Cochlosoma

''Cochlosoma'' is a genus of flagellated protozoa in the order Trichomonadida created by A. Kotlán (1923). Some of their typical features include a prominent adhesive disc, axostyle, costa, and six flagella – one of which is attached to an undulating membrane that runs laterally along the body.

''Cochlosoma'' species are parasites found in the intestines of birds and mammals. They are known to cause runting and enteritis in young turkey and ducks.

The genus currently contains five species, the most notable member being ''C. anatis'', a parasite of ducks and turkeys.

History of knowledge

''Cochlosoma'' was first described by Kotlán (1923) to include ''C. anatis'', a flagellate he found in the intestines of young European domestic ducks (''Anas platyrhynchos'') suffering from coccidiosis. ''Cochlosoma rostratum'' was identified in North American domestic ducks by Kimura in 1934, although this species is now recognized as a synonym of ''C.anatis¹''.

Kimura was the first to describe the morphology of ''Cochlosoma'' in great detail. A second species was described under the name ''Cyanthosoma striatum'' (Tyzzer, 1930) and was reassigned as ''Cochlosoma striatum'' by Kulda and Nohýnková (1978)². In 1938, Bernard V. Travis described two new species of ''Cochlosoma'', ''C. picae'' and C. turdi. The most recent addition to genus ''Cochlosoma'' is ''C. soricis'', which was found in shrews by Watkins et al. (1989)³.

''Cochlosoma'' was originally proposed to be part of diplomonads because their prominent adhesive disc is similar to that of '' Giardia¹''. In 1952, Grassé placed the genus into the order Retortamonadida⁵. However, morphological and ultrastructural observations (i.e. parabasal apparatus, pelta, costa, and axostyle) suggest the genus is more likely related to trichomonads and in 1996, Pecka et al. moved ''Cochlosoma'' to order Trichomonadida⁴. More recently, analysis of their rRNA gene sequence further supported their placement in Trichomonadida and led to their transfer from family Cochlosomatidae to family Trichomonadidae⁵.

Hosts

''Cochlosoma'' species are parasitic and commonly found in the cloaca, large intestine, and ceca¹. The following are some species and their known hosts:
* ''C. anatis'': reported in ducks and turkeys and has been experimentally transmitted to chickens^1,6
* ''C. picae'': magpie ( pica hudsonia)¹
* ''C. turdi'': American robin ( turdus migratorius)¹
* ''C. striatum'': ruffled grouse ( Bonasa umbelus)⁷
* ''C. sorecis'': Shrews³
* ''Cochlosoma sp''.: American magpies, eastern robins, bobwhite quail, songbirds, waterfowl, blue-faced parrot-finch, zebra finch, painted finch, nutmeg manikin, double-barred finch, red-headed parrot-finches, Bengalese finches, Lady Gould finches, and bats^3,7,8,9

Morphology

''Cochlosoma'' species have asymmetrical ovoidal shaped bodies (6-18 µm) that are broader anteriorly and narrower posteriorly. Their anterior end is truncated by a spiraled adhesive disc that is used to attach to the intestinal mucosa of the host. A lateral groove develops along the side of the body from the disc.

Six flagella of varying lengths arise from the anterior end of the cell. A recurrent flagellum is attached to the cell body by an undulating membrane and is free at the posterior end. The undulating membrane travels along the lateral groove and is supported by a conspicuous costa with type B periodicity. Four flagella are free and emerge anterolaterally from the lateral groove. The sixth flagellum emerges from a basal body the dorsal side of the body, independent of the basal body complex of the other flagella. Fibrillar appendages arise from the basal bodies. An axostyle also originates near the anterior basal bodies, passes through the body of the cell, and protrudes posteriorly.

They are uninucleate