Geographic differences in the carapace shape of the crab Cyrtograpsus affinis (Decapoda, Varunidae) and its taxonomic implications

ANIBAL LEZCANO,; GONZÁLEZ JOSÉ, ROLANDO; SPIVAK, ED; G DELLATORRE, FERNANDO

SCIENTIA MARINA

INST CIENCIAS MAR BARCELONA

Lugar: Barcelona; Año: 2012 vol. 76 p. 329 - 337

0214-8358

Cyrtograpsus genus was traditionally considered to be composed of three species: C. angulatus, C. altimanus and C. affinis. However, recent studies have found solid evidence suggesting that C. affinis and C. altimanus belong to a single species and hypothesize that the morphological differences which caused this misclassification could be related to different ecophenotypes or life stages. Here we report a geometric morphometrics study on the carapace shape of Cyrtograpsus specimens from the Río de la Plata estuary (36°S) and the Nuevo Gulf (42.75°S), testing for shape differences between different sizes (allometry) in the two environments. We found that previous morphological descriptions of the two species were associated with different sizes of a continuous, statistically significant allometric shape variation, concluding that C. affinis is a junior synonym of C. altimanus. We also found significant differences in the carapace shape between estuarine and marine environments, suggesting an effect of the environmental variables on carapace shape and a potential adaptive value of this trait.