Further Studies on the Rectal Complex of the Mealworm Tenebrio molitor, L. (Coleoptera, Tenebrionidae)

摘要: An electron microscopical study has been made of the rectal complex. The perinephric membrane is a complicated structure which, in posterior region, comprises an inner and outer sheath separated by space containing tracheolar end cells. formed single layer cells covered external basement membrane. multi-laminate up many thin, cellular layers which places are reduced to closely apposed plasma membranes. Anteriorly number, but each greater thickness; they finally terminate where applied intestine. Posteriorly makes contact with epithelium. earlier description identified three spaces within complex: perirectal, subepithelial peritubular spaces. first two true intercellular spaces, bounded membranes, so-called occupied necrotic interrupted leptophragmata. Each leptophragma prominent electron-dense ring into laminae inserted. forms blister over completely noncellular this region. At base covers itself, body cell projects lumen tubule, thin cytoplasm lying beneath Both itself bear microvilli. normal complement mitochondria, these do not invade In last respect ordinary tubule differ from that most their microvilli contain connexions between mitochondrial have poorly developed endoplasmic reticulum filled numerous small granules; basal infoldings restricted those parts face perirectal space. permeability re-investigated it shown more permeable water solutes at anterior end, as might be expected if were main barrier. Using preparations isolated volumes haemolymph or other media complex takes potassium against gradient concentration. some 50 mV positive medium, so uptake must active. freely chloride ion appears enter passively. A model mechanism proposed, whose feature high osmolarity fluids brought about inward secretion chloride, unaccompanied water, This should result fall medium. substantial observed on occasion, experiments barely detectable. It believed impermeability leptophragmata rapidly lost deteriorating preparation.