Ultrastructural features of the gut of Sitophilus granarius (L.) (Coleoptera: Curculionidae) with notes on distribution of proteinases and amylases in crop and midgut

Abstract

In addition to typical columnar cells, dark-staining cells characterized by deep invaginations of basal plasma membranes were found throughout the midgut of adult Sitophilus granarius (L.). These invaginations formed intracellular channels that extended to the perinuclear region and indicated an involvement of these cells in secretion and (or) absorption. Cells with large vacuolelike structures that occasionally filled the entire supranuclear region were found in the anterior midgut, while multicellular crypts and cells that formed apical extrusions into the lumen were common in the posterior midgut. Fine structure of gastric caeca indicated functional differences between those located in anterior and posterior midgut regions. Numerous dark-staining granules were found in apical regions of cells of the anterior caeca, whereas elongated mitochondria were found in microvilli that made up the brush border of posterior caecal cells. Thus, although the midgut is not obviously differentiated into zones, there are different cell types in different regions of the gut involved in digestive and nutrient absorption processes. Evidence indicated that amylase in S. granarius is secreted by salivary glands whereas trypsin and aminopeptidase are secreted by midgut. A slow, continuous secretion of amylase occurs whereas proteinases are secreted in response to ingested food.

Digestive enzyme compartmentalization and recycling and sites of absorption and secretion along the midgut of Dermestes maculatus (Coleoptera) larvae

“…Dermestid digestion differs from that of the Coleopteran putative ancestors (Terra and Ferreira, 2005) in that most terminal digestion of carbohydrates and proteins takes place at the surface of midgut cells. These data do not confirm the earlier suggestion (Terra and Ferreira, 2005) interpret these blebs as part of the normal cell renewal process (Baker et al, 1984;Aumüller et al, 1999). Nevertheless, the presence of secretory vesicles in the blebs, which may be found in midgut lumen along with cell debris, and the signs of that of Tenebrio molitor (Cristofoletti et al, 2001).…”

Digestive enzymes during development of Ceratitis capitata (Diptera:Tephritidae) and effects of SBTI on its digestive serine proteinase targets

“…Activities toward disaccharides (sucrose, maltose and lactose) and polysaccharides (inulin and starch) were determined by the Bernfeld method (1955) as modified by Baker et al (1983). All assays were performed in triplicate.…”

Mitochondria in the midgut epithelial cells of sugarcane borer parasitized by Cotesia flavipes (Cameron, 1891)

“…There is much research that has shown the importance and distribution of mitochondria in the midgut epithelial cells of insects (Mandel et al, 1980;Baker et al, 1984;Hung et al, 2000;Serrão and Cruz-Landim, 2000;Clark et al, 2005). It is known that the mitochondria present in the apical portion of columnar cells are involved in the absorption and metabolism of nutrients, while in the basal portion of columnar cells, this organelle is related to the nutrient and ion transport from the cell to the hemolymph (Lehane and Billingsley, 1996;Hung et al, 2000).…”