Peritrophic membrane role in enhancing digestive efficiency. Theoretical and experimental models
Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, C.P. 26077, 05513-970, São Paulo, Brazil. Journal of Insect Physiology
(Impact Factor: 2.47).
09/2008; 54(10-11):1413-22. DOI: 10.1016/j.jinsphys.2008.08.002
The peritrophic membrane (PM) is an anatomical structure surrounding the food bolus in most insects. Rejecting the idea that PM has evolved from coating mucus to play the same protective role as it, novel functions were proposed and experimentally tested. The theoretical principles underlying the digestive enzyme recycling mechanism were described and used to develop an algorithm to calculate enzyme distributions along the midgut and to infer secretory and absorptive sites. The activity of a Spodoptera frugiperda microvillar aminopeptidase decreases by 50% if placed in the presence of midgut contents. S. frugiperda trypsin preparations placed into dialysis bags in stirred and unstirred media have activities of 210 and 160%, respectively, over the activities of samples in a test tube. The ectoperitrophic fluid (EF) present in the midgut caeca of Rhynchosciara americana may be collected. If the enzymes restricted to this fluid are assayed in the presence of PM contents (PMC) their activities decrease by at least 58%. The lack of PM caused by calcofluor feeding impairs growth due to an increase in the metabolic cost associated with the conversion of food into body mass. This probably results from an increase in digestive enzyme excretion and useless homeostatic attempt to reestablish destroyed midgut gradients. The experimental models support the view that PM enhances digestive efficiency by: (a) prevention of non-specific binding of undigested material onto cell surface; (b) prevention of excretion by allowing enzyme recycling powered by an ectoperitrophic counterflux of fluid; (c) removal from inside PM of the oligomeric molecules that may inhibit the enzymes involved in initial digestion; (d) restriction of oligomer hydrolases to ectoperitrophic space (ECS) to avoid probable partial inhibition by non-dispersed undigested food. Finally, PM functions are discussed regarding insects feeding on any diet.
Available from: Alex Córdoba-Aguilar
- "The peritrophic membrane/matrix (PM) is a chitin-protein matrix that surrounds the food bolus in the midgut of the majority of insects (Bolognesi et al., 2008). "
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ABSTRACT: The peritrophic matrix is a chitin-protein structure that envelops the food bolus in the midgut of the majority of insects, but is absent in some groups which have, instead, an unusual extra-cellular lipoprotein membrane named the perimicrovillar membrane. The presence of the perimicrovillar membrane (PMM) allows these insects to exploit restricted ecological niches during all life stages. It is found only in some members of the superorder Paraneoptera and many of these species are of medical and economic importance. In this review we present an overview of the midgut and the digestive system of insects with an emphasis on the order Paraneoptera and differences found across phylogenetic groups. We discuss the importance of the PMM in Hemiptera and the apparent conservation of this structure among hemipteran groups, suggesting that the basic mechanism of PMM production is the same for different hemipteran species. We propose that the PMM is intimately involved in the interaction with parasites and as such should be a target for biological and chemical control of hemipteran insects of economic and medical importance.
- "The insect midgut epithelium lacks a mucus coating, the peritrophic membrane is considered to be the analogous to that of the mucus that lubricates the mucosa, protecting against food abrasion and microorganisms (Caldeira et al. 2007, Bolognesi et al. 2008). However, the peritrophic membrane also has specific functions depending on the fact that it compartmentalizes the midgut lumen into an endoperitrophic space (inside peritrophic membrane) and an ectoperitrophic space (space between peritrophic membrane and midgut epithelium ; Bolognesi et al. 2008). This functions to 1) prevent non-specific food binding onto the cell surface; (2) restrict oligomer hydrolases to the ectoperitrophic space; and (3) prevent enzyme excretion by allowing enzyme recycling (Caldeira et al. 2007). "
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ABSTRACT: The analyses of the insect species found on decomposing remains may provide useful information for the estimation of the minimum time elapsed since death and other parameters, such as causes and circumstances of death. The majority of research has focused on the early colonizing species, typically blowflies, while research concerning late colonizing insects is currently sparse. Dermestid beetles of the genus Dermestes L. (Coleoptera: Dermestidae) are one of the predominant insect species associated with decomposing remains during dry decay and skeletal stages of decomposition. In some dry environments, Dermestes species are likely to be the only necrophagous insects feeding on the decomposing remains. Furthermore, Dermestes species (immature and adults), their remains (cast skins and fecal material), and their artifacts (pupal chambers) are frequently found associated with ancient remains (e.g., mummies, fossils). Dermestes species have a worldwide distribution and are considered important in decomposition processes, forensic investigations, and economically as a known pest of stored products. Despite their recognized forensic importance, there is limited data documenting the ecology, biology, and the growth rates of the forensically relevant species. The aim of this review is to provide a comprehensive synopsis on the available literature concerning Dermestes species associated with forensic cases. In particular, aspects of colonization behavior, growth rates for forensic taxa and potential best practice guidelines for forensic casework encompassing late colonizing Dermestes species are discussed.
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Available from: Renata Ávila Ozório
- "The compartmentalization of digestion and the existence of the endo-ectoperitrophic circulation increase digestive efficiency by allowing the removal of oligomers obtained in the initial digestion and reutilizing digestive enzymes to obtain new oligomers, which are hydrolyzed within the ectoperitrophic space. Since the enzymes produced are not evacuated, but recycled, there is considerable energy saving (Bolognesi et al., 2008). Further research, however, is needed to better understand how the endo-ectoperitrophic circulation mechanism affects the shrimp's digestive physiology and how this could be manipulated in order to maximize the output performance of shrimps in captivity. "
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ABSTRACT: The study was developed to evaluate the influence of diet supplementation of a polysaccharide extract from the microalgae Porphyridium cruentum, on weight gain, digestive enzyme activity, and Litopenaeus vannamei juvenile survival. The polysaccharides crude extract from microalgae P. cruentum was added at different concentrations (0, 0.5, 1, 1.5, and 2.0%) in a commercial diet and provided to juvenile L. vannamei (6.6 ± 0.2 g). The shrimps (n = 2,000) were fed ad libitum for 30 days in circular tanks with 12 m2 of bottom area (100 shrimp tank-1) and environmental variables (temperature, salinity, dissolved oxygen, photoperiod and levels of total ammonia) were controlled. The supplemented diet with 1% crude extract was responsible for the biggest weight gain (7.28 g) in 30 days. The shrimp body muscle centesimal composition and survival were not affected by the polysaccharide extract supplementation. It was observed a shift in the activity of digestive enzymes from the hepatopancreas to the anterior midgut and mid midgut portions in shrimps with diet supplemented with 1% polysaccharide extract, which may have contributed to a better digestive efficiency. The results indicate that dietary supplementation with crude extract of P. cruentum polysaccharides in a range between 1 and 1.5% increases weight gain and enhances the activity of digestive enzymes in L. vannamei juveniles.
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