Two new fungal parasites of bdelloid rotifers

Abstract

Haptoglossa humicola (Oomycetes) and Tolypocladium trigonosporum (Hyphomycetes) are described as new endoparasites attacking rotifers, belonging to the genera Adineta and Philodina, in soil. In H. humicola the laterally biflagellate zoospores produce spherical cysts each of which then germinates to form a specialized injection cell. The host is attacked by means of rapid injection of a sporidium through the cuticle. Each sporidium produces a thallus inside the host which at maturity functions as a zoosporangium. In T. trigonosporum, after infection, a network of curved anastomosing fertile hyphae produces a loose shell around the encysted host. Conidia are not produced under water, but in air these fertile hyphae give rise to solitary or clustered phialides and triangulate conidia.