Retrostium amphiroae gen. et sp. nov. inhabiting a marine red alga, Amphiroa zonata

Abstract

Retrostium amphiroae gen. et sp. nov. (Spathulosporaceae), a fungus inhabiting Amphiroa zonata (marine Rhodophyta) in coastal habitats in Japan, is described. This fungus produces mononematous spermatiophores with penicillate phialides and trichogynes at the edge of ascomata on the surface of the host alga. The ostiolar canal of the ascoma has a tube-like projection extending into the ascomatal cavity, a feature that is shared only with some species of Chadefaudia and Haloguignardia. Comparison of the new fungus with Spathulospora and Hispidicarpomyces species (Spathulosporales) in morphology, life history and host suggests that it has mixed characteristics of the two genera. The new fungus is inferred to be a phylogenetic link between the spathulosporalean fungi and other algae-inhabiting marine fungi in the genera Chadefaudia and Haloguignardia.

Key Words:

• algal parasite
• Ascomycetes
• marine fungi
• Spathulosporaceae
• Spathulosporales
• systematics