TWO SNOW SPECIES OF THE QUADRIFLAGELLATE GREEN ALGACHLAINOMONAS(CHLOROPHYTA, VOLVOCALES): ULTRASTRUCTURE AND PHYLOGENETIC POSITION WITHIN THE CHLOROMONAS CLADE¹

Abstract

The quadriflagellate snow alga Chlainomonas Christen, distributed in New Zealand and North America, has several unusual structural attributes. A process assumed to be cytokinesis involves extrusion of protoplasm from the parent through a narrow canal, C. kolii (J. T. Hardy et Curl) Hoham produces a net-like outer envelope rather than a cell wall, and the flagellar basal apparatus of Chlainomonas consists of two semi-independent pairs of basal bodies. Structural connections between basal body pairs appear minimal, but a connecting system different from that observed in other genera exists within each pair. Phylogenetic analysis using rbcL sequences places Chlainomonas in the Chloromonas clade, other known members of which are all biflagellate. Chlainomonas is split into two robust lineages, with New Zealand collections sharing an origin with northern North American collections. Although the quadriflagellate condition is regarded as ancestral in the Chlorophyceae, we speculate-based on ultrastructural and molecular data presented here-that Chlainomonas represents a derived form that has arisen from fusion of two ancestral biflagellate cells. Other explanations (for example, that Chlainomonas represents a diploid form of a biflagellate species) are remotely possible but are presently at odds with extensive observations of field material. Improvements in techniques for experimental manipulation of these sensitive cryophiles will be required to fully characterize their structure and progress our understanding of their biology.

Re-examination of the snow algal speciesChloromonas miwae(Fukushima) Muramotoet al., comb. nov. (Volvocales, Chlorophyceae) from Japan, based on molecular phylogeny and cultured material

“…However, resolution of a clade corresponding to subclade 2 of Clade A (Hoham et al, 2002) was low (only 55-78% bootstrap values in MP and ME analyses). The quadriflagellate genus Chlainomonas was included in subclade 2 by Novis et al (2008). Our Japanese samples/strains and four North American Chloromonas species (Cr.…”

A taxonomic revision of Chloromonas reticulata (Volvocales, Chlorophyceae), the type species of the genus Chloromonas, based on multigene phylogeny and comparative light and electron microscopy

“…reticulata (Goroschankin) Gobi, belongs to the Chloromonas clade, all species within this clade were classified as Chloromonas based on their characteristic chloroplast morphology under LM (Prö schold et al 2001). However, recent studies have demonstrated that the Chloromonas lineage, Chloromonadinia (Nakada et al 2008a), includes two morphologically different genera, Chlainomonas Christen, which has four flagella and a swollen or gelatinous cell wall separated from the protoplast (Novis et al 2008), and Gloeomonas G.A. Klebs, which has two separated flagellar bases .…”

Cryoseston of the Pirin Mountains, Bulgaria

“…C. kolii was described as a snow alga by HOHAM (1974a), who re-arranged Trachelomonas kolii (Euglenales) into Chlorophyta, as Chlainomonas kolii. This same alga was described in snow samples from Canada, in the NW Pacific Mountains of the USA, and in Mt Philistine, New Zealand (NOVIS 2002, NOVIS et al 2008. Chlainomonas rubra (HOHAM 1974b) was identified in snow in Tirole, N. Island of New Zealand, the Pacific Northwest USA, Wenatchee Natl For., Washington, and Mt.…”

“…Maybe Chlainomonas was derived from the fusion of biflagellate cells or is a diploid component of a biflagellate phase (sexual reproduction was not seen). The flagellar basal apparatus was also organized into two distinct pairs of basal bodies that lack connections (NOVIS et al 2008). The alga is very sensitive to temperature, and can only live at 0-4°C (HOHAM 1975).…”

“…Seymour Park, Brit. Columbia, Canada (NOVIS et al 2008). It represents a new genus and species for the Bulgarian algal database, and this is only the second documented record in Europe.…”