''Stephanosphaera'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

green algae The green algae (: green alga) are a group of chlorophyll-containing autotrophic eukaryotes consisting of the phylum Prasinodermophyta and its unnamed sister group that contains the Chlorophyta and Charophyta/ Streptophyta. The land plants ...

in the family

Haematococcaceae Haematococcaceae is a family of green algae in the order Chlamydomonadales. It consists of freshwater algae such as '' Chlorogonium'', '' Haematococcus'' and '' Stephanosphaera''. Members of the family Haematococcaceae have cells with are spindl ...

, containing the single species ''Stephanosphaera pluvialis''. It forms colonies of flagellated cells. Although it was once placed in the family

Volvocaceae The Volvocaceae are a family of unicellular or colonial biflagellates algae, including the typical genus ''Volvox'', and are collectively known as the volvocine algae. The family was named by Ehrenberg in 1834, and it is known in older classifi ...

, it is not closely related to them; its sister is the unicellular genus '' Balticola''. The name comes from the Greek roots ''stephanos'', meaning "crown", and ''sphaira'', meaning "ball".

Description

''Stephanosphaera pluvialis'' forms colonies of four or eight cells, arranged in a ring and surrounded by a spherical matrix. Each cell is elongated, irregularly shaped with several protrusions that join the cells together. Cells contain several

contractile vacuole A contractile vacuole (CV) is a sub-cellular structure (organelle) involved in osmoregulation. It is found predominantly in protists, including unicellular algae. It was previously known as pulsatile or pulsating vacuole. Overview The contrac ...

s, a rounded stigma, and a single large parietal

chloroplast A chloroplast () is a type of membrane-bound organelle, organelle known as a plastid that conducts photosynthesis mostly in plant cell, plant and algae, algal cells. Chloroplasts have a high concentration of chlorophyll pigments which captur ...

with usually two

pyrenoid Pyrenoids are sub-cellular phase-separated micro-compartments found in chloroplasts of many algae,Giordano, M., Beardall, J., & Raven, J. A. (2005). CO2 concentrating mechanisms in algae: mechanisms, environmental modulation, and evolution. ''An ...

s. Cells have two

flagella A flagellum (; : flagella) (Latin for 'whip' or 'scourge') is a hair-like appendage that protrudes from certain plant and animal sperm cells, from fungal spores ( zoospores), and from a wide range of microorganisms to provide motility. Many pr ...

of equal length.

Reproduction

''Stephanosphaera pluvialis'' reproduces both asexually and sexually. Asexual reproduction occurs by autocolony formation: a cell divides until it becomes like a miniature version of the existing colony, and the new colony is released from the cell. Sexual reproduction is done with gametes, which are

isogamous Isogamy is a form of sexual reproduction that involves gametes of the same morphology (indistinguishable in shape and size), and is found in most unicellular eukaryotes. Because both gametes look alike, they generally cannot be classified as ma ...

Distribution

''Stephanosphaera pluvialis'' is found in

freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. The term excludes seawater and brackish water, but it does include non-salty mi ...

habitats. It tends to occur in

rainwater Rain is a form of precipitation where water droplets that have condensed from atmospheric water vapor fall under gravity. Rain is a major component of the water cycle and is responsible for depositing most of the fresh water on the Eart ...

puddle A puddle is a very small accumulation of liquid, usually water, on a surface. It can form either by pooling in a depression on the surface, or by surface tension upon a flat surface. Puddles are often characterized by murky water or mud due to t ...

s on non-basic rocks, more rarely in lakes. It is rare.

References

{{Taxonbar, from1=Q7608479, from2=Q69644084 Chlamydomonadales genera Chlamydomonadales Monotypic algae genera