Shape Changes and Growth Trajectories in the Early Stages of Three Species of the Genus Diplodus (Perciformes, Sparidae)

ABSTRACT The larvae of three species of the genus Diplodus (Diplodus vulgaris, D. sargus, and D. puntazzo) colonize shallow waters along the Mediterranean coasts and, after a short period spent in the water column, they settle. For all three species this habitat transition is characterized by important shape changes mostly related to swimming capacity and feeding behavior. In this study, geometric morphometrics are used to characterize shape changes during the early juvenile life of specimens collected in a single locality in order to compare growth curves and allometric relationships. Size-related shape changes proved to be similar for all three species and are consistent with the ecological transition. A nonparametric smoothing technique (Loess) was used to fit the scatter of shape on size. The graphical representation (of most sizerelated shape variability) of this fitting technique shows how major shape changes are rapid for small sizes and slow down successively. The approach allows for the visualization of allometry and the fitting technique might help in defining the allometric growth pattern, thus contributing to the study of the autoecology of the species and in establishing terms for comparison with other ecologically or phylogenetically related species. J. Morphol. 250: 24 -33, 2001. © 2001 KEY WORDS: geometric morphometrics; fish ecology; ecomorphology The three species of sea bream, the common twobanded sea bream Diplodus vulgaris, the white sea bream D. sargus, and the sharpsnout sea bream D. puntazzo, are marine teleosts widely distributed in Mediterranean coastal waters. In common with other marine littoral fish species, their life cycle involves a pelagic dispersal larval phase followed by a sedentary benthic adult phase In this study, geometric morphometric