Gromia
Encyclopedia
Gromia is a widespread genus of marine and freshwater amoeboid
s, closely resembling some foraminifera
ns. It produces an organic test
, which is ovoid or lobed and may exceed one millimetre in size; this resembles a small grape, in that its centre is fluid-filled but lacks organic matter, which is concentrated in its translucent test and underlying sediment, making the organism almost neutrally buoyant. Filose pseudopods emerge from a single opening in the test. They branch and may merge together again, but unlike the pseudopods of true foraminiferans they are not granular and rarely form a network. The life-cycle involves both asexual and sexual reproduction, and at certain stages motile cells with two flagella
are produced.
On molecular trees Gromia is separated from other filose amoebae, which are mostly core Cercozoa
, and appears between the Cercozoa and Foraminifera. It may be placed as the closest living relative of the foraminiferans, but rapid genetic divergence between several groups makes this difficult to confirm.
Gromia can produce traces on the sea floor as it rolls around, which bear a resemblance to early trace fossils. These tracks are sinuous grooves, and are bordered by two squat, relatively wide ridges.
Gromia sphaerica
is a large amoeboid
discovered in the Arabian Sea.
Amoeboid
Amoeboids are single-celled life-forms characterized by an irregular shape."Amoeboid" and "amœba" are often used interchangeably even by biologists, and especially refer to a creature moving by using pseudopodia. Most references to "amoebas" or "amoebae" are to amoeboids in general rather than to...
s, closely resembling some foraminifera
Foraminifera
The Foraminifera , or forams for short, are a large group of amoeboid protists which are among the commonest plankton species. They have reticulating pseudopods, fine strands of cytoplasm that branch and merge to form a dynamic net...
ns. It produces an organic test
Test (biology)
A test is a term used to refer to the shell of sea urchins, and also the shell of certain microorganisms, such as testate foraminifera and testate amoebae....
, which is ovoid or lobed and may exceed one millimetre in size; this resembles a small grape, in that its centre is fluid-filled but lacks organic matter, which is concentrated in its translucent test and underlying sediment, making the organism almost neutrally buoyant. Filose pseudopods emerge from a single opening in the test. They branch and may merge together again, but unlike the pseudopods of true foraminiferans they are not granular and rarely form a network. The life-cycle involves both asexual and sexual reproduction, and at certain stages motile cells with two flagella
Flagellum
A flagellum is a tail-like projection that protrudes from the cell body of certain prokaryotic and eukaryotic cells, and plays the dual role of locomotion and sense organ, being sensitive to chemicals and temperatures outside the cell. There are some notable differences between prokaryotic and...
are produced.
On molecular trees Gromia is separated from other filose amoebae, which are mostly core Cercozoa
Cercozoa
The Cercozoa are a group of protists. They are sometimes described as a kingdom.-Characteristics:The group includes most amoeboids and flagellates that feed by means of filose pseudopods. These may be restricted to part of the cell surface, but there is never a true cytostome or mouth as found in...
, and appears between the Cercozoa and Foraminifera. It may be placed as the closest living relative of the foraminiferans, but rapid genetic divergence between several groups makes this difficult to confirm.
Gromia can produce traces on the sea floor as it rolls around, which bear a resemblance to early trace fossils. These tracks are sinuous grooves, and are bordered by two squat, relatively wide ridges.
Gromia sphaerica
Gromia sphaerica
Gromia sphaerica is a large spherical testate amoeba, a single-celled organism classed among the protists and is the largest in the genus Gromia. It was discovered in 2000, along the Oman margin of the Arabian sea, at depths from 1163 to 1194 meters . Specimens range in size from 4.7 to 38...
is a large amoeboid
Amoeboid
Amoeboids are single-celled life-forms characterized by an irregular shape."Amoeboid" and "amœba" are often used interchangeably even by biologists, and especially refer to a creature moving by using pseudopodia. Most references to "amoebas" or "amoebae" are to amoeboids in general rather than to...
discovered in the Arabian Sea.