Trichodina nigra Lom, 1960

Tang, Fahui, Zhao, Yuanjun & Tao, Yanfei, 2007, Trichodinids (Ciliophora: Peritrichida) parasitic on gills of freshwater fishes, Carassius auratus and Aristichthys nobilis from China, with the description of Trichodina subtilihamata sp. nov., Zootaxa 1582 (1), pp. 39-48 : 43

Trichodina nigra Lom, 1960

( Figs. 1D , 3D )

Host: Carassius auratus .

Location: Gills.

Prevalence: Out of 16 fishes examined, one was infected (6.3 %).

Locality: Chongqing, China (29º5' N, 106º5' E) .

Date of sampling: February, 2004.

Description. Large-size, body diameter 65.0–73.0µm (69.6 ± 4.2); diameter of adhesive disc 49.0– 65.0µm (56.3 ± 3.4); border membrane 5.0–6.0µm (5.3 ± 0.3) in width; number of radial pins per denticle 10– 12 (n = 14); denticulated ring 28.0–34.0µm (31.6 ± 2.8) in diameter; number of denticles 28–32 (n = 14); span of denticle 18.0–20.0µm (19.2 ± 0.9); denticle 8.0–10.0µm (9.1 ± 0.8) in length; blade broad and sickleshaped, filling most of space between Y-axes; distal blade surface curved and smooth, always lower than tangent point; anterior surface curved and smooth, touching or almost extending to Y+1 axis; posterior margin forming shallow curve with deepest point at same level as apex; length of blade 7.0–8.0µm (7.3 ± 0.6), filling most of space between Y-axes; blade apophysis prominent whereas posterior projection invisible; central part well developed, 2.0– 3.0µm (2.3 ± 0.6) in width, extending more than halfway past Y axes; ray apophysis prominent; connection between central part and ray robust; length of ray 8.0–10.0µm (8.9 ± 1.2), ray long and slender and always parallel to Y axis; point of ray blunt and rounded; ratio of denticle above to below X axis always less than one. Macronucleus C-shaped, external diameter about 56; internal diameter about 44 and distance between terminations of macronucleus 14 approximately. Micronucleus oval, situated in +Y position. Adoral ciliary spiral turns about 380º –400º.

Remarks. Trichodina nigra Lom, 1960 is a parasite, the taxonomic status of which is dubious ( Van As & Basson, 1989). In the original description, this species comprises populations living on the skin, rarely on the gills of Cyprinus carpio, Scardinius erythrophtalmus, Rutilus rutilus , Abramis brama , Perca fluviatilis , Tinca tinca , Alburnus alburnus , Leuciscus cephalus and on the skin of different tadpoles in former Czechoslovakia. In the hosts mentioned above, all individuals of T. nigra agree in their principal characters, with an entire dark impregnated adhesive disc and without any clear area, so that there is no substantial diversity among them ( Lom, 1961). Later there are many other confusing descriptions of so-called T. nigra from different parts of the world since this species was first found ( Lom, 1961; Lom, 1970a; Stein, 1984). After that, those believed to be T. nigra , especially many subspecies of T. nigra , have been attributed to different species ( Lom, 1970a).

The dimensions and morphology of our specimens agree closely with those given by Lom (1961), generally falling within the range given in the description except for more radial pins per denticle in our population (10 – 12 vs. 8 – 10). T. nigra was ever found in South Bohemia, river Tisza, Hungary, Rybinsk Reservoir, USSR and South Africa ( Lom, 1961; Lom, 1970a; Arthur & Lom, 1984; Basson, et al., 1983). This is the first report for T. nigra in China and extends its geographic distribution in Asia.

Figures

FIGURE 1. Photomicrographs of silver impregnated specimens of Trichodina spp. A–B. Trichodina subtilihamata sp. nov; C: Trichodina uniforma Van As & Basson, 1989; D: Trichodina nigra Lom, 1960. Scale bar = 20m.

FIGURE 3. Diagrammatic drawing of the denticles of Trichodina spp. A–B. Trichodina subtilihamata sp. nov.; C: Trichodina uniforma Van As & Basson, 1989; D: Trichodina nigra Lom, 1960; E–F: Trichodina kazubski Van As & Basson, 1989; G–H: Trichodina mutabilis Kazubski & Migala, 1968.