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Variations in crab claw morphology and diet across contrasting inter‐tidal habitats
Authors:Ana C. F. Silva  Maryam Shapouri  Rui Cereja  Awantha Dissanayake  Catarina Vinagre
Affiliation:1. CERIS, DECivil, Instituto Superior Técnico, Universidade de Lisboa, Lisbon, Portugal;2. Faculdade de Ciências, Centro de Oceanografia, Universidade de Lisboa, Lisbon, Portugal;3. School of Biological Sciences, Plymouth University, Plymouth, Devon, UK
Abstract:Crabs are important predators of inter‐tidal ecosystems, controlling the abundance and distribution of their prey populations. Often the same crab species occupies several habitats and, although their effects on prey have been quantified across habitats, crabs’ dietary and morphological responses to differing environmental influences have been overlooked. Here, we used the crabs Eriphia verrucosa and Pachygrapsus marmoratus as model species to examine differences in claw morphometry – size and wear – and diet between rocky shore and heterogeneous sand flat habitats. We predicted that, intra‐specifically, crabs from rocky shores would consume more hard‐shelled prey owing to their high availability and consequently, would display chelipeds with the following claw characteristics: a higher degree of claw damage, stronger musculature (higher propel height) and increased mechanical advantage (defined as the ratio of input lever length to output lever length) than crabs in the heterogeneous sand flat habitats. Sampling was performed in heterogeneous sand flat habitats and rocky shores of the Central Portuguese coast. For each crab species, carapace width, diet composition and several claw morphometric measures were recorded, revealing significant intra‐specific differences (using multivariate analysis) between shore types. We found that E. verrucosa and P. marmoratus consumed more hard prey on rocky shore than on sand flat habitats, which resulted in rocky shore crabs having more accentuated dentition wear and larger musculature than their sand flat habitat counterparts. We suggest that the strong response of crab claw morphometry to environmentally induced diet variations is an important mechanism in the successful adaptation of crab species to inhabit differing habitats. A major implication is that the impact of the same species on prey may vary largely with habitat type as a result of predation efficiency varying with claw condition.
Keywords:Decapoda     Eriphia verrucosa     heterogeneous sand flat  intra‐specific variation     Pachygrapsus marmoratus     rocky shore
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