Placoma regulare sp. nov. (Entophysalidaceae, Cyanobacteria) from New Zealand streams

Abstract

An unusual colonial chroococcalean alga (Cyanobacteria) is described from freshwater streams using light and electron microscopy. Young, initially solid colonies mature to become hollow, suggesting that it is a member of the poorly known genus Placoma. Placoma regulare sp. nov. is proposed, due to the characteristic cubical to more or less pseudofilamentous cell arrangement. Other notable characteristics of this new species include a tendency for cells to increase greatly in size, and to become markedly vacuolate with increasing distance below the colony surface. It is locally abundant, attached to rocks and bryophytes in fast-flowing streams at altitudes up to 1036 m in mountain regions of the South Island of New Zealand.