Temperature-induced ontogenetic plasticity in sea bass (Dicentrarchus labrax)

We studied the ontogeny of Dicentrarchus labrax comparatively under constant rearing temperatures of 13, 15 and 20°C. At hatching, yolk-sac larval morphometry differed significantly between the temperatures and especially between the two extremes, while at the end of the yolk-sac larval stage, it mainly differed between the two lower temperature regimes and that of 20°C. Compared with the two lower temperature conditions, at 20°C D. labrax presented a significant ontogenetic acceleration which was morphologically expressed either as a significantly smaller total length (TL) at feeding onset, notochord flexion and fin differentiation, or as shifts of the allometric inflection points of 8 out of the 15 morphometric characters studied. Additionally, temperature significantly affected the allometry coefficients, with a decreasing growth intensity as the temperature difference decreased. The rate of TL growth increased under elevated temperature conditions throughout the entire ontogenetic period, except during the early larval period (feeding onset to metamorphosis onset), at which time D. labrax presented equal growth rates at 15°C and 20°C. The results are discussed with respect to the ontogeny of the functional morphology and the meanings of temperature- induced ontogenetic plasticity for the survival of fish larvae.