Snow algae of the Windmill Islands, continental Antarctica: Chlorosarcina antarctica comb. nov. (Chlorophyceae, Chlorophyta) from pink snow, with discussion of Chlorosarcina and allied genera

Abstract

A red snow alga previously identified as Chlamydomonas antarcticus Wille was found to be the spores of Chlorosarcina antarctica (Wille) H.U. Ling comb. nov. The spores were spherical, very variable in size, and individually enveloped in mucilage. Each spore released a mass of daughter cells, which divided in three planes to form cubical, loose aggregates of green cells embedded in mucilage. The spherical to broadly oval cells had a mucilaginous cell wall and a cup-shaped chloroplast, which lacked pyrenoids. The cells sometimes produced biflagellate, naked zoospores without stigmata. The flagellar basal apparatus of the zoospores had a clockwise orientation. Dichotomously branched, mucilaginous stalks characteristic of Hormotila were produced in old cultures. The species was often found in semipermanent snow drifts on the shores of small bays, and records to date show it to be restricted to the Southern Hemisphere. Algal snow samples had pH of 6.3–6.9 and conductivity of 39–44 μS cm−1. Two strains were isolated and are currently maintained at the Australian Antarctic Division. These did not grow above 10°C. The species was compared with a strain of Desmotetra stigmatica and with Chlorosarcina strain T105. The results confirm the validity of the genus Chlorosarcina and its retention in the Chlorophyceae.