Trichodina corydori, S. MARCOTEGUI & Basson & R. MARTORELLI, 2016

S. MARCOTEGUI, Paula, Basson, Linda & R. MARTORELLI, Sergio, 2016, Trichodinids (Ciliophora) of Corydoras paleatus (Siluriformes) and Jenynsia multidentata (Cyprinodontiformes) from Argentina, with Description of Trichodina corydori n. sp. and Trichodina jenynsii n. sp., Acta Protozoologica 55 (4), pp. 249-257 : 250-252

Trichodina corydori n. sp. ( Figs 1A–D ; 4A )

Description. A small to medium-sized, freshwater trichodinid: body diameter, 33.9–42.3 (38.1±2.5); adhesive disc diameter, 27.7–37.0 (32.1±2.6); diameter of denticulate ring, 16.2–23.3 (20.4±1.7); width of border membrane, 1.8–3.3 (2.9±0.4); denticle number, 23–27 (24); number of radial pins per denticle, 8–10 (10); denticle span, 8.0–10.7 (9.2±0.7); denticle length, 2.8–4.7 (3.8±0.6); central zone of adhesive disc dark; blade length, 3.4–4.4 (3.8±0.2). Anterior blade margin strongly rounded, curving into very prominent blade apophysis. Distal margin of blade rounded with blade filling most of space between Y-axes. Distal blade margin with strong curve towards blunt and rounded tangent point. Apex of blade not touching Y+1 axis. Posterior blade margin shallow, becoming deeper towards central part. Section connecting the blade and central part short, but well developed. Central part well developed with rounded tip, fitting tightly into preceding denticle. Central part extending more than halfway to Y-1 axis. Shape of central part above and below the X-axis very similar. Central part width 1.0–1.9 (1.4± 0.3). Rays strongly developed, starting more narrow from central part, becoming slightly thicker towards proximal ends. Some rays directed towards center of adhesive disc, some angled slightly anteriorly. Ray apophysis not visible. Ray connection not well developed. Point of ray bluntly and strongly rounded. Ray length 3.5–5.1 (4.2±0.4). Ratio of denticle above to denticle below x axis 0.8–1. Adoral ciliary spiral makes a turn of 370–380°. Macronucleus horseshoe-shaped, elongated, external diameter is 30.7–34.3 (32.5±1.8), distance between ends 6.2–7.7 (7.1±0.6). Micronucleus not observed.

Type host: Corydoras paleatus Jenyns, 1842 ( Siluriformes : Callichthyidae )

Type locality: Samborombón River (Brandsen), Buenos Aires, Argentina (35°10′39.79″S, 58°15′29.70″W)

Site of infection: gills

Type specimens: MLP-Pr 98

Etymology: The specific epithet “corydori ” is coined from the name of host species.

Remarks. Morphological features of specimens found in C. paleatus agree with typical for Paratrichodina . Thus, denticles have well-developed rays, and are wedged together only by central parts, if anterior projection present, is situated near the base of the blade and is not in contact with the notch in the blade of the preceding denticle ( Lom 1958, Basson and Van As 1989). Lom and Haldar (1976) state that the upper limits of the adoral cilia in Trichodinella Šrámek-Hušek, 1963 , Tripartiella Lom, 1959 and Paratrichodina are 290°, and the lower limit in Trichodina is 330°. Nevertheless, the importance of the length of the adoral cilia as a generic characteristic sometimes appears to be less distinct than previously thought. Recently the majority of described species have in effect been classified based on denticle morphology alone ( Gaze and Wootten 1999). The adoral spiral in T. corydori n. sp. presents a turn of more than 330°, which falls in the range for Trichodina .

The denticle shape of T. corydori mostly resembles Paratrichodina africana Kazubski and El-Tantawy, 1986 recently reported from wild and farmed Oreochromis niloticus (Linnaeus) in eastern Amazonia, Brazil by Tavares-Dias et al. (2013). However, T. corydori differs from P. africana in the shape of the denticle, some other measurements, as well as the adoral spiral: (1) The new species is larger than P. africana , for example, in the adhesive disc (27.7–37.0 vs. 12.2–25), and denticulate ring (16.2–23.3 vs. 5.7–16.5). (2) In the case of the new species, the ray length is similar to blade length, but in the case of P. africana the ray is shorter than the blade. (3) The ray is thicker in the new species than in P. africana . (4) The section connecting the blade and the central part is very short in the new species, but long in P. africana . (5) The morphometric data of the new species also vary when compared to those of P. africana , e.g., blade length (3.4–4.4 vs. 1.5–3.8), ray length (3.5–5.1 vs. 0.5–2.1), denticle span (8.0–10.7 vs. 2.9–5.5).

This is the first report of a trichodinid from C. paleatus .

Figures

Fig. 1. Photomicrographs of Trichodina corydori n. sp. from Corydoras paleatus. A–B – Silver nitrate-impregnated adhesive discs. C – Methylene-blue staining of adoral ciliary spiral. D – and orcein stain of macronucleus. Scale bars: 10 μm.

Fig. 4. Diagrammatic drawings of denticles of trichodinids. A – Trichodina corydori n sp. from Corydoras paleatus. B – T. cribbi from Jenynsia multidentata. C – T jenynsii n sp. from J. multidentata. D – T. pediculus redrawn from Kazubski and Migala (1968). E – T. pediculus redrawn from Gaze and Wooten (1998). F – T. pediculus redrawn from Kazubski (1991c).