''Pandorina'' is a genus 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 Volvocaceae. It is a common
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 ...
genus, and has 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 ...
.
[ Along with other algae such as '' Volvox'', '' Eudorina'' and '']Chlamydomonas
''Chlamydomonas'' ( ) is a genus of green algae consisting of about 150 species of unicellular organism, unicellular flagellates, found in stagnant water and on damp soil, in freshwater, seawater, and even in snow as "snow algae". ''Chlamydom ...
'', 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 origins and evolution of multicellularity.
Description
''Pandorina'' is composed of 8, 16, or sometimes 32 cells, held together at their bases to form a globular or ellipsoidal colony surrounded by mucilage
Mucilage is a thick gluey substance produced by nearly all plants and some microorganisms. These microorganisms include protists which use it for their locomotion, with the direction of their movement always opposite to that of the secretion of ...
. The cells are ovoid or slightly narrowed at one end to appear keystone- or pear
Pears are fruits produced and consumed around the world, growing on a tree and harvested in late summer into mid-autumn. The pear tree and shrub are a species of genus ''Pyrus'' , in the Family (biology), family Rosaceae, bearing the Pome, po ...
-shaped. Each cell has 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 ...
with two contractile vacuole
A vacuole () is a membrane-bound organelle which is present in Plant cell, plant and Fungus, fungal Cell (biology), cells and some protist, animal, and bacterial cells. Vacuoles are essentially enclosed compartments which are filled with water ...
s at its base, an eyespot, and a large 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 at least one 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 ...
.[ The colonies co-ordinate their flagellar movement to create a rolling, swimming motion. ''Pandorina'' shows the beginnings of the colony polarity and differentiation seen in '' Volvox,'' with anterior cells having larger eyespots.
]Asexual reproduction
Asexual reproduction is a type of reproduction that does not involve the fusion of gametes or change in the number of chromosomes. The offspring that arise by asexual reproduction from either unicellular or multicellular organisms inherit the f ...
is by simultaneous division of all cells of the colony to form autocolonies that are liberated by a gelatinization of the colonial envelope. Sexual reproduction
Sexual reproduction is a type of reproduction that involves a complex life cycle in which a gamete ( haploid reproductive cells, such as a sperm or egg cell) with a single set of chromosomes combines with another gamete to produce a zygote tha ...
occurs by division of each cell of the colony into 16-32 zoogametes.[Smith, GM. ''Phytoplankton of Inland Lakes of Wisconsin'', Part I, Wisconsin Geological and Natural History Survey, Madison, WI. (1920).] Sexual reproduction is isogamous.[
]
Taxonomy
The taxonomy of ''Pandorina'' and '' Eudorina'' have been confused because the original description was insufficient to distinguish the two genera.[ In addition, some species appear to be intermediate in morphology between the two, and have at times been considered part of either genus, such as ''Pandorina/Eudorina charkowiensis''. Currently, these intermediate taxa are placed in two genera, '' Colemanosphaera'' and '' Yamagishiella''. Therefore, the genera are separated as follows:][ no cellular envelope around each individual cell.][
* '' Colemanosphaera'': two or three contractile vacuoles at the base of the flagella; multiple pyrenoids in a mature cell; sexual reproduction anisogamous, with fertilization happening outside of the female spheroid; cellular envelope around each individual cell.][ cellular envelope around each individual cell.][
Molecular sequencing has shown that ''Pandorina'' is ]paraphyletic
Paraphyly is a taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping is said to be paraphyletic ''with respect to'' the excluded subgroups. In co ...
with respect to '' Volvulina''.
References
External links
Pandorina
- description with pictures
{{Authority control
Chlamydomonadales
Chlamydomonadales genera