Synchronization in allometric and morphological changes during metamorphosis: comparison among four sparid species

Abstract

Understanding critical ontogenetic transitions in the life of fish, such as metamorphosis, is of prime importance for determining the factors that affect survival probabilities and control recruitment levels. Metamorphosis involves a plethora of changing characters and its definition requires a multi-parametric approach. In the present study, mean lengths (Lm) at allometric and morphological change during the transition from larval to juvenile phenotype were estimated with a recently introduced multi-character protocol and compared between Diplodus sargus (settling in spring), Oblada melanura (summer), D. puntazzo (autumn) and D. vulgaris (winter). Lm from allometry closely matched Lm from morphology in D. sargus and D. puntazzo but not in the winter- and summer-settling species, in which morphological transition occurred later or earlier than allometric change, respectively. Lm from allometry was very similar in the 3 Diplodus species but larger in O. melanura. The coefficients of variation of Lm from morphometric and morphological characters were negatively correlated. Morphological transitions were less synchronized but changes in allometric growth were more synchronized in D. vulgaris (winter) while the opposite was true for O. melanura (summer). This study highlights for the first time the relative importance of taxonomic relatedness and season (temperature) in determining the size at metamorphosis and the degree of synchronization (abruptness of change) both within and between mensural and morphological characters.