''Gonium pectorale'' is a species of

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

Goniaceae Goniaceae is a family of algae in the order Chlamydomonadales, that includes the genera '' Astrephomene'' and '' Gonium''. Members of the Goniaceae are distinguished from those of the Volvocaceae by having each cell surrounded by a tripartite bo ...

. It is a freshwater species with a

cosmopolitan distribution In biogeography, a cosmopolitan distribution is the range of a taxon that extends across most or all of the surface of the Earth, in appropriate habitats; most cosmopolitan species are known to be highly adaptable to a range of climatic and en ...

. ''Gonium pectorale'' is the

type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...

of the genus ''Gonium'', and is the most common species in the genus. It is a

model organism A model organism is a non-human species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the model organism will provide insight into the workings of other organisms. Mo ...

for studying the evolution of

multicellularity A multicellular organism is an organism that consists of more than one cell, unlike unicellular organisms. All species of animals, land plants and most fungi are multicellular, as are many algae, whereas a few organisms are partially uni- and pa ...

Description

''Gonium pectorale'' is a colonial, flagellate organism 70–100 μm wide, with 16 (sometimes 8 or 32) cells. In its usual form, it consists of four cells in the center and 12 cells in the periphery, with flagella pointing outward. Cells are nearly spherical or weakly pear-shaped, and are up to 18 μm wide. They contain a single cup-shaped

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 one or two basal

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 ...

and an eyespot in the anterior. Each cell has two, equal

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 ...

. ''Gonium pectorale'' is similar to other ''Gonium'' species, especially in its 16-celled form. Eight-celled colonies of ''Gonium pectorale'' are almost always in a zig-zag arrangement of two cells per row. The similar species '' Gonium viridistellatum'' has eight-celled colonies consisting of seven peripheral cells and one central cell, while '' Gonium maiaprilis'' has eight-celled colonies in a variety of different configurations.

Varieties

''Gonium pectorale'' is a very variable species. Within ''G. pectorale'', two varieties have been described by Mary Pocock. Compared to the typical variety ''pectorale'', variety ''praecox'' has smaller, usually pale green colonies with elongated cells. The term ''praecox'' refers to the early (precocious) development of daughter colonies.

Reproduction

''Gonium pectorale'' reproduces both asexually and sexually. In ''Gonium pectorale'', the protoplasm of a cell divides successively until it forms a new, miniature colony. Sexual reproduction is

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 ...

; each cell in a colony becomes a

gamete A gamete ( ) is a Ploidy#Haploid and monoploid, haploid cell that fuses with another haploid cell during fertilization in organisms that Sexual reproduction, reproduce sexually. Gametes are an organism's reproductive cells, also referred to as s ...

. The gametes contact each other by their flagella, and form a cytoplasmic bridge until they fuse, becoming a zygote. The zygote has a thick, smooth

cell wall A cell wall is a structural layer that surrounds some Cell type, cell types, found immediately outside the cell membrane. It can be tough, flexible, and sometimes rigid. Primarily, it provides the cell with structural support, shape, protection, ...

. Upon germination, the zygote forms four cells which undergo successive divisions, eventually becoming a 16-celled colony. Within ''Gonium pectorale'', there are two clades that appear to be

reproductively isolated The mechanisms of reproductive isolation are a collection of evolutionary mechanisms, behaviors and physiological processes critical for speciation. They prevent members of different species from producing offspring, or ensure that any offsprin ...

. Clade A is cosmopolitan, whereas Clade B is restricted to the Southern Hemisphere.

Habitat

''Gonium pectorale'' is found in freshwater habitats, particularly nutrient-rich lakes, rivers, ditches and ponds. It is most common in spring.

References

{{Taxonbar, from=Q63171213 Chlamydomonadales Chlorophyta species