Temperature-induced changes of growth and survival in the early development of the seahorse Hippocampus guttulatus

Abstract

The effect of temperature (15, 18 and 21 °C) on the early development of the long-snouted seahorse Hippocampus guttulatus were analysed, both under feeding (until day 30 post partum) and starving conditions. Fed and starving seahorses maintained at 15 °C grew at suboptimal conditions. At this temperature, mortalities started earlier and the swimming activity was reduced. In fed juveniles, final survivals (21.1, 85.9 and 81.1% at 15, 18 and 21 °C, respectively) and wet body mass (14.7, 51.9 and 106.43 mg at 15, 18 and 21 °C, respectively) were significantly different. The dependency of daily weight specific growth rate (G; % day− 1) on temperature (T; °C) was explained by the function: G = − 32.905 + 2.8079 T − 0.00166 T3. Three development scales were compared for temperature-dependency: chronological time (days), day-degrees (D°) and effective day degrees (D°eff). It was demonstrated, within a viable temperature range, the suitability of D°eff as a temperature-independent scale to quantify growth in feeding juveniles but not in starving conditions. Seahorse wet weight was modelled as a function of time scales and temperature according to a modification of the Gompertz model. Growth models for single temperatures in the range of 14–26 °C were constructed. D°eff was the only scale that allowed a good temperature-independent fitting of seahorse weight (W; mg) in a unique equation: W = 7.409 − 0.0555 D°eff + 0.0037 D°eff2 − 0.000006 D°eff3. Biological, ecological and biogeographic implications of temperature in the early development of the viviparous fish H. guttulatus are discussed. Finally, from a practical point of view, temperatures of 19–20 °C are recommended for the rearing of this species in captivity