Influences of light-dark cycle and water temperature on in vitro egg laying, hatching, and survival rate of the Thaparocleidus vistulensis (Dactylogyridea: Ancylodiscoididae).

The European catfish (Silurus glanis) is an important species with high economic value, and its growing demand has led to intensive farming practices for it. However, this species is increasingly challenged by parasitic infections, particularly from a specific gill monopisthocotylan parasite called Thaparocleidus vistulensis. To establish effective management strategies, it is crucial to comprehend the fundamental environmental variables that could influence the reproductive and survival behavior of T. vistulensis. The present study conducted controlled in vitro experiments to observe the fecundity, hatching rate, and survival ability of T. vistulensis under varying light-dark conditions, as well as across a range of water temperatures from 5 to 35 °C. Interestingly, light exposure led to a threefold increase in egg production by adult T. vistulensis compared to constant darkness. While light or dark conditions did not significantly affect the hatching and survival rate of adults, they did significantly affect the survival rate of oncomiracidia. The parasite's fecundity was optimal at 15 °C. Eggs hatched fastest at 30 °C, whereas no hatching occurred at 5 °C and 35 °C. The survival rate for both oncomiracidia and adults showed a negative correlation with increasing water temperatures. These findings provide fundamental insights into how varying environmental variables impact the life cycle of the parasite. The improved understanding of these findings provides a valuable basis for the management of T. vistulensis in cultured European catfish stocks in fish farms.