Symbiotic yeasts in anterior midgut mycetomes of the Asian longhorned beetle (Anoplophora glabripennis)

The highly invasive wood-borer Anoplophora glabripennis (also known as the Asian long-horned beetle, or ALB) was introduced from China and first intercepted in the USA in 1985. The ALB is now a major pest of various maples, horse-chestnuts, willows, and American elms, among other large trees of the Northeastern US. While other cerambycid beetles are known to harbor symbiotic gut yeasts enclosed within specialized cells (mycetomes), molecular analyses of the ALB microbiota have revealed the presence of diverse bacteria and filamentous fungi, but not yeast. The objective of this study was to look for morphological evidence of intracellular symbionts by conducting TEM studies of the ALB anterior mid-gut. We analyzed both sugar maple-fed and diet-fed larvae. Thus far, we have not found evidence of specialized structures housing bacteria, but sugar maple-fed larvae have mycetomes enclosing what appear to be dividing yeast cells.