Control of the release of digestive enzymes in the cricket Gryllus bimaclatus and the fall armyworm, Spodoptera frugiperda
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چکیده
In Gryllus bimaculatus , more digestive enzymes (amylase, trypsin, aminopeptidase) are secreted in the caecum of fed crickets than in unfed crickets, but the enzymes are released continuously at a basal rate in unfed animals. The rate of synthesis of the enzymes appears to parallel their rate of release. Digestive enzymes are released in response to a specific ratio of nutrients, although a high nutrient component in the food does not necessarily induce a high digestive enzyme release for that component. Rinsed flat-sheet preparations of the caecum are incubated with specific nutrients (carbohydrates and proteins) and various concentrations of a neuropeptide (type-A allatostatin), which affects generally the basal rates of secretion. Both maltose and glucose increase the release of amylase in vitro , but starch produces an inhibition of amylase release at lower concentrations. Bovine serum albumin (BSA), peptone and a mixture of amino acids have almost no effect on the release of aminopeptidase or carboxypeptidase, and only low concentrations of peptone increase trypsin release. High concentrations of both BSA and peptone strongly inhibit trypsin activity, perhaps by excess substrate binding to the trypsin active site. The allatostatin Grybi-AST 5 elevates the release of amylase in vitro , but not of trypsin or aminopeptidase, in 2-day-old fed females. In the caeca from 1-day-old unfed crickets, both amylase and the trypsin release are stimulated in the presence of AST 5. The paracrine AST 5 is probably released from the gut endocrine cells and binds to the enzyme-producing caecal cells.
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Inferring the annual migration patterns of fall armyworm (Lepidoptera: Noctuidae) in the United States from mitochondrial haplotypes
Spodoptera frugiperda (J. E. Smith) or fall armyworm is an important agricultural pest of a number of crops in the western hemisphere. In the United States, infestations in corn acreages extend from the Mexican to the Canadian border. Because fall armyworm does not survive prolonged freezing, the infestations annually affecting most of North America are migrants from southern Texas and Florida,...
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