Hortaea, a new genus to accommodate Cladosporium werneckii.

Abstract

A new genus, Hortaea Nishimura et Miyaji, is proposed to accommodate Cladosporium werneckii, the etiological agent of a superficial mycotic infection, tinea nigra, and Hortaea werneckii (Horta) Nishimura et Miyaji comb. nov. is provided.The fungus is characterized by a unique sympodial conidiogenesis accompanying an annellidic one, which has been observed firstly using a scanning electron microscope as follows.Conidiogenous loci arise from ampullaceous cells formed laterally or terminally on hyphae, lateral branches and projections on hyphae, or directly from the lateral walls of hyphae. These loci elongate and swell in accordance with the production of solitary, terminal conidia, and become thick cylindrical, obclavate or truncate rachises. Bud scars are found on the surface of the rachises, but denticles are absent. Round scars are observed in a few conidiogenous cells on the rachises, but most of the conidiogenous cells show remnants of scars shaped like sickles, half moons or scales. Regardless of the bud scar shapes, a spiral can be drawn on a rachis by tracing the centers of the scars. Namely, the conidiogenous cells are sympodulae because the bud scars are arranged on them sympodially. Such sympodial conidiogenesis is also found in most of the yeast-like conidiogenous cells.Furthermore, there are a few conidiogenous cells with annellatons, which are irregular in comparison with those of E. dermatitidis or E. jeanselmei.These results indicate that H. werneckii is definitely different from the other species of the genus Exophiala and other sympodial dematiaceous fungi.