Trichodina subtilihamata, Tang & Zhao & Tao, 2007

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 : 40-42

Trichodina subtilihamata sp. nov.

( Figs. 1A–B , 3A )

Type-host: Carassius auratus .

Location: Gills.

Prevalence: Out of 21 fishes examined, one was infected (4.8 %).

Type-locality: Chongqing (29º5' N, 106º5' E), China .

Date of sampling: March, 2004.

Type-specimens: Syntypes, slide No. CQJ-03-01 and CQJ-03-02, deposited in the collection center of the Key Laboratory of Animal Biology of Chongqing, Chongqing Normal University, China .

Etymology: The name “ subtilihamata ” refers to the conspicuous morphological feature (thin-hooked blade) of the trichodinid, and it is a composite of the Latin prefix “ subtili -” (= thin, slender) and the Latin suffix “ hamata ” (= hook).

Description. Medium-sized. Body diameter 50.0–56.0µm (52.2 ± 3.1). Diameter of adhesive disc 38.0– 48.0µm (42.3 ± 3.7). Center of disc clear and without any granules. Border membrane 4.0–5.0µm (4.6 ± 0.3) in width. Diameter of denticulated ring 26.0 - 30.0µm (28.2 ± 1.7). Number of denticles about 26–29 (n = 16). Number of radial pins (mode) per denticle 10–12 (n = 16). Span of denticle 13.0–17.0µm (15.6 ± 1.7). Length of denticle 5.0–7.0µm (5.6 ± 1.3). Blade shape slender, 5.0–6.0µm (5.4 ± 0.5) in length. The anterior blade surface concave and forming an S-shape, not extending past Y+1 axis. Apex of blade absent. The posterior surface forming arch curve with deepest point of blade, and not parallel to anterior blade surface. Distal blade surface smooth and relatively straight, lower than tangent point. Apophysis of blade present but the posterior projection absent. Blade connection relatively broad. Central part well developed with rounded point fitting tightly into preceding denticle, just extending about half way to Y-1 axis. Shape of central part above X axis similar to the part below. Width of central part 2.0–3.0µm (2.3 ± 0.6). Ray connection short but stumpy, inconspicuous and barely distinguishable from ray. Ray thin, smooth and needle-shaped, tapering gradually to sharp point and directed forward, tip of ray almost touching Y+1 axis. Ray apophysis not prominent and length of ray 5.0–8.0µm (6.6 ± 1.7). Ratio between denticle above and below X axis about one. Adoral ciliary spiral turns about 370º–390º around peristomial disc. Macronucleus U-shaped, and micronucleus spherical, situated in –Y1 position.

Remarks. The present trichodinid species is mainly characterized by possessing a slender blade with Sshaped anterior hooked blade surface. Based on the overall shape of the adhesive disc, the new species differs significantly from other known trichodinid species and only shows some resemblance to Trichodina nobilis Chen, 1963 ( Chen, 1973) . However, these two species also show some obvious differences ( Figs. 3A, B ) as discussed below.

In terms of the morphometric data in both trichodinids, T. nobilis Chen, 1963 differs from the new species mainly in three important points: firstly, T. nobilis is a large trichodinid (75–100µm), whereas the present species is medium-sized (50–56µm); secondly, the number of denticles are different (25–26 vs. 26–29); thirdly, the number of degrees of turn of the adoral ciliary spiral around the peristomial disc is different (390º –400º vs. 370º–390º).

In addition, although the shapes of central part and ray in of both species are similar, the morphological difference of blade is distinct. In terms of morphology of blade, the new species has very obvious differences from T. nobilis . The blade of T. subtilihamata n. sp. is biconcave as a result of the concave anterior blade which is an S-shape. In most cases, the anterior blade surface extends Y+1 axis and apophysis of blade is prominent; whereas these structures in T. nobilis are distinctly different: the blade is fan-shaped, anterior blade surface just touches the Y+1 axis, and there is no obvious apophysis of blade. According to the comparison with the related species, T. subtilihamata is considered to be a new member of the genus.

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.