Phylogeny and morphology of genus Nephrocytium (Sphaeropleales, Chlorophyceae, Chlorophyta) from China

Abstract

The genus Nephrocytium Nägeli is a common member of phytoplankton communities that has a distinctive morphology. Its taxonomic position is traditionally considered to be within the family Oocystaceae (Trebouxiophyceae). However, research on its ultrastructure is rare, and the phylogenetic position has not yet been determined. In this study, two strains of Nephrocytium, N. agardhianum Nägeli and N. limneticum (G.M.Smith) G.M.Smith, were identified and successfully cultured in the laboratory. Morphological inspection by light and electron microscopy and molecular phylogenetic analyses were performed to explore the taxonomic position. Ultrastructure implied a likely irregular network of dense and fine ribs on the surface of the daughter cell wall that resembled that of the genus Chromochloris Kol & Chodat (Chromochloridaceae). Phylogenetic analyses revealed that Nephrocytium formed an independent lineage in the order Sphaeropleales (Chlorophyceae) with high support values and a close phylogenetic relationship with Chromochloris. Based on combined morphological, ultrastructural and phylogenetic data, we propose a re-classification of Nephrocytium into Sphaeropleales, sharing a close relationship with Chromochloris.

Fatty Acids, Hydrocarbons and Terpenes of Nannochloropsis and Nannochloris Isolates with Potential for Biofuel Production

“…Marine microalgae were collected from the water column at three different sites in Progreso, Yucatan, located at 21 • 50.07 W. Samples were collected at three different depths (0.0, 0.5 and 1 m) from water bodies during the mornings of May 2014 using a Van Dorn bottle (1120-G45, Wildco, Yulee, FL, USA). The pH, temperature and salinity values (Extech Stick EC500, Extech instruments, Boston, MA, USA) were registered [19].…”

“…However, there are many morphologic details to reject this possibility. Oocystaceae (Trebouxiophyceae) have a characteristic cell wall substructure that is composed of several cellulose layers with perpendicular fibril orientations [50]. In fact, since the work of Komárek (1979) the definition of the family has been based upon the ultrastructure of the multilayered cell wall [51].…”

“…several cellulose layers with perpendicular fibril orientations [50]. In fact, since the work of Komárek (1979) the definition of the family has been based upon the ultrastructure of the multilayered cell wall [51].…”

Revised phylogenetic position of Nephrocytium Nägeli (Sphaeropleales, Chlorophyceae), with the description of Nephrocytiaceae fam. nov. and Nephrocytium vieirae sp. nov.

“…Placement of Nephrocytium by molecular phylogeny. -A previous study analyzed several strains of Nephrocytium and provisionally designated the genus as an incertae sedis lineage within the Sphaeropleales (Liu & al., 2017;Štenclová & al., 2017). However, no formal taxonomic conclusions were proposed.…”

“…Despite the phylogenetic proximity, Chromochloris presents significant morphological differences from Nephrocytium: absence of a pyrenoid, no colony formation, reproduction also by zoospores, mature cells multinucleated and with multiple chloroplasts, and accumulation of carotenoids . Furthermore, Chromochloris zofingiensis has cell wall surfaces with a network of irregular ribs or wrinkles (Kalina & Punc ˇochářová, 1987;Liu & al., 2017), which differs from the smooth surface of Nephrocytium (Edelstein & Prescott, 1964;Komárek & Fott, 1983) (Fig. 2G-I).…”