The effect of heat stress on the activity of A1 and A2 neurosecretory neurons of Morimus funereus (Coleoptera : Cerambycidae) larvae

Abstract

A study on the effect of heat stress on the activity of the medial A1 and A2 neurosecretory neurons (NSN), and the activity of midgut a-amylase and protease was performed on the fifth larval instar of Morimus funereus. Exposure of the larvae to 35 degreesC led to a decrease in the activity of both Al and A2 NSN, the former being more marked than the latter. These neurons responded differently to heat stress in terms of neurosecretory material synthesis and release. The changes in the size of both Al NSN and their nuclei and protease activity in the larvae exposed to elevated temperature were significantly correlated, which suggests that Al NSN play a role in the regulation of the activity of this enzyme during heat stress. The significant correlations between the size of A2 NSN and protease activity in the controls, and the size of both A2 NSN and their nuclei and amylase activity in larvae exposed to heat stress, similarly may mean that A2 NSN regulate both digestive enzyme activities depending on environmental temperature.