''Trochiscia'' 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 ...
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
Oocystaceae
Oocystaceae is a family (biology), family of green algae, in the class Trebouxiophyceae. Molecular phylogenetic studies mostly (but not always) place the family in the order Chlorellales, as sister to Chlorellaceae. The Type (biology), type genus ...
. It is found in the
plankton
Plankton are the diverse collection of organisms that drift in Hydrosphere, water (or atmosphere, air) but are unable to actively propel themselves against ocean current, currents (or wind). The individual organisms constituting plankton are ca ...
of freshwater habitats. The name ''Trochiscia'' was used in 1834 by
Friedrich Traugott Kützing
Friedrich Traugott Kützing (8 December 1807 in Ritteburg – 9 September 1893) was a German pharmacist, botanist and phycologist.
Despite his limited background in regard to higher education, Kützing made significant scientific contribution ...
.
Description
''Trochiscia'' consists of solitary, spherical cells up to 50 μm in diameter. The
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, ...
s are thick, and are variously sculptured with spines, ribs, reticulations, and or projections. Cells are uninucleate (one
nucleus
Nucleus (: nuclei) is a Latin word for the seed inside a fruit. It most often refers to:
*Atomic nucleus, the very dense central region of an atom
*Cell nucleus, a central organelle of a eukaryotic cell, containing most of the cell's DNA
Nucleu ...
). The single
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 ...
is variable in morphology, and may be stellate and axial or parietal, and may have or lack a
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 ...
.
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 ...
occurs by the formation of
autospore
Autospores are a type of spores that are produced by algae to enable asexual reproduction and spread. They are non-motile and non-Flagellated cell, flagellated Aplanospore, aplanospores that are generated within a parent cell and have the same sha ...
s or
zoospore
A zoospore is a motile asexual spore that uses a flagellum for locomotion in aqueous or moist environments. Also called a swarm spore, these spores are created by some protists, bacteria, and fungi to propagate themselves. Certain zoospores are ...
s; sexual reproduction has not been observed.
[
Species of ''Trochiscia'' are distinguished based on details of cell morphology, particularly the sculpturing of the cell wall.][
]
Taxonomy
The taxonomy of ''Trochiscia'' is very unclear and in need of revision. The name ''Trochiscia'' was described twice by Kützing. His first description was in 1834, referring to a broad assemblage of green algae (including desmid
Desmidiales, commonly called the desmids (''Gr.'' ''desmos'', bond or chain), are an Order (biology), order in the Charophyta, a division of green algae in which the land plants (Embryophyta) emerged. Desmids consist of single-celled (sometimes fi ...
s) and diatom
A diatom (Neo-Latin ''diatoma'') is any member of a large group comprising several Genus, genera of algae, specifically microalgae, found in the oceans, waterways and soils of the world. Living diatoms make up a significant portion of Earth's B ...
s). The second description was in 1845, he had defined the genus for single, spherical to ellipsoidal cells which were polygonal or covered with spines or tubercles. This definition is approximately the current circumscription
Circumscription may refer to:
* Circumscribed circle
* Circumscription (logic)
*Circumscription (taxonomy)
* Circumscription theory, a theory about the origins of the political state in the history of human evolution proposed by the American anthr ...
of ''Trochiscia''.
Because the current naming of ''Trochiscia'' is predated by one in 1834, ''Trochiscia'' is a later homonym
In biology, a homonym is a name for a taxon that is identical in spelling to another such name, that belongs to a different taxon.
The rule in the International Code of Zoological Nomenclature is that the first such name to be published is the s ...
and needs to be replaced according to the rules of botanical nomenclature
Botanical nomenclature is the formal, scientific naming of plants. It is related to, but distinct from taxonomy (biology), taxonomy. Plant taxonomy is concerned with grouping and classifying plants; Botany, botanical nomenclature then provides na ...
. Currently, some of the species in ''Trochiscia'' were transferred to '' Glochiococcus''. However, most names within ''Trochiscia'' are poorly known and their true affinities are unknown.zygospore
A zygospore is a diploid reproductive stage in the life cycle of many fungi and protists. Zygospores are created by the nuclear fusion of haploid cells. In fungi, zygospores are formed in zygosporangia after the fusion of specialized budding stru ...
s or