Carapace relative growth of Trapezia Latreille, 1828 (Decapoda, Brachyura), crabs that are symbionts of hard corals, from Clipperton atoll and the Revillagigedo islands: ecological and zoogeographical implications

• Published in: Crustaceana 2010-01, Vol.83 (11), p.1371-1383
• Main Authors: Sanvicente-Añorve, Laura, Hermoso-Salazar, Margarita, Solís-Weiss, Vivianne, Salgado-Ugarte, Isaías
• Format: Article
• Language: English
• Subjects: Bidentata; Brachyura; Coral reefs; Corallina; Corals; Crabs; Decapoda; Digitalis; Larvae; Larval development; Metapopulation ecology; Population characteristics; Population ecology; Population growth; Symbionts; Trapezia
• ISSN: 0011-216X; 1568-5403
• DOI: 10.1163/001121610X533520

Decapod metapopulation dynamics are better understood by confronting theoretical studies with empirical data. In this study, our goal was to analyse the morphometric characteristics and relative growth of the carapace of Trapezia bidentata (Forskål, 1775) and T. digitalis Latreille, 1828, crabs from the islands Clipperton and Revillagigedo, in order to assess the degree of inter-and intraspecific similarity of the four insular populations. We examined 325 specimens and identified four species: T. bidentata (72.9% of total abundance), T. digitalis (23.1%), T. formosa Smith, 1869 (3.4%), and T. corallina Gerstaecker, 1857 (0.6%). Three carapace measurements were taken for each specimen: carapace width (CW), carapace length (CL), and interocular distance (ID). The variables CL and ID were fit to a power equation taking CW as the reference dimension. As in other brachyurans, growth pattern analyses indicated an isometric type in all CW vs CL and CW vs ID relationships examined. Interspecific differences included a larger body size for T. bidentata and larger ID/CW for T. digitalis. Significant intraspecific differences in the two insular populations of T. digitalis were evidenced in the ID/CW ratio. In contrast, populations of T. bidentata were morphometrically closer. These results indicate a higher degree of connectedness of the parts of the T. bidentata metapopulation than of that of T. digitalis, probably due to differences in the duration of their larval stages. We think that the larger body size in T. bidentata might account for competitive advantages in food gathering and habitat selection over the remaining species. In turn, as a counteracting trait for its smaller size, the larger ID might allow T. digitalis a better ability to perceive 3D and to judge relative distances between objects, thus avoiding competitive combats and improving antipredatory or escape responses. La dinámica de las metapoblaciones de decápodos se comprende mejor confrontando estudios teóricos con datos empíricos. En este estudio, nuestro objetivo fue analizar las características morfométricas y el crecimiento relativo del caparazón de Trapezia bidentata (Forskål, 1775) y T. digitalis Latreille, 1828, cangrejos de las islas Clipperton y Revillagigedo a fin de determinar el grado de similitud inter-e intraespecífica de las cuatro poblaciones insulares. Se examinaron 325 especímenes e identificaron cuatro especies: T. bidentata (72.9% de la abundancia total), T. digitalis (23.1%),