The influence of thermal acclimation on the amylolytic activity and microanatomy of the alimentary tract of the oribatid mite Galumna elimata (Acari : Oribatei)

The oribatid mite Galumna elimata was reared under laboratory conditions on algae (Protacoccus spp.) at different temperatures (5, 15 and 20 degrees C ). Higher weight-specific amylolytic activity was found in the whole body h omogenates of mites exposed to cold acclimation (5 degrees C, 21 days) in c omparison with individuals acclimated to 15 and 20 degrees C. Accompanying parameters (live body weight, content of total soluble proteins in the body , protein-specific amylolytic activity, presence and composition of food bo luses, activity of mesenteric and caecal wall cells, gregarinid parasitisat ion, number of glycogen granulae and guanine deposits in mesenchymal tissue , presence of proventricular glands) were investigated at all three acclima tion temperatures to explain mechanisms of this change. The acclimation res ponse of weight-specific amylolytic activity was accompanied by elevation o f protein-specific amy lolytic activity. Microanatomical features did not c onfirm any increased secretion activity of mesenteric and caecal cells in c old acclimated animals. Granulation and apocrine secretion of these cells i ncreased with increasing temperature as with food ingestion. The food bolus es contained algae or algae mixed with unknown fungal hyphae in individuals acclimated to 15 and 20 degrees C. The concentrated mucoid substances prev ailed in animals exposed to cold, indicating lower feeding activity at 5 de grees C. Based on these findigs, Lye hypothesised that specific amylolytic activity reflected passively the different changes in protein composition o f the body at different temperatures and its elevation is without direct ad aptive importance.