Evidence that temperature change cues reproductive development in the spiny damselfish, Acanthochromis polyacanthus

The role of temperature in the reproductive development of the spiny damselfish, Acanthochromis polyacanthus, was assessed by measuring changes in ovulatory periodicity and plasma levels of gonadal steroids in response to temperature shifts of 4degreesC. This was assessed in sexually mature, paired and unpaired fish. The effect of brood presence on reproductive activity was also assessed. Temperature change but not brood presence significantly affected the spawning periodicity of sexually mature, reproductively active pairs. A temperature increase from 24degreesC to 28degreesC resulted in a decrease in the ovulatory period from 32 days to 21 days. Incubation temperature was found to dramatically affect survival of the egg clutches with only one of 13 egg clutches surviving to hatching at 24degreesC, compared with 50 of 51 egg clutches surviving at 28degreesC. Gonadal steroid production was positively correlated with temperature increase in paired fish. Plasma levels of 17beta-estradiol and testosterone (T), increased significantly in female fish, whereas there was no change in T and 11-ketotestosterone, in paired male fish exposed to a temperature increase from 24degreesC to 28degreesC. In unpaired fish, temperature change had ambiguous affects on plasma steroid levels, suggesting that social context is necessary for stimulation of reproductive development by temperature.