Temperature is the major abiotic factor controlling the rate of morphogenesis in fish. The present work investigated hatching time and the transition from endogenous to exogenous feeding at five constant temperatures over the range 1535°C. Clarias gariepinus eggs can be successfully hatched in ambient water tempcratures between 20 and 35"C, although at 30°C the hatching rate is significantly improved. At 15°C embryos do not survive. The period of hatching is inversely related to temperature such that synchronous hatching is encouraged by high temperature within the specific temperature range. The extent to which development rate and metabolic rate in C. gariepinus are accelerated by temperature is not the same. The duration between first feeding, yolksac absorption and the point-of-no-retum is inversely related to temperature. The same threshold temperature, below which development is theoretically arrested, can be estimated for C. gariepinus from the linear relationship between development rate and temperature up to hatching, first feeding and yolksac absorption. This closely approximates the lower lethal temperature of 15°C estimated directly from embryo survival. The effect of temperature can be usefully modelled in C. gariepinus using the linear relationship V = a + b t to estimate t« (threshold temperature) and D: , (effective day-degrees) and the hyperbolic relationship r = D:,l(tt,,) to determine development time. From the present work, t,, is 14.5"C and DC,, is 13, 26.3 and 35.7 for hatching, first feeding and yolksac absorption respectively for C. gariepinus. Unlike day-degrees, effective day-degrees remain independent of temperature over the range 20-35°C. An approximate guide to development time at different constant temperatures within this range is given.
HCG-induced (dose: 2 iu g-1 body weight) ovulated eggs of catfish (Clarias macrocephalus) remained viable for artificial fertilization up to 10 h post-ovulation without apparent significant loss in fertility. At 12 h post-ovulation viability decreased significantly, showing little or no hatching at 20 h. A limit of 10 h between ovulation and egg-stripping was suggested for this species at an ambient temperature of 26-3 I" C.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.