LAUSR

ABSTRACT A new species in the genus Prasionema (Prasiolales, Trebouxiophyceae) is described from Campbell Island, in the New Zealand subantarctic region, the first record of this genus in the southern hemisphere. Prasionema heeschiae sp. nov. is filamentous, uni- to predominantly biseriate, with disc-shaped cells, and an axial plastid with a central pyrenoid. It is anchored by an enlarged pigmented basal cell. There is evidence of reproduction by both spores and fragmentation. This species was found growing on a timber wharf above the high tide level. The only other species in the genus, P. payeri Heesch, M.Pazoutová & Rindi, was described from Spitzbergen growing on soil in a high nutrient environment. The bipolar distribution of Prasionema is discussed. Based on phylogenetic analyses that included sequence data from holotype material of southern filamentous Prasiolales, we reduce Rosenvingiella australis to synonymy with R. tasmanica.