Hemolymph Changes Resulting from Injection of Escherichia coli Into the Larvae of the Wax Moth, Galleria mellonella (Lepidoptera: Pyralidae)

Shaiemaa Rady,Adel Elsayed,Marwa Radwan,Emad Barakat,Adel Elmahalawy

doi:10.21608/eajbsc.2020.90416

Abstract

The present investigation used Galleria mellonella larvae as an infection model to describe the virulence of Escherichia coli, the most frequent causes of several common bacterial infections in humans and animals. Some hemolymph physical properties such as hemolymph volume - and its relation to body water content, hemolymph density, and pH, along with a quantitative estimation of hemolymph proteins, lipids and carbohydrates were recorded in G. mellonella larvae at different time intervals post-injection with a sub-lethal dose (LD20) of E. coli into the larval hemocoel.A decrease in fresh body weight and body water content with an increase in the hemolymph volume was observed at all time intervals post-larval treatment. This may be due to the loss of tissue water and gained it into the hemolymph. At the same time, bacterial injection decreased the hemolymph density and pH immediately following injection, while the viscosity and acidity of the hemolymph restored its original level with time. The bacterial injection also recorded an obvious decrease in the hemolymph proteins and lipids of the treated larvae at all time intervals post-treatment. This may be due to their elimination and/or their involvement in immune defence reactions or may be due to the intensive consumption and depletion of nutrition during infection. On the contrary, the levels of hemolymph carbohydrates increased at all-time intervals post bacterial injection into larvae. This increase may be due to the release of stored sugars (treehouse) which is responded strikingly due to bacterial infection causing an increase in the level of glucose and glycogen in the hemolymph. These results may lead to a better understanding of the regulatory events and the physiology of infected insects.

Highlights

Disease pathogens can dramatically reduce the fitness of their hosts, and natural selection should favor defense mechanisms that can protect hosts against disease (Medzhitov et al, 2012)
G. mellonella larvae at different time intervals post-injection with a sub-lethal dose (LD20) of E. coli into the larval hemocoel
G. mellonella has proved to be an ideal infection model for studying insect physiology due to a number of reasons: (1) it is one from most widely used insects in physiology, immunology and biochemistry, even when is considered as a pest for the apiculture, (2) it has a fast life-cycle, suitable size of all immature stages, (3) easy reared on natural or artificial diets, (4) there are a lot of similarities between the insect and mammalian gastrointestinal tracts, and (5) The insect fat body functions in drug metabolism in a similar way to the mammalian liver (Kavanagh and Reeves, 2004; Andrejko et al, 2009; Champion et al, 2009; Rejasse et al, 2010; Wand et al, 2011)

Summary

Introduction

Disease pathogens can dramatically reduce the fitness of their hosts, and natural selection should favor defense mechanisms that can protect hosts against disease (Medzhitov et al, 2012). Galleria estimation of hemolymph proteins, lipids and carbohydrates were recorded in mellonella, Escherichia coli, water content, hemolymph volume, density, pH, proteins, lipids, and G. mellonella larvae at different time intervals post-injection with a sub-lethal dose (LD20) of E. coli into the larval hemocoel.

Results

Conclusion