Comparative aspects of plant cell wall digestion in insects

Abstract

Although many phytophagous and wood-eating invertebrates form their own cellulases, there is an overwhelming variety of symbioses between plant- and wood-utilising insects and microorganisms. In one type of symbiosis (endosymbiosis), insects (rhinoceros beetle, cockroach, lower termites) host cellulolytic protozoa and/or bacteria in the hindgut. In a number of insect taxa (higher termites, cerambycid beetles) cellulose digestion is aided by the ingestion of fungal tissues for the delivery of certain components of the cellulase complex needed to complement the host enzymes for action on crystalline forms of cellulose. While the bulk of the plant lignin is not significantly degraded under the conditions characteristic of gut contents of herbivores, some groups of insects are thought to be able to digest a part of this non-carbohydrate polymer.