Insect Symbiosis: An Introduction - Insect Symbiosis - page 1

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Insect Symbiosis:
An Introduction

Hajime Ishikawa

CONTENTS

Introduction ........................................................................................................................................1
Types of Associations between Insects and Microorganisms ...........................................................2
Gut Microbes ..............................................................................................................................2
Endoparasitism............................................................................................................................4
Extracellular Symbiosis ..............................................................................................................5
Intracellular Symbiosis ...............................................................................................................5
Mutualistic Symbionts in Insects.......................................................................................................6
Mycetocyte Symbionts................................................................................................................6

.....................................................................................................................................7
Secondary Symbionts .................................................................................................................9
Yeast-Like Symbionts .................................................................................................................9
Intracellular Symbionts of Cockroaches and Termites ............................................................10
Intracellular Symbionts of Coleoptera .....................................................................................11
Intracellular Symbionts of Blood Suckers ...............................................................................11
Guest Microbes in Insects ...............................................................................................................12
Sex-Ratio Distorters..................................................................................................................12

Buchnera

Spiroplasma , an Early Male-Killer...........................................................................................12

Microsporidia, a Late Male-Killer............................................................................................13

..................................................................................................................................14
Conclusion........................................................................................................................................16
References ........................................................................................................................................16

Wolbachia

INTRODUCTION

Over the course of 4 billion years biological evolution has created millions of species on this planet.
Although this is mostly due to repeated and incessant differentiation of preexisting species, species
differentiation was not the only process that produced todayÔs biodiversity. The tendency of nature
to combine two species also promotes biodiversity. Combinations include predatorÏprey relation-
ships, parasitism, and symbiosis. Among these, symbiosis has had major consequences for evolu-
tion. The magnitude of these consequences is immediately evident in light of the origin of eukaryotic
cells, which are chimeras of several prokaryotes (Margulis, 1970; Gray and Doolittle, 1982). As
multicellular organisms, insects as a group seem to be most tolerant of foreign organisms and live
together with many different microorganisms, both inside and outside their bodies, in a variety of
ways (Buchner, 1965). In this sense, insects may provide the best material for examining the
evolutionary signiÝcance of interspeciÝc symbioses.