''Mesofila'' () is a genus of freshwater

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

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 ...

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

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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 freshwater 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 Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typically a few micrometr ...

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 c ...

with rich organic mud from Palm Canyon,

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(

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References

External links

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