Morphology, molecular characteristics and prevalence of a Cystosporogenes species (Microsporidia) isolated from Agrilus anxius (Coleoptera: Buprestidae)

A microsporidium was isolated from the bronze birch borer, Agrilus anxius Gory (Coleoptera: Buprestidae), collected near Sudbury and Sault Ste Marie, Canada. Light and electron microscopic investigations showed that gross pathology and ultrastructure of the investigated Cystosporogenes species was similar to those characterized and described for other Cystosporogenes species. Small subunit rRNA gene sequence data and comparative phylogenetic analysis confirmed that the microsporidian species from A. anxius is most closely related to the genus Cystosporogenes clade of microsporidia. Infection average in the Sudbury and Sault Ste Marie beetle populations was >80% and relatively stable in 2006-2007 but declined in 2008. Field prevalence of the A. anxius isolate, mechanisms that may potentially be involved in its horizontal (autoinfection) and vertical (transovarial) transmission, and disease dynamics are discussed. The congeneric relationship between Agrilus planipennis and A. anxius makes it imperative to study the virulence of this Cystosporogenes species in A. planipennis.