Colpoda are distinctly reniform (kidney-shaped) and are strongly convex on one side, and concave on the other. The concave side often looks like a bite was taken out of it. Although they are not as well known as theparamecium, they are often the firstprotozoa to appear inhay infusions, especially when the sample does not come from an existing mature source ofstanding water.
More detailed image of various sizedColpoda at 400X
Colpoda are often found in moistsoil and because of their ability to readily enter protectivecysts will quite frequently be found in desiccated samples of soil and vegetation[3] as well as in temporarynatural pools such astree holes.[4]They have also been found in theintestines of various animals, and can be cultured from their droppings.[5]
Colpoda cucullus has been found inhabiting the surface of plants and seems to dominate themicrofauna there. Several species ofColpoda have been found in the pitcher plantSarracenia purpurea, despite the presence ofprotease digestive enzymes in the liquid.[6]
Colpoda also tends to be found in abundance where increased levels ofbacteria offer an enriched food source. In commercialchicken 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.[7]
In addition to inhabiting a wide variety ofmicroclimates,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 inBrazilianfloodplains in 2003.[8]Colpoda irregularis has been found in the highdesert region of SouthwestIdaho.Colpoda aspera has been found in theAntarctic.Colpoda are also found in thearctic where warmer temperatures and longer summers lead to greater density andspecies diversity.[9]
Not only is the genus widespread, but 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.[10] ThoughColpoda 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 migratorybirds, becoming dislodged hundreds or even thousands of miles away. Also, because cysts are so small and light, they can be swept byair currents into theupper atmosphere, and then come down on another continent.[11]
Colpoda normally divides into 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.[12]
On rare occasions,Colpoda have been observed to divide into 4 individuals without producing a cyst wall. It has been suggested that cyst less reproduction was the normal mode of reproduction forColpoda under optimum conditions and that the formation of cysts was a reaction to adverse environmental conditions. However, the knowledge gained by many years of culturingColpoda in hay infusions has shown that this mode of reproduction remains rare despite what would seem to be ideal environmental conditions.[13]
As in other ciliates, division inColpoda may be preceded by a sexual phenomenon known asconjugation. This involves twoColpoda joining at theoral groove and exchangingDNA. Following conjugation, theColpoda divides, redistributing the DNA of the two original cells to produce numerous genetically distinct offspring.[14][15][16]
MostColpoda species are either primarily or exclusivelybacterivores feeding on a wide variety of bacteria, which includeMoraxella. Several scientific studies have been made on the effect of different bacterial diets on the rate ofColpoda reproduction. Much has been written on the ecological role thatColpoda fulfill in the soil.[17]
In addition to their role as predators of bacteria,Colpoda are themselves prey to a large variety of species. This includes otherprotozoans as well as small animals such asmosquito larva,[18] other insectlarva, andwaterfleas.[19]
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.Colpoda steini has been suggested as a means to assess the toxicity of soil treated withsewage sludge[20] and as a means to detect chemical contamination in general, possibly in the wake of aterrorist attack.[21]
Colpoda acuta - Found in central Europe, it was first described in a paper published in 1977.[22]
Colpoda aspera - A fairly small species, 12-42 micrometres, noted for being less reniform than other species. Found in Antarctic, Subantarctic[23][24][25]
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.[26]
Colpoda duodenaria - A small to medium-sized species, first described by Charles Vincent Taylor and Waldo Furgason[29] and widely studied for the effects of various chemicals on its excystment process.[30]
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.[32]
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.[33][34]
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 foodvacuoles.[36]
Colpoda maupasi - Once thought to be a variety ofColpoda steini, later recognized as a separate species. Classically it was believed to produce only reproductive cysts containing 8 offspring. One strain, however, theBensonhurst strain, was found to also produce reproductive cysts containing 4 offspring.[37]
Colpoda simulans - A medium-sizedColpoda with the classic "bite taken out of it"Colpoda shape.[38]
Colpoda spiralis - A very unusual species with a large overhang that gives it an almost snail-like appearance. It was first found in Arizona[4] and has since been reported in New Mexico and Nevada, with a possible sighting in Northern California.[39]
Colpoda steini - A widely distributed small to mid-sized species, 14-60 micrometres, usually free living but capable of being parasitic toland slugs.[40]
^Foissner, W. (January 2003). "Pseudomaryna australiensis nov. gen., nov. spec. andColpoda brasiliensis nov. spec., two new colpodids (Ciliophora, Colpodea) with a mineral envelope".European Journal of Protistology.39 (2):199–212.doi:10.1078/0932-4739-00909.S2CID83583325.
^Finlay, Bland J.; Esteban, Genoveva F.; Clarke, Ken J.; Olmo, José L. (December 2001). "Biodiversity of Terrestrial Protozoa Appears Homogeneous across Local and Global Spatial Scales".Protist.152 (4):355–366.doi:10.1078/1434-4610-00073.PMID11822663.
^Use ofColpoda steinii to bioassay the toxicity and bioavailability of heavy metals in a long term sewage sludge-treated soil., Campbell, C.D., Warren, A., Cameron, C.M. and Hope, S.J., (1995) British Section of the Society of Protistologists, Annual Meeting, Liverpool, 27–29 March 1995.
^Pozdnyakova, L.I.; Lozitsky, V.P.; Fedchuk, A.S.; Grigorasheva, I.N.; Boshchenko, Y.A.; Gridina, T.L.; Pozdnyakov, S.V. (2006), "Biological Method for the Water, Food, Fodders, and Environment Toxic Chemical Materials Contamination Indication",Medical Treatment of Intoxications and Decontamination of Chemical Agent in the Area of Terrorist Attack, NATO Security Through Science Series, vol. 1, Kluwer Academic Publishers, pp. 225–230,doi:10.1007/1-4020-4170-5_26,ISBN978-1402041686
^Petz, W.; Foissner, W. (1997) Morphology and infraciliature of some soil ciliates (Protozoa, Ciliophora) from continental Antarctica, with notes on the morphogenesis of Sterkiella histriomuscorumPolar Record 33, Issue 187 307-326pp.
^Foissner, W. (2003). "Pseudomaryna australiensis nov. gen., nov. spec. andColpoda brasiliensis nov. spec., two new colpodids (Ciliophora, Colpodea) with a mineral envelope".European Journal of Protistology.39 (2):199–212.doi:10.1078/0932-4739-00909.S2CID83583325.
^Bhaskaran K, Nadaraja AV, Balakrishnan MV, Haridas A (March 2008). "Dynamics of sustainable grazing fauna and effect on the performance of gas biofilter".J. Biosci. Bioeng.105 (3):192–7.doi:10.1263/jbb.105.192.PMID18397767.
^Reynolds, Bruce D. (1936). "Colpoda steini, a Facultative Parasite of the Land Slug, Agriolimax agrestis".The Journal of Parasitology.22 (1):48–53.doi:10.2307/3271896.JSTOR3271896.
