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 4 th 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 4 th 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.

Tannic acid modulates the activity of bombyxin- and PTTH-producing neurons in Lymantria dispar L. (Insecta: Lepidoptera) caterpillars

“…Perić-Mataruga and Lazarević (2004) showed changes in the number and activity of medial neurosecretory neurons upon feeding caterpillars locust leaves rich in tannins. Changes in the activity of A1 medial nsn (Ilijin 2009) and L1 dorsolateral nsn (Ilijin et al 2014) in L. dispar caterpillars, upon feeding with a tannin-supplemented artificial diet, were previously detected.…”

“…Bombyxin or a small form of prothoracicotropic hormone (PTTH) also regulates carbohydrate homeostasis (Satake et al 1997). L2`nsn were found to be immunopositive for a big PTTH form in L. dispar caterpillars (Ilijin et al 2014). This PTTH regulates metamorphosis in insects (Rybczynski 2005), and activation of the stress protective mechanism (Ivanović & Janković-Hladni 1991).…”