Effects of Salinity on the Egg Fertilization, Hatching, and Tadpole Growth and Survival Rates of the Thailand Frog (Rana tigerina Dubois, 1981)

Abstract

We studied the effects of salinity on the egg fertilization, hatching, and tadpole growth and survival rates of the Thailand frog (Rana tigerina Dubois, 1981), an introduced species that is commonly cultured in the Mekong Delta, Vietnam. Salinity levels of 2, 6, and 4% significantly affected the fertilization and hatching rates of the eggs, as well as the tadpole survival rates from the newly hatched to yolk sac exhaustion stages, respectively $\left(p<0.05\right)$. Notably, during the stage from yolk sac exhaustion to juvenile tadpole, a salinity of 3% resulted in an increase in the final weight of the tadpoles throughout the stage and a significant increase in Phase 1 (the tadpole stage from yolk sac exhaustion to the onset of foreleg emergence) and Phase 2 (the tadpole stage from the onset of foreleg emergence to the onset of hind leg emergence); however, it did not show a significant effect on tadpole survival rates in Phases 1 and 2 of this stage $\left(p>0.05\right)$. A salinity level of up to 5% showed no significant effect on the growth performance but caused a significant reduction in the survival rates of the tadpoles during this stage. We recommend that the artificial reproduction process of Thai frogs should be performed using salinities of <2%, with salinities of ≤2 and 3% being suitable for rearing tadpoles from the newly hatched to yolk sac exhaustion stage and from the yolk sac exhaustion to juvenile stage, respectively.