Endocrine Abstracts

The gypsy moth, Lymantria dispar L., is one of the most destructive phytophagous pests of the northern hemisphere. It shows a tremendous capacity to increase in numbers, and feeds on a wide range of trees and shrubs. However, several different systems driving feeding behavior and digestion of Lymantria dispar L. have not yet been elucidated.

Ghrelin along with several other hormones has significant effects on appetite and growth in humans and animals. The aim of our study was to examine changes in nutritional indices (relative growth rate-RGR, relative consumption rate-RCR, efficiency of conversion of ingested food-ECI, efficiency of conversion of digested food-ECD), relative midgut mass, total proteases, leucine aminopeptidase and trypsin activities in the midgut and fat body mass of 4th instar caterpillars of the pest insect, Lymantria dispar L. after ghrelin treatment. Four subpicomolar injections of ghrelin (0.3 pmol) or physiological saline (control) were applied every 24 h to two separate groups of fifteen caterpillars. The nutritional indices, RGR, RCR, ECD and ECI were higher in the ghrelin treated than in the control group. Repeated administration of ghrelin in subpicomolar doses also elevated relative midgut mass, induced digestive enzyme activities and increased fat body mass. Such information provides more evidence for the application of these relatively simple model systems in future studies of the mechanisms underlying digestion in complex organisms. Understanding of the processes of feeding regulation should also have practical applications in biological control of its population number.