{{Short description|Genus of algae}} {{Automatic taxobox | image = Halosphaera viridis.jpg | image_caption = ''Halosphaera viridis'' | taxon = Halosphaera | authority = Schmitz 1879 | type_species = Halosphaera viridis | type_species_authority = Schmitz 1879<ref name=AlgaeBase>{{AlgaeBase genus | id=44991 | title=''Halosphaera'' F.Schmitz, 1878 | access-date=2026-05-09 }}</ref> | subdivision_ranks = Species | subdivision = * ''H. minor'' <small>Ostenfeld</small> * ''H. ovata'' <small>Schütt</small> * ''H. parkeae'' <small>Boalch & Mommaerts</small> * ''H. russellii'' <small>Parke</small> * ''H. viridis'' <small>Schmitz 1878</small> }}

'''''Halosphaera''''' is a genus of green algae in the order Pyramimonadales.<ref>See the NCBI [https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info&id=81842 webpage on Halosphaera]. Data extracted from the {{cite web | url=https://ftp.ncbi.nih.gov/pub/taxonomy/ | title=NCBI taxonomy resources | publisher=National Center for Biotechnology Information | access-date=2007-03-19}}</ref> ''Halosphaera'' is widely distributed in the plankton of oceans, and is found in both hemispheres.<ref name=AlgaeBase/>

''Halosphaera'' consists of two life stages: a non-motile coccoid stage, called the phycoma stage ({{pl.|phycomata}}), and a flagellated stage. The phycoma is spherical, up to 800 &mu;m in diameter, with two layers of cell walls: The inner wall is pectin-like, while the outer wall is tough and sporopollenin-like. Mature phycomata contain a single nucleus and several numerous chloroplasts, in most species with pyrenoids.<ref name=AlgaeBase/>

''Pterosperma'' divides asexually in the phycoma stage, forming a large number of flagellate swarmer cells. Swarmers have four long flagella which arise from a pit in the anterior surrounded by four lobes. Each contain a single parietal chloroplast with two to four pyrenoids, and an eyespot. The cell body is covered with several types organic scales, and the flagella are also covered with multiple layers of cells. Flagellate cells can also divide by fission.<ref name=AlgaeBase/>

==References== {{Reflist|1}}

{{Taxonbar|from=Q5643460}}

Category:Chlorophyta genera Category:Pyramimonadophyceae

{{green algae-stub}}