Relative Dominance of the Mold Fungus, Raffaelea sp., in the Mycangium and Proventriculus in Relation to Adult Stages of the Oak Platypodid Beetle, Platypus quercivorus (Coleoptera; Platypodidae)

Abstract

Microorganisms associated with the oak platypodid beetle, Platypus quercivorus (Murayama), were isolated from the mycangium of adult females, from the proventriculus of adults of both sexes, and from galleries in the period before dispersal. Fungi isolated from female mycangia were separated into three groups: Raffaelea sp., yeasts (mainly Candida spp.), and other species. Raffaelea sp. was isolated predominantly from the teneral stage to the dispersal stage, but was not isolated from the mycangia of mother beetles in new galleries. Yeasts were isolated in every beetle stage tested and their isolation rate was over 80% from the teneral stage to the dispersal stage. All three fungal groups were found in the female proventriculus. Raffaelea sp. was isolated only in the dispersal stage at a rate of 40%, whereas the isolation rate of yeasts gradually increased beginning in the mature stage and reached 100% in the rearing stage. In contrast, in the male proventriculus, only Raffaelea sp. and yeasts were isolated in the dispersal and rearing stages. The isolation rate in the rearing stage of Raffaelea sp. was less than 20%, but that of yeasts was 100%, although these rates were almost the same in the dispersal stage. Raffaelea sp. and yeasts were also isolated from cradles containing eclosing pupae. These results suggest that P. quercivorus acquires Raffaelea sp. and yeasts in their mycangia from the cradles immediately after eclosion, and maintain them to the dispersal stage. Then, they transmit these fungi from old to new galleries by way of mycangia, and possibly the digestive system.

Key words:

• mycangium
• Platypus quercivorus
• proventriculus
• Raffaelea
• yeasts