased from 5 and 0 d egrees C. Twenty-eight free amino acids were detected in the haemolymp h; levels of proline, glutamine and glutamic acid increased at high te mperatures, but alanine increased at low temperatures, especially as t emperature decreased from 5 to 0 degrees C. Lipid content was unchange d by the different acclimation temperatures. The effects of temperatur e, diapause and aerobic conditions on the levels of carbohydrates and amino acids in overwintering larvae were analyzed. Alanine levels rose at low temperature only when the larvae were in the diapausing stage. The level of trehalose rose at low temperature in both the diapausing and post-diapausing stages, although it was higher at aerobic conditi ons in the post-diapausing stage. These results suggest that efficient trehalose synthesis occurs under the combination of low temperature a nd aerobic conditions of the post-diapausing stage, so that cold hardi ness in overwintering E. leucotaeniella larvae may rise to a high leve l in winter. (C) 1997 Elsevier Science Ltd. All rights reserved.