RESUMEN
This study aimed to examine the prevalence of Ichthyophthirius multifiliis in fish inhabiting natural water bodies in the Lhasa and Nagqu regions of Tibet in September 2020 and August 2021. The results showed that Schizopygopsis selincuoensis had the highest prevalence of I. multifiliis at 33.73% (56/166), followed by Triplophysa tibetana at 30.00% (6/20), Triplophysa brevicauda at 27.91% (12/43) and Schizopygopsis thermalis at 23.66% (31/131). No infection with I. multifiliis was observed in exotic fish species. In addition, the prevalence of I. multifiliis in Boqu Zangbo (river), Selincuo Lake and Cuona Lake in the Nagqu region was found to be significantly higher than that in Lalu Wetland and Chabalang Wetland in the Lhasa region (P < 0.05). The study revealed a significantly lower prevalence in Lhasa River than in Cuona Lake (P < 0.05). Notably, our findings revealed instances of I. multifiliis infections even in saline water bodies, thereby emphasizing the potential threat that this parasite poses to the preservation of indigenous fish resources in Tibet. Consequently, immediate and effective countermeasures are imperative. This study represents the first systematic investigation of I. multifiliis infection in natural water bodies in Tibet.
RESUMEN
The rare minnow Gobiocypris rarus is an ideal model organism for toxicological research. Dactylogyrus species are usually found on the gills of this rare minnow in laboratory farming systems. Dactylogyrid infection may change the sensibility of fish to toxicants and affect toxicological evaluations. In the present study, dactylogyrid infection was investigated, and species of Dactylogyrus collected from rare minnows were determined. Based on the observed 'D. wunderi' type anchors, with a shorter outer root and elongated inner root, and accessory piece consisting of two parts, the dactylogyrids were identified as D. gobiocypris. A partial 18S-ITS1 rDNA sequence was firstly sequenced, and the highest sequence identity (86.7%) was to D. cryptomeres. Phylogenetic analysis revealed that D. gobiocypris formed a clade with D. squameus, D. finitimus, and D. cryptomeres, all of which have been recorded in the family Gobionidae. Histopathology analysis indicated that a heavy burden of D. gobiocypris caused necrosis of gill filaments. Inflammatory responses, such as tumefaction and hyperaemia, were also observed on gills with severe dactylogyrid infection. Supplementary morphological characteristics and 18S-ITS1 rDNA sequence provided basic data for identification of this parasite species.