Amendments to the description of Chloromonas actinochloris (Chlorophyta) inferred from the study of the South Siberian finding

Chlamydomonas-like green microalgae are unicellular biflagellate organisms from the order Volvocales, which are widely distributed in terrestrial ecosystems. Recent studies have shown that they belong to different phylogenetic lineages. The exact establishment of the taxonomic affiliation of these representatives is based on integrative approach, including multigene phylogeny along with light and electron microscopy, which also allows us to get the most accurate information about their biogeography. In this study, we examined the terrestrial green Chlamydomonas-like microalga, isolated from soil of the South-Eastern Altai Mountains in Russia. Based on molecular data of the nuclear 18S and plastid rbcL gene, we refer this alga to Chloromonas actinochloris within a robust clade of the genus Chloromonas, the phylogroup Chloromonadinia. This species was described from North America (USA). It is the first discovery of C. actinochloris in the mountains of Southern Siberia, as well as the first record of the species in Russia confirmed by molecular phylogeny and microscopy methods. The description of C. actinochloris, information on its biology and geography was supplemented. It is generally accepted that the phylogenetic clade including C. actinochloris should be revised and reassigned to a new genus soon. Our study shows that vegetative cells of Chloromonadinia algae can have ornamented cell wall that was mainly known for resting cells (cysts/zygotes) in a number of chlamydomonads, more rarely for vegetative cells. The structures on the wall of vegetative cells of Chlamydomonaslike microalgae can serve as an additional diagnostic criterion.