Digestive Enzymes of Fungus-Feeding Beetles

Abstract

The digestive capabilities of 11 species of fungus-feeding beetles, representing five families, were examined. All 11 species possess a well-developed capacity to digest fungal protein, and all but one species are able to digest β-1, 3-glucans, which are major components of fungal cell walls. Seven of the species can digest α-1, 4-glucans, which serve as storage polysaccharides in fungi, and a few species have low levels of chitinolytic activity. No activity toward the common cell wall polysaccharides of higher plants, namely, cellulose, hemicellulose, or pectin, was detected in any of the beetles' guts. Slightly acidic conditions prevail in the guts of these insects. The absence of regions of high alkalinity in the beetles' guts is compatible with the absence from their fungal diet of tannins or other polyphenols which bind to protein under acidic, neutral, or slightly alkaline conditions. Thus, the digestive system typical of fungivores is distinct from that of herbivores, both in terms of the enzymes present and the conditions of alkalinity maintained within the gut. It is further noted that many invertebrate detritivores possess digestive capabilities which are qualitatively more similar to those of fungivores than herbivores.