Morphological and Genetic Variation in the Cosmopolitan Snow Alga Chloromonas nivalis (Volvocales, Chlorophyta) from Japanese Mountainous Area

Abstract

Summary Mature zygotes of the cosmopolitan snow alga Chloromonas nivalis (Chodat) Hoham & Mullet [ϭScotiella nivalis (Chodat) Fritsch] collected from Mt. Gassan, Yamagata Prefecture, were examined by scanning electron microscopy (SEM) and single-cell sequencing of the large subunit of Rubisco (rbcL) genes. The present SEM demonstrated that Japanese samples have at least two types of flanges on the zygote wall (straight and sigmate). Although these types fell within the morphological variability of C. nivalis as reported previously, at least two types of rbcL (large subunit of Rubisco) gene sequences were detected by using the single-cell sequencing. Although the information of the rbcL genes were limited (340-400 bp), the present phylogenetic analyses revealed that these two Japanese types and C. nivalis originating from North America belong to the lineage composed of Chloromonas snow taxa. Thus, C. nivalis might involve multiple cryptic species of Chloromonas. Further ovservations of other stages of life cycle and more detailed phylogenetic analysis are needed to reveal the correct taxonomic identifications of C. nivalis.

Temporal changes in snow algal abundance on surface snow in Tohkamachi, Japan

“…nivalis, which are commonly reported from snowfields in Japan, as well as worldwide (Muramoto et al, 2008). The shape, size, and pigmentation of the type A algal cells corresponded with those of the cysts of Cr.…”

“…Two morphological types of snow algae were observed in the site, and they are likely to be Cr. nivalis, which is a common species on seasonal snow surfaces in Japan, as well as worldwide (Muramoto et al, 2008). The timing of the algal appearance on the snow surface varied from February 4 to February 25 in the four winters.…”

“…Cr. nivalis is a species characterized by a wide tolerance to environmental factors, growing both at shade (spruce or broadleaf trees) and open exposure sites (Komárek and Nedbalová, 2007;Nedbalová et al, 2008), and can be seen on snowfields in Japanese mountains during the melting season (Muramoto et al, 2008). Most commonly, the immotile mature cysts populate the snow surface, and they have in abundance the secondary carotenoid astaxanthin that causes the orange color of the cytoplasmic lipid bodies (Remias et al, 2010), which could be seen in type A cells.…”

Taxonomic revision of Chloromonas nivalis (Volvocales, Chlorophyceae) strains, with the new description of two snow-inhabiting Chloromonas species

“…nivalis strain UTEX SNO71 and field-collected C . nivalis zygote specimens examined in previous studies [ 19 , 20 , 41 ] was performed by single-gene phylogenetic analyses using 18S rDNA and rbc L sequences ( S4 and S5 Figs). Both trees reconstructed the monophyletic groups B–D which were robustly resolved in the multigene phylogenetic tree ( Fig 4 ), but statistical support values for monophyly were lower.…”

“…In addition, we set three partitions (first, second, and third codon positions) for BI and ML analysis of rbc L gene sequences according to a previous study [ 4 ]. Additional operational taxonomic units were selected from previous studies [ 19 , 20 , 41 ] and shown in S3 Table .…”