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Colpoda

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Colpoda



Colpoda is a genus of ciliate in the class Colpodea Order Colpodida Family Colpodidae.[1]

Description

Colpoda are distinctly hay infusions , especially when the sample does not come from an existing mature source of standing water.

Considering how common Colpoda are, how important they are in the world of microbes and how easily they are cultured (just pull up some grass, including a little dirt, then add with dechlorinated water to a jar), it is amazing that they don't come up more frequently in schools. Indeed, many high school students, after completing the biology chapter on microbes, will not know a colpoda when they see one and might think it is an oddly shaped or lopsided paramecium!

Habitat

Colpoda are often found in moist soil and because of their ability to readily enter protective cysts will quite frequently be found in desiccated samples of soil and vegetation[2] as well as in temporary natural pools such as tree holes.[3] They have also been found in the intestines of various animals, and can be cultured from their droppings,[4] although it is not clear that they are pathogenic. Indeed, it is generally believed that in most cases the animals ingested colpoda cysts that encrusted plants, or were contained in soil accidentally ingested and that these cysts simply passed through the digestive tract intact. This may be an important means of distribution that limits localization of colpoda populations which might otherwise lead to speciation.

Colpoda cucullus, on the other hand, has been found inhabiting the surface of plants and seems to dominate the microfauna there. It shouldn't be a surprise that several species of colpoda have been found in pitcher plants, despite the digestive enzymes.[5]

Colpoda also tend to be found in abundance where increased levels of bacteria offer an enriched food source. In Commercial chicken houses, for example, they seemed to be ubiquitous but the species found vary widely from one location to the next, suggesting that these populations represent local soil and aquatic populations which migrated into the new habitat.[6]

In addition to inhabiting a wide variety of microclimates, colpoda can be found almost everywhere around the world where there is standing water or moist soil, even where these conditions are only ephemeral. Colpoda brasiliensis for example was discovered in Brazilian floodplains in 2003.[7] Colpoda irregularis has been found in the high desert region of Southwest Idaho. Colpoda aspera has been found in the Antarctic. Colpoda are also found in the arctic where warmer temperatures and longer summers lead to greater density and species diversity.[8]

Not only is the genus widespread, there are also several species that have nearly global distribution, and, indeed, it has been suggested this may be true of all species, a fact that could be borne out by better investigation.[9] Though colpoda are not normally found in the marine environment, there are many ways they can travel from one continent to another. For example cysts can become lodged in the plumage of migratory birds, becoming dislodged hundreds or even thousands of miles away. Also, because cysts are so small and light, they can be swept by air currents into the upper atmosphere, and then come down on another continent.[10]

Reproduction

Colpoda normally divide in cysts, from which two to eight individuals emerge, four being the most common number. This produces genetically identical individuals. The rate at which such reproduction occurs and how it is affected by various environmental conditions has been the subject of a great deal of scientific research.[11]

On rare occasions, colpoda have been observed to divide into 4 individuals without producing a cyst wall. It has been suggested that cystless reproduction was the normal mode of reproduction for colpoda under optimum conditions and that the formation of cysts was a reaction to adverse environmental conditions. However, the knowledge gained by many years of culturing colpoda in hay infusions has shown that this mode of reproduction remains rare despite what would seem to be ideal environmental conditions.[12]

Colpoda can also reproduce by conjugation. This involves two colpoda joining at the oral groove and exchanging DNA, then later dividing, redistributing the DNA of the two original colpoda to produce numerous genetically distinct offspring. Note that the conjugation of colpoda seems to be a fairly rare phenomenon and there is some controversy regarding its very existence.[13] Though it should be noted that images purporting to show colpoda conjugation can be found on the internet.

Ecological Role

Most Colpoda species are either primarily or exclusively bactrivores feeding on a wide variety of bacteria, which include Moraxella. Several scientific studies have been made on the effect of different bacterial diets on the rate of colpoda reproduction. Much has been written on the ecological role that colpoda fulfill in the soil.[14]

In addition to their role as predators of bacteria, colpoda are themselves prey to large variety of species. This includes other protozoans as well as small animals such as mosquito larva,[15] other insect larva, and waterfleas.[16]

Uses by Man

In addition to their use in education and in a wide variety of scientific studies, colpoda have at times been suggested for more practical uses. For example the consistent effect of different bacteria in their diet on their rate of reproduction has been suggested as a means of identifying intestinal bacteria.[17] Colpoda steini has been suggested as a means to assess the toxicity of soil treated with sewage sludge[18] and as a means to detect chemical contamination in general, possibly in the wake of a terrorist attack.[19]

Species

Colpoda acuta
Found in central Europe, it was first described in a paper published in 1977.[20]

Colpoda aspera
A fairly small species, 12-42 micrometres, noted for being less reniform than other species. Found in Antarctic, Subantarctic [21][22][23]

Colpoda brasiliensis
A small species, 18-33 micrometres, noted for its mineral envelope which acts as a passive defense against predators. Named for the country in which it was discovered.[24]

Colpoda californica

Colpoda cavicola

Colpoda cucullus
A fairly widespread species noted for being the dominant protozoan on the surface of plants.[25][26]

Colpoda discoidea

Colpoda duodenaria
A small to medium sized species, first described by Charles Vincent Taylor and Waldo Furgason [27] and widely studied for the effects of various chemicals on its excystment process.[28]

Colpoda ecaudata

Colpoda elliotti
A small species, 15-28 micrometres, noted as having been cultured from deer droppings.[29]

Colpoda eurystoma

Colpoda fastigata

Colpoda formisanoi

Colpoda fragilis

Colpoda henneguyi
Widespread medium to large species, 30-80 micrometres, noted for its habit of staying perfectly still for long periods of time, making it easy to photograph live.[30]

Colpoda inflata
Possibly one of the best known and most common species, noted for its fitful resting stage in which it jerks around in a tight circle, frustrating microscopists trying to photograph it live.[31][32]

Colpoda irregularis
This species is noted for a prominent post oral sac and was cultured from moss and soil crust from rocks near desert sagebrush of southwest Idaho.[33]

Colpoda lucida

Colpoda magna
A large species, 120-400 micrometres long. Appears dark at lower powers because of dark structures near the contractile vacuole. Often completely packed with food vacuoles.[34]

Colpoda maupasi
Once thought to be a variety of Colpoda steini, later recognized as a separate species. Classically it was believed to produce only reproductive cysts containing 8 offspring. One strain, however, the Bensonhurst strain, was found to also produce reproductive cysts containing 4 offspring.[35]

Colpoda ovinucleata

Colpoda patella

Colpoda penardi

Colpoda praestans

Colpoda quinquecirrata

Colpoda reniformis

Colpoda rotunda

Colpoda simulans
A medium sized colpoda with the classic "bite taken out of it" colpoda shape.[36]

Colpoda spiralis
A very unusual species with a large overhang that gives it an almost snail like appearance. It was first found in Arizona [3] and has since been reported in New Mexico and Nevada, with a possible sighting in Northern California.[37]

Colpoda steini
A widely distributed small to mid sized species, 14-60 micrometres, usually free living but capable of being parasitic to land slugs.[38]

Colpoda tripartita

Colpoda variabili

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References

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