Geographic differences in the carapace shape of the crab Cyrtograpsus affinis (Decapoda: Varunidae) and its taxonomic implications
Aníbal H. Lezcano, Rolando González-José, Eduardo D. Spivak and Fernando G. Dellatorre

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.

Keywords: Cyrtograpsus altimanus, allometry, geometric morphometrics, Río de la Plata estuary, Nuevo Gulf, local adaptations, contrasting habitats.
Contents of this volume Sci. Mar. 76(2) : 329-337 Back PDF
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