| Platydorina | |
|---|---|
 | |
| Stained coenobia | |
Scientific classification  | |
| (unranked): | Viridiplantae |
| Division: | Chlorophyta |
| Class: | Chlorophyceae |
| Order: | Chlamydomonadales |
| Family: | Volvocaceae |
| Genus: | Platydorina Kofoid |
| Species: | P. caudata |
| Binomial name | |
| Platydorina caudata Kofoid | |
Platydorina is a genus of microscopic green algae in the family Volvocaceae. [1] It contains only one species, Platydorina caudata. [2] It was described by Charles Atwood Kofoid in 1899. [3]
Platydorina caudata consists of a flattened, horseshoe-shaped coenobium containing 16 or 32 cells embedded in a transparent, gelatinous matrix. Cells have two flagella that protrude out of the matrix. Each cell is uniformly sized and colored green from a single cup-shaped chloroplast containing a pyrenoid, with a circular red eyespot and two contractile vacuoles. At one end the matrix is rounded, while at the other end it is drawn out into a few rounded "tails". [3]
Platydorina caudata is planktonic, and moves in a spiral motion, twisting to the left. [3]
Platydorina caudata reproduces both sexually and asexually. In asexual reproduction, cells in the coenobium divide continuously until they reach a certain cell count, 16 or 32 cells. At this point, the flagella are pointing inward, but the colony flips inside out (a process known as colony inversion) such that the flagella now point outward. The colony, which is spherical, flattens out into the characteristic horseshoe-shape. After the gelatinous matrix forms, the new colony separates from the parent. [4]
In sexual reproduction, colonies may be either male or female and produce sperm or egg cells, respectively. It is anisogamous, meaning the gametes are differently sized. Both sperm and egg cells are released, where they swim about until fertilized. Egg cells escape in an unusual way; a pore forms, and then the egg cell squeezes through the pore until it is released. [4]
The Chlorophyceae are one of the classes of green algae, distinguished mainly on the basis of ultrastructural morphology. They are usually green due to the dominance of pigments chlorophyll a and chlorophyll b. The chloroplast may be discoid, plate-like, reticulate, cup-shaped, spiral- or ribbon-shaped in different species. Most of the members have one or more storage bodies called pyrenoids located in the chloroplast. Pyrenoids contain protein besides starch. Some green algae may store food in the form of oil droplets. They usually have a cell wall made up of an inner layer of cellulose and outer layer of pectose.
Volvox is a polyphyletic genus of chlorophyte green algae in the family Volvocaceae. Volvox species form spherical colonies of up to 50,000 cells, and for this reason they are sometimes called globe algae. They live in a variety of freshwater habitats, and were first reported by Antonie van Leeuwenhoek in 1700. Volvox diverged from unicellular ancestors approximately 200 million years ago.
Chlamydomonadales, also known as Volvocales, are an order of flagellated or pseudociliated green algae, specifically of the Chlorophyceae. Chlamydomonadales can form planar or spherical colonies. These vary from Gonium up to Volvox. Each cell has two flagella, and is similar in appearance to Chlamydomonas, with the flagella throughout the colony moving in coordination.
Desmidiales, commonly called the desmids, are an order in the Charophyta, a division of green algae in which the land plants (Embryophyta) emerged. Desmids consist of single-celled microscopic green algae. Because desmids are highly symmetrical, attractive, and come in a diversity of forms, they are popular subjects for microscopists, both amateur and professional.
Holoplankton are organisms that are planktic for their entire life cycle. Holoplankton can be contrasted with meroplankton, which are planktic organisms that spend part of their life cycle in the benthic zone. Examples of holoplankton include some diatoms, radiolarians, some dinoflagellates, foraminifera, amphipods, krill, copepods, and salps, as well as some gastropod mollusk species. Holoplankton dwell in the pelagic zone as opposed to the benthic zone. Holoplankton include both phytoplankton and zooplankton and vary in size. The most common plankton are protists.
Plant reproduction is the production of new offspring in plants, which can be accomplished by sexual or asexual reproduction. Sexual reproduction produces offspring by the fusion of gametes, resulting in offspring genetically different from either parent. Asexual reproduction produces new individuals without the fusion of gametes, resulting in clonal plants that are genetically identical to the parent plant and each other, unless mutations occur.
In botany, a zoid or zoïd is a reproductive cell that possesses one or more flagella, and is capable of independent movement. Zoid can refer to either an asexually reproductive spore or a sexually reproductive gamete. In sexually reproductive gametes, zoids can be either male or female depending on the species. For example, some brown alga (Phaeophyceae) reproduce by producing multi-flagellated male and female gametes that recombine to form the diploid sporangia. Zoids are primarily found in some protists, diatoms, green alga, brown alga, non-vascular plants, and a few vascular plants. The most common classification group that produces zoids is the heterokonts or stramenopiles. These include green alga, brown alga, oomycetes, and some protists. The term is generally not used to describe motile, flagellated sperm found in animals. Zoid is also commonly confused for zooid which is a single organism that is part of a colonial animal.
Dictyosphaeriaceae is a family of green algae. As of February 2022, AlgaeBase places two genera in the family:
Astrephomene is a genus of green algae in the family Goniaceae, order Chlamydomonadales. The genus was first described in 1937 by Pocock and named by Pockock in 1953.
Coelastropsis is a genus of green algae in the family Scenedesmaceae, containing the single species Coelastropsis costata. It is found in freshwater lakes and bogs, usually associated with mosses and filamentous algae. It has been recorded in Europe, Cuba and possibly New Zealand.
Neodesmus is a genus of green algae in the family Scenedesmaceae.
Sorastrum is a genus of green algae in the family Hydrodictyaceae. It is a component of the phytoplankton of freshwater ponds, lakes, and ditches. Sorastrum is common in tropical to temperate regions of the world, but due to its small size it is often overlooked.
Stephanosphaera is a genus of green algae in the family Haematococcaceae, containing the single species Stephanosphaera pluvialis. It forms colonies of flagellated cells. Although it was once placed in the family Volvocaceae, it is not closely related to them; its sister is the unicellular genus Balticola.
Volvulina is a genus of colonial green algae in the family Volvocaceae. The colony (coenobium) is broadly ellipsoidal or spherical and consists of a fixed number of cells, usually 16 in mature individuals. The cells are located at periphery of the coenobium and separated from each other by being embedded in a swollen sack. The cell body is lens-shaped or half spherical when mature with two flagella. The chloroplast is dish- or bowl-shaped. Pyrenoids may be present or absent, the stigma large. The nucleus is centrally located and there may be 4 to 8 contractile vacuoles. Sexual reproduction is by isogamy.
Spinoclosterium is a genus of green algae, specifically of the Closteriaceae. It is rare, but widely distributed in freshwater regions throughout the world.
Gilbertsmithia is a genus of green algae in the family Scenedesmaceae, containing the single species Gilbertsmithia grandis. It was named after the American botanist Gilbert Morgan Smith. This remarkable alga has only been recorded once from a muddy rainwater pool in Madras, India.
Characiella is a genus of green algae in the family Characiaceae, containing the single species Characiella rukwae.
Dinophysis is a genus of dinoflagellates common in tropical, temperate, coastal and oceanic waters. It was first described in 1839 by Christian Gottfried Ehrenberg.
Alexandrium monilatum is a species of armored, photosynthetic, marine dinoflagellates. It produces toxins that, when present in high concentrations as "red tides", can kill fish and reduce growth rates of shellfish.
Lemmermannia /ˌlɛməɹˈmæniə/ is a genus of fresh water trebouxiophyceans. as of March 2022, the genus contains five described species. They form coenobia of 4 to 16 cells. Its type species is L. tetrapedia (Kirchner) Lemmermann, originally described in 1880 but put into the genus Lemmermannia in 1904.