Destruction of peritrophic membrane and its effect on biological characteristics and activity of digestive enzymes in larvae of the Indian meal moth, Plodia interpunctella (Lepidoptera: Pyralidae)

Seyede MINOO SAJJADIAN,Vahid HOSSEININAVEH

doi:10.14411/eje.2015.046

Abstract

The mid gut in insects is usually lined with a peritrophic membrane (PM), which protects it from microbial infections and physical contact with ingested food. Calcofluor is an optical brightener that has strong chitin-binding properties, which disrupt the chitin-protein structure of PM. In this study, we investigated the effects of calcofluor on the structure of the PM, activity of some common digestive enzymes and biological characteristics of the Indian meal moth, Plodia interpunctella (Lepidoptera: Pyralidae). Twenty hours after feeding on a calcofluor-containing diet, the PM was completely eliminated. We recorded significant effects of calcofluor on the activity of digestive enzymes in the mid and hindguts of larvae. In both these regions of the gut, in particular, there were significant increases in the activity of α-amylase, α-galactosidase and trypsin. The activities of α-glucosidase and β-glucosidase in the midgut of treated larvae were lower than in the control, but were significantly higher in the hindgut of treated larvae. The larvae that fed on on calcofluor for 20 h, took longer to complete their larval and pupal stages, were lighter in weight and fewer reached maturity and laid fewer eggs. Results of this and previous studies highlight the crucial role of PM in enzyme recycling and digestion. PM disruption may negatively affect insect development on the one hand, by decreasing the efficiency of food digestion and, on the other, by increasing the costs associated with an increased enzyme demand and disrupted enzyme recycling mechanism.

Highlights

The alimentary canal of insects is divided into three distinct regions, the fore, mid and hindgut, based on their embryonic origins, structures and physiological functions
The aim of this study was to explore the effects of calcofluor on peritrophic membrane or matrix (PM) development in the Indian meal moth, Plodia interpunctella (Lepidoptera: Pyralidae), an important polyphagous pest of many stored products worldwide
The larvae of P. interpunctella fed on calcofluor for 5 h showed slight changes in PM structure (Fig. 1b)

Summary

Introduction

The alimentary canal of insects is divided into three distinct regions, the fore, mid and hindgut, based on their embryonic origins, structures and physiological functions. In direct contact with the gut contents the midgut faces constant physical and chemical challenges from indigested food (Lemaitre & Miguel-Aliaga, 2013). PM surrounds the food eaten by insects and prevents it from coming into direct physical contact with the microvillar cells (Wang & Granados, 2001). This anatomical structure has an important role in enhancing digestive efficiency (Bolognesi et al, 2008). The PM contains pores, which are permeable to some digestive enzymes and the products of digestion This selective permeability creates a compartmentalization into an endoperitrophic space and ectoperitrophic space (Klowden, 2007). A relatively wide variation exists in the size of pores among different insects: ranging, for example, from 7–7.5 nm in the moth Erinnys ello (Lepidoptera: Sphingidae) to 150 and 200 nm in cockroaches and grasshoppers, respectively (Santos & Terra, 1986)

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