The influence of temperature change on number of anal fin rays developing in Fundulus majalis (Walbaum)

Abstract

In each of two experiments embryos of this cyprinodont fish were reared continuously in four fluctuating temperature regimes, 13°–17°, 18°–22°, 23°–27°, and 28°–32°C to determine response of presumptive anal fin-ray tissue to temperature change. Because of excessive mortality among embryos in the 13°–17°C temperature regime, only one transfer lot from this regime could be used. In both experiments a positive linear relationship was indicated between mean anal fin-ray count and temperature, more anal rays developed on the average with increasing temperatures. In one experiment the transfer of embryos from one of the cooler regimes to the warmest at a three-to-six-somite stage of development produced a mean anal fin-ray count similar to that of embryos reared continuously in the warmest regime, but significantly different from the mean of those reared continuously in the original cool regime. The transfer of embryos from one of the cooler regimes to the warmest at a nine-to-twelve-somite stage produced a mean anal fin-ray count similar to that of embryos reared continuously in the cooler regime, but significantly different from the mean of those reared continuously in the warmest regime. In regard to morphological time of fixation of anal fin-ray tissue in this species temperature can influence the number of anal fin rays at the three-to-six-somite stage of development; although the nine-to-twelve-somite stage showed no response to temperature influence, later stages may be sensitive.