The synurids (order Synurales) are a small group of

heterokont Heterokonts are a group of protists (formally referred to as Heterokonta, Heterokontae or Heterokontophyta). The group is a major line of eukaryotes. Most are algae, ranging from the giant multicellular kelp to the unicellular diatoms, which ...

algae, found mostly 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. Although the term specifically excludes seawater and brackish water, it does include ...

environments, characterized by cells covered in

silica Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is one ...

scales.

Characteristics

They are covered in silicate scales and spines. In ''Synura'', these are formed on the surface of the

chloroplast A chloroplast () is a type of membrane-bound organelle known as a plastid that conducts photosynthesis mostly in plant and algal cells. The photosynthetic pigment chlorophyll captures the energy from sunlight, converts it, and stores it in ...

s, two of which are usually present, but sometimes only one divided into two lobes is seen. The cells have two heterokont

flagella A flagellum (; ) is a hairlike appendage that protrudes from certain plant and animal sperm cells, and from a wide range of microorganisms to provide motility. Many protists with flagella are termed as flagellates. A microorganism may have f ...

, inserted parallel to one another at the anterior, whose ultrastructure is a distinguishing characteristic of the group. Both asexual and

isogamous Isogamy is a form of sexual reproduction that involves gametes of the same morphology (indistinguishable in shape and size), found in most unicellular eukaryotes. Because both gametes look alike, they generally cannot be classified as male or fe ...

sexual reproduction occur.

Genera

Two major genera are included here, divided into species mainly based on the structure of the scales. * ''

Mallomonas ''Mallomonas'' is a genus comprising unicellular algal eukaryotes and characterized by their intricate cell coverings made of silica scales and bristles. The group was first named and classified by Dr. Maximilian Perty in 1852. These organisms l ...

'' species are free-living individual cells, usually 50-100 μm in length. They have ornate scales and generally long spines. * ''

Synura ''Synura'' is a genus of colonial chrysomonad algae covered in silica scales. It is the most conspicuous genus of the order Synurales The synurids (order Synurales) are a small group of heterokont algae, found mostly in freshwater environments ...

'' species occur as spherical colonies, with the cells oriented so that the flagella point outwards, each usually around 30 μm in length. The colonies are globular, rather than hollow, and spines are short if at all present. Both are common

plankton Plankton are the diverse collection of organisms found in Hydrosphere, water (or atmosphere, air) that are unable to propel themselves against a Ocean current, current (or wind). The individual organisms constituting plankton are called plankt ...

in lakes and ponds. In high concentrations, they dye the water yellow, and produce a distinctive odour. To reproduce the parent cell splits into two daughter cells which get half of the parent cells scales. The new cells can regrow the scales and grow back into their original form.

History

The genus ''Synura'' was proposed in 1834 by the German microscopist

Christian Gottfried Ehrenberg Christian Gottfried Ehrenberg (19 April 1795 – 27 June 1876) was a German naturalist, zoologist, comparative anatomist, geologist, and microscopist. Ehrenberg was an evangelist and was considered to be of the most famous and productive scie ...

(1795–1876). The synurids were originally included among the

golden alga The Chrysophyceae, usually called chrysophytes, chrysomonads, golden-brown algae or golden algae are a large group of algae, found mostly in freshwater. Golden algae is also commonly used to refer to a single species, '' Prymnesium parvum'', whi ...

e in the order Ochromonadales as the family Mallomonadaceae or as the family Synuraceae . They were formally defined as a separate group by Andersen in 1987, who placed them in their own class Synurophyceae, based on an earlier approach of more narrowly defining major lineages of chrysophyte algae by British phycologist David Hibberd. The

Chrysophyceae The Chrysophyceae, usually called chrysophytes, chrysomonads, golden-brown algae or golden algae are a large group of algae, found mostly in freshwater. Golden algae is also commonly used to refer to a single species, ''Prymnesium parvum'', whic ...

and Synurophyceae are currently recognized as closely related taxa within the

Stramenopile Stramenopile is a clade of organisms distinguished by the presence of stiff tripartite external hairs. In most species, the hairs are attached to flagella, in some they are attached to other areas of the cellular surface, and in some they have be ...

s. Present classifications include the synurids as an order (Synurales) within

References

External links

Ochrophyta Heterokont orders {{Heterokont-stub