Ultrastructure of the mycangium of the southern pine beetle, Dendroctonus frontalis (Coleoptera: Curculionidae, Scolytinae): complex morphology for complex interactions

Abstract

Yuceer, C, Hsu, C.-Y., Erbilgin, N and Klepzig, K.D. 2011. Ultrastructure of the mycangium of the southern pine beetle, Dendroctonus frontalis (Coleoptera: Curculionidae, Scolytinae): complex morphology for complex interactions. —Acta Zoologica (Stockholm) 92: 216–224. The southern pine beetle (SPB) (Dendroctonus frontalis Zimmermann) is the most economically important pest of southern pine forests. Beetles carry fungal cells within specialised cuticular structures, called mycangia. Little is known about the mycangia ultrastructure or function. We used cryo-fracturing and scanning electron microscopy to examine the ultrastructural features of SPB mycangia and surrounding tissues. Mycangia, one on each side of anterior portion of the prothorax, are terminated on the dorsal side at a ‘mycangial bridge’. This sclerotised mycangial bridge does not appear to provide a passage between the two mycangia, suggesting that each mycangium functions independently. Mycangia are surrounded by abundant tracheoles connecting the structures to the outside via openings within the prothorax. Previously unknown pits overlying the mycangial gland cells were also observed in both the inner wall and anterior fold of prothorax. We hypothesise that these openings and pits may play roles in determining which fungi enter, and grow within, the mycangium.