Trichodina Ehrenberg, 1830 (ref. ID; 2014)
Class Oligohymenophora: Subclass Peritricha: Order Peritrichida: Suborder Mobilina (ref. ID; 2014)
Phylum Ciliophora Dorflein, 1901: Class Oligohymenophora de Puytorac et al., 1974: Subclass Peritrichia Stein, 1859: Order Peritrichida Stein, 1859: Suborder Mobilina Kahl, 1933: Family Trichodinidae Claus, 1874 (ref. ID; 7416)

[ref. ID; 2014]
Body shape varies from cylindrical to discoidal. The peristomial ciliary wreaths always make a complete circle and sometimes the ends overlap (360-400 degrees). The aboral disc is typically suctorial with hook-like elements possessing, both centrifugal processes and centripedal rays. The macronucleus is usually horseshoe-shaped, lying centrally in the body in a horizontal plane. Freshwater species of this genus may be found on Hydra, bryozoa, trematodes, planarians, molluscs, amphibians and fishes. The genus is most easily confused with Urceolaria in which the denticles are without processes and rays.
Quote; Colin R. Curds, Michael A. Gates and David McL. Roberts "British and other freshwater ciliated protozoa Part II Ciliophora: Oligohymenophora and Polyhymenophora" Cambridge University Press, 1983 (ref. ID; 2014)

Trichodina ctenophorii Estes et al., 1997 (ref. ID; 7416 original paper)
Description; In profile, Trichodina ctenophorii varied in shape from a flat disc to a dome in each population and at all collection sites. We suspect that this variability depends on the physiological state of the ciliate, for instance, whether it is attached tightly to the substrate, is about to release from the comb plate, or is loosely attached. The adoral ciliary wreath wrapped ~ 390 (range: 380-415 degrees) about the oral surface. Silver staining revealed a clear adhesive disk center with irregular dark granules. The adhesive disc in all cells was flat and circular in shape. T. ctenophorii varied somewhat in size with regard to its locality. Denticular morphology and associated structures were the same at all locations. (ref. ID; 7416)
[Denticular anatomy]: The structure comprising the denticular ring displayed a unique morphology. The blades were falcate, forming an overall triangular shape with a blunt or rounded tip. There were no notches or indentations on the posterior of the blade. The thorns were long, this, and straight with a blunt tip. The knobs of the denticular ring were also blunt-tipped. (ref. ID; 7416)
[Young cells]: Two smaller specimens with extremely short thorns were not included in these overall measurements. These trichodinids however, had values of other morphological measurements such as the number of denticles, pin number, blade, thorn, and knob sizes similar to the above specimens. By these criteria we identified them as young cells. Uzmann and Stickney have described such cells as the recent products of cell division that had yet to lengthen and thicken their thorns (Uzmann and Stickney, 1954). Their measurements were as follows (mean dimension (range)): body size 28.9 um (28.8-29); adhesive disk 24.5 um (24-25); denticle ring 17.4 um (17.3-17.5); blades 2.8 um (2.6-3); thorns 1.2 um; knob 0.85 um (0.8-0.9); border membrane 1.9 um (1.3-2.4); denticle number 26, and there were five pins per denticle. (ref. ID; 7416)
[Macronucleus]: VE-DIC and silver-stained preparations revealed a 5 um wide, 27.8 um diameter horseshoe-shaped macronucleus. The plane of the macronucleus was parallel to the plane of the denticular ring with its open end directly below and rotated CCW ~ 5 degree from the couterclockwise-most edge of the adoral ciliary ring. (ref. ID; 7416)
Notes; Trichodina ctenophorii is similar in denticular morphology to T. mutabilis, T. nigra, T. hypsilepis and T. microdenticula, T. mutabilis, from the gills of the carp Cyprinus carpio L. (Kazubski et al. 1968; Lom 1970) had a similar number of denticles (29 (26-30)) and similar denticle morphology to that of T. ctenophorii; however, it was much larger with an overall diameter of 77.6 um (60.4-106), border membrane size of 6 um and 9-10 radial pins per denticle. Blades were spade-shaped and the center of the adhesive disk uniformaly dark. The macronucleus was 55.7 um (45-63.5) in diameter while it was 10.5 um (7.3-13.5) wide, twice that of T. ctenophorii. T. nigra (Lom, 1960) from the skin of the host Cyprinus carpio, were reported to be larger (55.6 um cell diameter) and had a larger border membrane (5 um) and more pins per denticle (9-11), but fewer denticles (24.5 (21-30)), and again a dark center. The T. nigra macronucleus was 37 um (31.2-42.6) in diameter but 5.7 um (4.2-7.3) wide. It denticles were similar to T. ctenophorii in size and shape. Denticular morphology in T. hypsilepis (Wellborn, 1967) from the body and fins of a high scale shiner, Notropis hypsilepsis, was quite distinct from that of T. ctenophorii. It too had falcate blades and long, narrow thorns; however, both were pointed instead of blunt-tipped, and larger. The blades were 5.3 um (5-6), the thonrs 8 um (7-9), and the knob 2.6 um (2-3). In addition the number of pins per denticle, the overall body, denticular ring, and adhesive disk were all approximately twice the size. However, the adhesive disk of T. hypsilepsis is cup-shaped in stead of flat and the border membrane was also 4-4.5 um wide. The macronucleus was 40 um (35-46) in diameter and its width 5-6 um. The contractile vacuole was also located in the center of the oral surface in T. hypsilepis, whereas it was located inside the overlap of the adoral ciliary ring in T. ctenophorii. Finally, the adoral ciliary wreath overlaps to a lesser extent (370-380 degrees) than in T. ctenophorii. The only other trichodinid we are aware of with five pins per denticle is T. microdenticula from the body and gills of a shad host, Dorosoma petenense (Wellborn 1967). It was smaller, with a 26 um (22-37) diameter body, but a border membrane of 2 um (1.5-2.5), much like T. ctenophorii. The T. microdenticula adhesive disk was only 13 um diameter (12-15.5) with fewer denticles (16 (15-18)). Denticular morphology was truncated instead of falcate and the horns unusually short (1.9 um (1.5-2.0)), and again its center stained darkly with Klein's silver stain. One of the most distinct differences between the two species was the oral ciliary wreath, which in T. microdenticula wrapped only 330-350 degrees. The macronucleus was 17 um (13-22) in diameter and 2.5 um (2-3) wide. (ref. ID; 7416)
Type locality; Northern coast of the Gulf of Mexico, specifically Mobile Bay off Forts Gaines and Morgan, and from the mainland-to-island causeway that separates Apalachicola Bay and St. George Sound. (ref. ID; 7416)
Hosts; Mnemiopsis maccradyii and Beroe ovata. T. ctenophorii was observed to be attached primarily to the aboral side of auricular, subsaggital, and subtentacular comb plates. (ref. ID; 7416)
Type specimens; One silver-stained holotype slide specimen has been deposited with the International Protozoan Type Slide Collection, National Museum of Natural History, Smithsonian Institution, Washington, D.C., accession number USNM #47907. Remaining holotype specimens currently remain in the collection of AGM describing the microbial communities of ctenophores. (ref. ID; 7416)
Trichodina domerguei (Wallengren) (ref. ID; 1618) reported author and year? (ref. ID; 3292), domerguei domerguei (ref. ID; 4610, 4613)
Description; Discoid, slightly constricted; adoral spiral complete, 35-50 um in diameter; macronucleus sausage-shaped with a single micronucleus; denticulate ring with denticles with long curved hooks (20-34) and medium long rays which do not reach the center of the adhesive disc (variations occur). (ref. ID; 1618)
Measurements; Diameter 40-70 um; height 35-60 um. (ref. ID; 1618)
Trichodina myicola Uzmann & Stickney, 1954 (ref. ID; 1618)
Description; Bell-shaped to discoid; two parallel adoral rows of cilia, forming "semi-membrane"; number of denticles 26-36; on the oral region of the marine bivalve, Mya arenaria. (ref. ID; 1618)
Measurements; Average diameter 81 um; height 31-86 um; diameter of the denticulate ring 29-46 um; diameter of the basal disk 42-79 um. (ref. ID; 1618)
Trichodina nigra Lom, 1961 (ref. ID; 4764) reported author and year? (ref. ID; 2459, 7719)
Description; Ultrastructural study. (ref. ID; 7719)
Trichodina pediculus (O.F. Muller) (ref. ID; 1618), (O.F. Muller, 1786) Ehrenberg, 1830 (ref. ID; 1219, 1620, 1629) reported year? (ref. ID; 5462)
Syn; Trichodina baltica Quennerstedt, 1869
Description; Body discoid, often with a median constriction; adoral spiral complete, describing an arc of more than 360 degrees (35-45 um in diameter); sausage-shaped macronucleus; a single micronucleus; adhesive disk with a denticulate ring consisting of denticles (22-25) with curved hooks and long rays extending to the middle of the disk; on Hydra and on the gills of Necturus and Triturus larvae, although Raabe considers Hydra the sole host. (ref. ID; 1618)
Measurements; Diameter 35-60 um, height 25-55 um; adhesive disk 27.5-47.5 um in diameter. (ref. ID; 1618)
Trichodina sphaeronuclea Lom, 1956 (ref. ID; 4059)
Description; Lom reported as an ectozoid from the slime beneath the mantle of slugs. (ref. ID; 4059)
Trichodina urinicola Fulton (ref. ID; 1618) reported author and year? (ref. ID; 3292)
Description; 28-36 hooks; 26-31 denticles; ray fuse with central argentophile area; in the urinary bladder of various amphibians. (ref. ID; 1618)
Measurements; Body small in diameter; 50-90 um high; diameter adhesive disk 30-55 um; diameter of denticulate ring 18-30 um. (ref. ID; 1618)