''Mesofila'' () is a genus of

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 ...

heterotrophic A heterotroph (; ) is an organism that cannot produce its own food, instead taking nutrition from other sources of organic carbon, mainly plant or animal matter. In the food chain, heterotrophs are primary, secondary and tertiary consumers, but ...

protist A protist () is any eukaryotic organism (that is, an organism whose cells contain a cell nucleus) that is not an animal, plant, or fungus. While it is likely that protists share a common ancestor (the last eukaryotic common ancestor), the exc ...

s of the phylum

Cercozoa Cercozoa is a phylum of diverse single-celled eukaryotes. They lack shared morphological characteristics at the microscopic level, and are instead defined by molecular phylogenies of rRNA and actin or polyubiquitin. They were the first major eu ...

. It is the only genus in the family Mesofilidae. It is a monotypic genus, with the sole species ''M. limnetica'' ().

Morphology

''Mesofila limnetica'' are small biciliate

amoebae An amoeba (; less commonly spelled ameba or amœba; plural ''am(o)ebas'' or ''am(o)ebae'' ), often called an amoeboid, is a type of cell or unicellular organism with the ability to alter its shape, primarily by extending and retracting pseudopo ...

with several, extremely long, branching

filopodia Filopodia (singular filopodium) are slender cytoplasmic projections that extend beyond the leading edge of lamellipodia in migrating cells. Within the lamellipodium, actin ribs are known as ''microspikes'', and when they extend beyond the lame ...

that, unlike

Heliomorphidae ''Heliomorpha'' is a genus of Cercozoa, placed in its own family, Heliomorphidae. It used to be known as "''Dimorpha''", but that name was a junior synonym several times over. References Filosa Cercozoa genera Taxa named by Thomas Cav ...

, do not radiate in three dimensions but rather remain in contact against the substrate during feeding. The two long

cilia The cilium, plural cilia (), is a membrane-bound organelle found on most types of eukaryotic cell, and certain microorganisms known as ciliates. Cilia are absent in bacteria and archaea. The cilium has the shape of a slender threadlike projecti ...

and the long filopodia can be present simultaneously or each on their own, depending on the life cycle phase. ''Mesofila'' have two phases: amoeboid and flagellate. *

Amoeboid An amoeba (; less commonly spelled ameba or amœba; plural ''am(o)ebas'' or ''am(o)ebae'' ), often called an amoeboid, is a type of cell or unicellular organism with the ability to alter its shape, primarily by extending and retracting pseudopo ...

phase. The immotile amoeboid cells are 9 to 14 μm in diameter and have a circular or slightly polygonial shape with a pitted surface. The central

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 Nucle ...

takes up around a quarter of the cell body's diameter and has a conspicuous

nucleolus The nucleolus (, plural: nucleoli ) is the largest structure in the nucleus of eukaryotic cells. It is best known as the site of ribosome biogenesis, which is the synthesis of ribosomes. The nucleolus also participates in the formation of sig ...

in its center. The filopodia appear from all around the cell, but slightly thicker filopodia usually emerge from the cell poles. The filopodia can grow to be around 10 times the cell's diameter, and they carry evenly and closely-spaced prominent granules. *

Flagellate A flagellate is a cell or organism with one or more whip-like appendages called flagella. The word ''flagellate'' also describes a particular construction (or level of organization) characteristic of many prokaryotes and eukaryotes and their ...

phase. The motile flagellate cells are ovoid, around 8 μm in length, with two

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 ...

: an anterior flagellum that beats vigorously, often curving round on itself, measuring 0.5 to 1 times the cell's length; and a posterior flagellum that trails, measuring 2 to 2.5 times the cell's length. They

glide Glide may refer to: * Gliding flight, to fly without thrust Computing *Glide API, a 3D graphics interface *Glide OS, a web desktop *Glide (software), an instant video messenger *Glide, a molecular docking software by Schrödinger (company), Schr� ...

erratically and swiftly, with the thicker, posterior end of the cell raised off the substrate. They also swim rapidly in a helical motion. They can also form spherical cysts with a smooth, refractile surface, measuring around 10 μm in diameter.

Ecology

''Mesofila limnetica'' are

bacterivorous A bacterivore is an organism which obtains energy and nutrients primarily or entirely from the consumption of bacteria. The term is most commonly used to describe free-living, heterotrophic, microscopic organisms such as nematodes as well as many s ...

amoebae. When the bacterial density is high they can grow very densely, and

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...

accumulate and obscure the cell body. They were isolated from a

hot spring A hot spring, hydrothermal spring, or geothermal spring is a spring produced by the emergence of geothermally heated groundwater onto the surface of the Earth. The groundwater is heated either by shallow bodies of magma (molten rock) or by circ ...

with rich organic mud from Palm Canyon,

California California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...

(

USA The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...

References

External links

{{taxonbar, from1=Q1552196, from2=Q19842472, from3=Q19842473 Cercozoa genera