Nephroselmis excentrica sp. nov. (Nephroselmidophyceae, Chlorophyta) from Okinawa-jima, Japan

Abstract

Faria D.G., Kato A. and Suda S. 2012. Nephroselmis excentrica sp. nov. (Nephroselmidophyceae, Chlorophyta) from Okinawa-jima, Japan. Phycologia 50: 271–282. DOI: 10.2216/10-74.1Nephroselmis excentrica Faria et Suda sp. nov. is described on the basis of light and electron microscopy. Phylogenetic analyses based on 18S rDNA sequences of N. excentrica were also conducted. Strains of N. excentrica were isolated from coastal sand samples collected from two localities of Okinawa-jima, Japan. The cells are remarkably right-left flattened and appear eccentrically ovoid or elliptical when viewed from their right or left side. A single, parietal, olive-yellow chloroplast contains one conspicuous large eyespot in its anterior ventral edge near the short flagellum base. The eyespot globules are arranged in two layers. A single conspicuous pyrenoid is surrounded by a single starch sheath, which is dorsally situated. The pyrenoid matrix is traversed by sheet-like thylakoid protuberances. The alga possesses five types of body scales, three types of flagellar scales and two types of hair scales. The cell morphology, pyrenoid structure, scale types and cell size are distinctive from previously described Nephroselmis species, and its eccentric cell shape led us to name this newly proposed species ‘excentrica’. 18S rDNA sequences reveal that N. excentrica forms a monophyletic clade with N. olivacea and N. viridis, but the clade is not supported by high bootstrap values.