INTRASPECIFIC STUDY OF TRICHODINELLA MYAKKAE (MUELLER, 1937) ŠRÁMEK-HUŠEK, 1953 BASED ON THE CHARACTERISTICS QUANTIZATION OF ADHESIVE DISC

Trichodinids (Mobilida: Trichodinidae), best known as ectoparasites of fishes and mollusks in the aquaculture, are diverse and widely distributed mobilid ciliates. So far, approximately 400 species representing 10 genera have been described around the world. Among them, Trichodinella species is almost one of the smallest groups in the family Trichodinidae. Trichodinella myakkae (Mueller, 1937) Šrámek-Hušek, 1953, regarded as the representative of Trichodinella species, was often found to infect different freshwater fishes and sometimes caused economic losses when those fish fingerlings or fries were heavily infested in the aquaculture. Currently, most studies about trichodinds were focused on the species description and identification, geographic distribution, histopathology, biodiversity, and molecular phylogeny. However, the morphology study has become the solid foundation to hold up the above related studies on trichodinids. In terms of morphological taxonomy, the adhesive disc is regarded as the most important structure for trichodinids. Therefore, based on the characteristics quantization of adhesive disc, intraspecific study of Trichodinella myakkae isolated from three different hosts (Hypophthalmichthys molitrix, Aristichthys nobilis and Pseudorasbora parva) were firstly carried out by using morphological and statistical ways in the present work. The results showed that three populations of Trichodinella myakkae (from Hypophthalmichthys molitrix, Aristichthys nobilis and Pseudorasbora parva,), the P values were 0.136 (P>0.05) for diameter of body diameter, 0.009 (P<0.01) for diameter of adhesive disc, 0 (P<0.01) for diameter of denticular ring and 0 (P<0.01) for denticle span, respectively. Meanwhile, the P value of ratio of denticular ring to body diameter was 0 (P<0.01). In addition, the result of correlation analysis displayed that the significant positive correlation (P<0.01) existed between the diameter of body and adhesive disc, denticular ring diameter and denticle span, and no significant correlation (P>0.05) existed between width of border membrane and the other structures in the adhesive disc. All the above results indicated that significant differences existed in diameters of adhesive disc and denticular ring, denticle span, and the ratio of diameter of denticular ring to body diameter except the body diameter for the three populations, ameng which the population of Hypophthalmichthys molitrix was the largest population. The correlation analysis indicated that body diameter was primarily affected by adhesive disc, and vice versa. The diameter of denticular ring was primarily affected by denticle span, and vice versa. The denticle number was primarily affected by the diameter of adhesive disc. The width of border membrane wasn’t affected by the related structures in the adhesive disc. In conclusion, it was indicated that the significantly differential adhesive disc structures above could be used for the species identification in the taxonomy of trichodinds based on the present research results.