Abstract
Prasinophytes are a paraphyletic group of nine lineages of green microalgae that are currently classified either at the class or order level or as clades without formal taxonomic description. Prasinophyte clade VII comprises picoplanktonic algae that are important components of marine phytoplankton communities, particularly in moderately oligotrophic waters. Despite first being cultured in the 1960s, this clade has yet to be formally described. Previous phylogenetic analyses using the 18S rRNA gene divided prasinophyte clade VII into three lineages, termed A, B and C, the latter formed by a single species, Picocystis salinarum, that to date has only been found in saline lakes. Strains from lineages A and B cannot be distinguished by light microscopy and have very similar photosynthetic pigment profiles corresponding to the prasino-2A pigment group. We obtained phenotypic and genetic data on a large set of prasinophyte clade VII culture strains that allowed us to clarify the taxonomy of this important marine group. We describe two novel classes, the Picocystophyceae and the Chloropicophyceae, the latter containing two novel genera, Chloropicon and Chloroparvula, and eight new species of marine picoplanktonic green algae.
Highlights
Prasinophytes are a paraphyletic group of nine lineages of green microalgae that are currently classified either at the class or order level or as clades without formal taxonomic description
Analysis of morphology and genome size of members of prasinophyte clade VII reveals few discriminating characters between clades. Large genetic divergences, such as those observed between clades and lineages of prasinophyte clade VII9, are commonly associated with morphological variations
A large set of culture strains of members of prasinophyte clade VII (Table 1) were grown under identical culture conditions and morphological and genome size analyses were performed to determine whether patterns characteristic of lineages or clades exist
Summary
The cells were post-fixed in a mixture of 1% osmium tetroxide and 1% potassium ferricyanide in 0.1 M sodium cacodylate (final concentrations) for 2 hours at 4 °C and subsequently rinsed three times (10 min each) in 0.1 M cacodylate and twice in MilliQ water (5 min each). Samples were dehydrated in an aqueous ethanol series (10 min in 30%, 50%, 70%, 90%, 96%, and four times in 100%, 5 min each) and rinsed twice with propylene oxide (5 min each). Three subsequent rinses in 0.1 M cacodylate were performed (5 min each) and the cells were dehydrated in an aqueous ethanol series (10 min in 70%, 90%, 96% and three changes in 100%, 10 min each). An additional protocol was followed for some of the samples; a drop of culture
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
