Morphology and gametic compatibility of color morphs of Paracentrotus gaimardi ( Echinodermata: Echinoidea).

Five color morphs of Paracentrotus gaimardi can be distinguished along the coast of Rio de Janeiro, Brazil: black, brown, gray, green, and pink. All co-occur and are apparently exposed to similar environmental conditions. This study compares the morphology of these color morphs and investigates their gametic compatibility. All specimens of the five color morphs matched earlier descriptions of the species. The number of lateral spines on globiferous pedicellariae, the presence of small ophicephalous pedicellaria, and the pattern of distribution of pedicellaria on the test were reliable morphological characters for taxonomic purposes. The five color morphs were not clearly differentiable in terms of morphology. Fertilization success in crosses within color morphs was greater than in the majority of heteromorphic crosses. Only three heteromorphic crosses - ♀gray and ♂brown, ♀black and ♂gray, and ♀brown and ♂black - were as successful as control, within-color morph crosses. Therefore, some color morphs seem to be partially isolated by an incipient barrier to fertilization. Low fertilization rates among color morphs should result in genetic divergence among them. In fact, genetic divergence at bindin and ATPase genes has been reported among color morphs of P. gaimardi. Natural selection seems to favor fertilization within color morphs, but the mechanism for this differentiation in gametic compatibility is not known. [ABSTRACT FROM AUTHOR]