''Paradoxia'' 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 microscopic

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 Coccomyxaceae. It 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 as

phytoplankton Phytoplankton () are the autotrophic (self-feeding) components of the plankton community and a key part of ocean and freshwater Aquatic ecosystem, ecosystems. The name comes from the Greek language, Greek words (), meaning 'plant', and (), mea ...

worldwide, but species are rare.

Description

''Paradoxia'' consists of individual cells or pairs of cells. Individual cells are club-shaped or fusiform in outline, 18–45 μm long and 3–8 μm wide. When paired, the two cells are joined at the base by spines or leaf-like appendages that twist together. These leaf-like appendages have many fine curved ridges on one face. 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, ...

is smooth and covered with thin spines up to 24 μm long. Cells are uninucleate (i.e. with 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 ...

) and one

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 ...

containing a single

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 ...

. Reproduction occurs asexually via 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 which form a coenobium while still in the mother cell wall.

Resting spore A resting spore is a resistant cell, adapted to survive adverse environmental conditions. Resting spore is a term commonly applied to both diatoms and fungi. In fungi and oomycetes A resting spore can be a spore created by fungi which is thickly ...

s have also been reported.

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 ...

has not been observed in this genus. ''Paradoxia'' species are distinguished by the morphology of the cells, and whether or not they are paired. The genus may be closely related to others with leaf-like appendages at the cell ends, in particular ''

Ankyra ''Ankyra'' is a genus of green algae in the family Characiaceae. This genus of algae is closely related to '' Atractomorpha'' and ''Sphaeroplea''. They are found in stagnant waters. ''Ankyra'' consists of single cells that are planktonic or epi ...

''.

Taxonomy

Sources disagree on where to place ''Paradoxia'' taxonomically. In their 1983

monograph A monograph is generally a long-form work on one (usually scholarly) subject, or one aspect of a subject, typically created by a single author or artist (or, sometimes, by two or more authors). Traditionally it is in written form and published a ...

Jiří Komárek Jiří (; ''YI-RZHEE'') is a Czech masculine given name, equivalent to English George. Notable people with the name include: B *Georg Benda (Jiří Antonín Benda), Czech composer, violinist and Kapellmeister *Jiří Baborovský, Czech physica ...

and

Bohuslav Fott Bohuslav (, ; ) is a city on the Ros River in Obukhiv Raion, Kyiv Oblast, Ukraine. It hosts the administration of Bohuslav urban hromada, one of the hromadas of Ukraine. Population: 17,135 (2001). It is known as Boslov by some of its Yiddish ...

placed ''Paradoxia'' in the family

Characiaceae Characiaceae is a family of green algae in the order Sphaeropleales. It contains epiphytic or planktonic algae that are unicellular or colonial. The cells are heteropolar, with basal and apical ends having different shapes. The daughter cells are ...

. A strain labeled as ''Paradoxia multiseta'' in the UTEX-Austin

culture collection A microbiological culture, or microbial culture, is a method of multiplying microbial organisms by letting them reproduce in predetermined culture medium under controlled laboratory conditions. Microbial cultures are foundational and basic diagn ...

was found to have a close

phylogenetic In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical dat ...

relationship to ''

Coccomyxa ''Coccomyxa'' is a genus of green algae in the family Coccomyxaceae. This genus is defined by their small, elliptical to spherical shape, and the presence of a simple parietal chloroplast. These features, along with their occurrence in various l ...

''; however, the morphology of the strain (having spherical cells) does not appear to match that of ''Paradoxia'', making the identity suspect.

References

External links

AlgaTerra database

Index Nominum Genericorum
Trebouxiophyceae genera Trebouxiophyceae Enigmatic algae taxa Freshwater algae {{Green alga-stub