Thermally-induced phenotypic plasticity in gilthead seabream Sparus aurata L. (Perciformes, Sparidae)

•Early water temperature determined the body-shape of juvenile S. aurata.•Body-shape variation concerned the relative position of skull and fin elements.•High temperature decreased the body size of larvae at certain ontogenetic events.

Finfish present a great ability to modify their phenotype in response to environmental conditions especially in the early ontogenetic period. Such plastic phenotypic responses have a great importance, from both the ecological and aquaculture point of view. The present study examined the effect of water temperature on the ontogeny and juvenile phenotype of Sparus aurata L. Six combinations of three temperatures (16, 19, and 22 °C) were applied during different phases of ontogeny up to the juvenile stage (ca 33–37 mm standard length, SL). Elevated temperature resulted in a relative acceleration of differentiation versus growth, which morphologically was evident as a significantly smaller SL (ca 11% decrease) at different ontogenetic events (development of fins, squamation and body shape). Moreover, geometric morphometric analysis clearly showed a significant effect of water temperature during early ontogeny on the juvenile body-shape. Thermally-induced variation of juvenile body shape was mainly expressed across the first canonical axis (56.4% explained variance), which discriminated the groups of highest temperatures from the rest. Water temperature mainly affected the position of the bases of supraoccipital and of basioccipital bones, of the upper jaw, as well as of the dorsal, anal and pelvic fins. The results are discussed with respect to the potential use of thermal manipulations during the hatchery phase to control the phenotype of S. aurata at the end of on-growing phase, i.e. at commercial size.