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

The effect of temperature (15, 18 and 21 degrees 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 degrees 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 degrees C, respectively) and wet body mass (14.7, 51.9 and 106.43 mg at 15, 18 and 21 degrees C, respectively) were significantly different. The dependency of daily weight specific growth rate (G; %day(-1)) on temperature (T; degrees C) was explained by the function: G = -32.905 + 2.8079 T - 0.00166 T-3. Three development scales were compared for temperature-dependency: chronological time (days), day-degrees (D degrees) and effective day degrees (D-eff degrees). It was demonstrated, within a viable temperature range, the suitability of D-eff degrees 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 degrees C were constructed. D-eff degrees 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 degrees+0.0037 D-eff degrees(2)-0.000006 D-eff degrees(3). 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 degrees C are recommended for the rearing of this species in captivity. (C) 2012 Elsevier B.V. All rights reserved.