The influence of temperature on the embryonic development of the annual fish Cynopoecilus melanotaenia (Cyprinodontiformes, Rivulidae).

The present study aims to provide data about the time required for Cynopoecilus melanotaenia kept at different temperatures to complete embryonic development. This information can be valuable for optimizing laboratory culture and facilitating future use of this species as a test organism in toxicity tests. Temperature effects on hatching rate are presented as well as information related to embryonic development stages. Eggs were observed daily, from start to finish of embryonic development. Thirteen developmental stages were described. Eggs were kept at two constant temperatures (20 degrees C and 25 degrees C) and at a variable ambient temperature (16-25 degrees C-mean = 21 degrees C, sd = 1.95), to determine developmental rate (velocity) at each temperature. A shorter incubation period was necessary to complete development at 25 degrees +/- 1 degrees C. However, all embryos kept at this temperature hatched with morphological defects, which prevented their survival. No significant difference in developmental time period (p = 0.05) was observed at the 20 degrees C and 16 degrees-25 degrees C (mean = 21 degrees C, sd = 1.95) temperatures.