The specific response of gypsy moth A1 neurosecretory neurons to different environmental stressors

Abstract

Changes in the number and morphometric parameters of A1 neurosecretory neurons (nsn) were analyzed in Lymantria dispar 4th instar caterpillars, exposed for 3 days to different stressors: cadmium, high temperature and tannic acid. The relative cytoplasm density of A1 nsn was also estimated. Caterpillars reared on a diet supplemented with cadmium exhibited increased size of A1 nuclei (10 and 250 μg Cd per g of dry food weight), increased number of nucleolii in nuclei and raised relative cytoplasm density in all experimental groups. Cadmium obviously induces intensive synthetic activity in A1 nsn. The second stressor was high environmental temperature of 35°C. Decrease of all analyzed morphometric parameters suggests that acute exposure of 4th instar caterpillars to 35°C, as well as 12 h recovery at optimal temperature of 23°C, reduced the activity of A1 nsn. Tannic acid was added to the artificial diet in the following concentrations: 1%, 2.5% and 5%. All estimated morphological parameters did not change after addition 1 and 2.5% of tannic acid. After addition of 5% of tannic acid, the activity of A1 nsn declined.