Trichodina nigra, Lom, 1961

Yuryshynets, Volodymyr, Ondračková, Markéta, Kvach, Yuriy & Masson, Gérard, 2019, Trichodinid Ectoparasites (Ciliophora: Peritrichia) of Non-native Pumpkinseed (Lepomis gibbosus) in Europe, Acta Protozoologica 58 (2), pp. 69-79 : 73-75

Comparisons between Trichodina nigra and congeneric species

Analysis of biometric indices demonstrates similarity between the species compared in different descriptions ( Trichodina mutabilis Kazubski et Migala, 1968 , Trichodina kazubskii Van As et Basson, 1989 , T. nigra and T. tumefaciens ), which is common for Trichodina species ( Van As and Basson 1989). Out of the species compared, the new species exhibited maximum similarity to T. nigra with shorter length of the central part of a denticle as the only significant difference in metric data available from description of T. nigra in Bauer 1984 ( Table 1). Denticle morphology allows identification of differences between Trichodina lepomi n. sp. and T. nigra and other congeneric species such as T. mutabilis and T. kazubskii , as follows ( Table 2):

A) absence of posterior projection of blade ( T. nigra , T. mutabilis );

B) absence of notch/ indentation opposing ray apophysis ( T. nigra , T. mutabilis , T. kazubskii );

B) absence of ray apophysis ( T. nigra , T. mutabilis ,

T. kazubskii );

C) blade is not displaced anteriorly relative to ray as significantly as in T. nigra .

Some specimens of Trichodina lepomi have a prominent border between the anterior and posterior parts of denticle, probably due to their different thicknesses. The border reaches the blade apophysis (see Fig. 3A). Posterior margin of blade is clearly defined; anterior margin is often partially impregnated.

Trichodinids reported from the centrarchids and, in particular, representatives of the genus Lepomis in North America, include T. tumefaciens ( Li and Desser 1985, McDonald and Margolis 1995) and T. fultoni (Hofmann and Lom 1967) . Measurements of T. tumefaciens used for comparison with our specimens ( Table 1) were taken from species described from the North American mottled sculpin, Cottus bairdi Girard, 1850 ( Wellborn 1967), as metric characteristics from pumpkinseed are not available ( Li and Desser 1985) and exhibit significant differences in many features (Table 1). Nevertheless, this species is not mentioned in the main summary articles and keys devoted to trichodinids ( Lom and Dyková 1992, Bauer 1984, Van As and Basson 1989, Basson and Van As 1994), casting doubt on its validity. Metric data of Trichodina fultoni were not included in analysis as this species has a more distinguishable difference in morphology – light central zone of adhesive disk.

Slight differences in denticle morphology reflect on- togenetic variability. Some intra-population variability has been confirmed for T. lepomi sp. n. from different localities and host-individuals; however, all differences correspond to parameter ranges in comparative diagnoses.