A complex of fungi mutualistically involved in the nutrition of the ambrosia beetle Xyleborus ferrugineus

Abstract

Paired oral mycangia (organs in which mutualistic fungi are perpetuated) were present in both sexes of the ambrosia beetle Xyleborus ferrugineus. The mycangia of stock culture beetles bore a complex of fungi, yeast, and bacteria. Fusarium solani was the dominant fungal symbiote, but a Cephalosporium sp., and a Graphium sp. also were isolated from 50% and 20% of the beetles, respectively. All three fungi formed “ambrosia” growth on the walls of brood tunnels when inoculated singly into tubes of medium bearing one female beetle previously freed of fungi. The fungus that was inoculated into a given tube of medium was the only fungus subsequently recovered from mycangia of adult beetles in that tube. Each fungus grew in characteristic forms in the mycangia of the beetles. Each of the three fungi provided the nutrients or concentrations of nutrients, not contained in the medium, that were essential to reproduction by the insect.