Actinotaenium

Actinotaenium is a genus of green algae, specifically of the Desmidiaceae. It is a freshwater genus, typically found in the benthos of acidic, oligotrophic lakes or Sphagnum bogs. It has a cosmopolitan distribution. Actinotaenium consists of solitary cells with two halves, called semicells; cells have a central constriction called an isthmus where the two semicells are joined. Cells are globose, ovoid, cylindrical or pyramidal when viewed from the side, but circular when viewed from the poles. The cell walls are covered in ornamentation such as fine pores, punctae or scrobiculae (pits); the distribution of ornamentation varies by species. Each semicell has a single chloroplast, which is stellate in cross-section and often with complex lobes. Asexual reproduction occurs by vegetative cell division, similar to that of Cosmarium. Sexual reproduction is by conjugation, with zygotes forming between cells. Mature zygospores are quadrate, or globose with smooth walls, protuberances or spines.......read more on Wikipedia.