Taxonomy of Nephroselmis viridis sp. nov. (Nephroselmidophyceae, Chlorophyta), a sister marine species to freshwater N. olivacea

Abstract

The genus Nephroselmis (Nephroselmidophyceae), which had been placed in the Prasinophyceae, is one of the primitive green flagellates that are important to our understanding of the early evolution of green plants. We studied a new species of Nephroselmis isolated from Japan, Fiji and South Africa. This species has been known for a long time as undescribed species 'N. viridis.' N. viridis possesses some ultrastructural characters shared with only the freshwater type species N. olivacea, including a disc-like structure beneath the pyrenoid and bipolar spiny body scales with 1-5-8-5-1 spines. Molecular phylogenetic analysis based on 18S rDNA also supports a sister relationship between N. viridis and N. olivacea. However, N. viridis is distinguishable from N. olivacea by the shape of its starch sheath, its scales, its pigment composition and its habitat. In this paper, we designate the formal description of N. viridis sp. nov. We also describe variability in the 18S rDNA introns of various N. viridis strains. This detailed study of N. viridis provides some insights into the evolution of Nephroselmis.

Nephroselmis viridis (Nephroselmidophyceae, Chlorophyta), a new record for the Atlantic Ocean based on molecular phylogeny and ultrastructure

“…The cell measures of Nephroselmis viridis from the Atlantic Ocean, such as width and length of cell body and flagella, are exactly the same of the type described in Yamaguchi et al (2011). Ultrastructural features observed also endorse the identification, such as the chloroplast form and location, the pyrenoid cup shaped and its starch sheath, the thylakoid sheets penetrating into the pyrenoid, the disk like structure, and the positions of the reticulate mitochondrion, nucleus, and Golgi apparatus.…”

“…Ultrastructural features observed also endorse the identification, such as the chloroplast form and location, the pyrenoid cup shaped and its starch sheath, the thylakoid sheets penetrating into the pyrenoid, the disk like structure, and the positions of the reticulate mitochondrion, nucleus, and Golgi apparatus. The shape and location of these organelles are the same as observed by Yamaguchi et al (2011). However, the color of the cells and culture are different from the species description.…”

“…Four sequences of phylogenetically close species were used to root the tree (Pyramimonas aurea, Pseudoscourfieldia marina, and Pycnococcus provasolii). These sequences were chosen based on previous studies of Nephroselmis phylogeny (Faria et al 2012;Faria et al 2011;Nakayama et al 2007;Yamaguchi et al 2011). Introns were removed from the data.…”

“…The nuclear gene coding for the ribosomal small subunit RNA (18S rDNA) is the most widely used molecular marker for this group (Bell 2008;Faria et al 2012;Faria et al 2011;Nakayama et al 2007;Nakayama et al 1998;Yamaguchi et al 2011). However, sequences for just nine species of this molecular marker are available in Genbank, representing less than 65% of the genus biodiversity.…”

“…Nephroselmis viridis Inouye, Pienaar, Suda & Chihara was described in 2011 and strains were isolated from marine waters of Fiji, Japan and South Africa, in the Pacific and Indic Oceans (Yamaguchi et al 2011). In the Atlantic Ocean, just five Nephroselmis species were recorded previously, vis., N. discoidea Skuja (Menezes and Bicudo 2008), N. fissa (Lackey 1940), N. minuta (N.Carter) Butcher (Butcher 1959;Domingos and Menezes 1998), N. pyriformis (N.Carter) Ettl (Bergesch et al 2008;Moestrup 1983;Steinkotter et al 1994), and N. rotunda (N.Carter) Fott (Bell 2008;Butcher 1959).…”