Marine Biology

, Volume 156, Issue 12, pp 2591–2599

Abundance, population structure and claw morphology of the semi-terrestrial crab Pachygrapsus marmoratus (Fabricius, 1787) on shores of differing wave exposure

Authors

    • Marine Biology & Ecology Research GroupUniversity of Plymouth
    • Marine Biological Association of the United Kingdom
  • Sónia Brazão
    • Laboratório Marítimo da Guia, Centro de Oceanografia da Faculdade de Ciências da Universidade de Lisboa
  • Steve J. Hawkins
    • Marine Biological Association of the United Kingdom
    • School of Ocean SciencesBangor University
  • Richard C. Thompson
    • Marine Biology & Ecology Research GroupUniversity of Plymouth
  • Diana M. Boaventura
    • Laboratório Marítimo da Guia, Centro de Oceanografia da Faculdade de Ciências da Universidade de Lisboa
    • Escola Superior de Educação João de Deus
Original Paper

DOI: 10.1007/s00227-009-1283-1

Cite this article as:
Silva, A.C.F., Brazão, S., Hawkins, S.J. et al. Mar Biol (2009) 156: 2591. doi:10.1007/s00227-009-1283-1

Abstract

Wave action is known to influence the abundance and distribution of intertidal organisms. Wave action will also determine the duration and suitability of various foraging windows (high-tide and low-tide, day and night) for predation and can also affect predator behaviour, both directly by impeding prey handling and indirectly by influencing prey abundance. It remains uncertain whether semi-terrestrial mobile predators such as crabs which can access intertidal prey during emersion when the effects of wave action are minimal, are influenced by exposure. Here, we assessed the effect of wave action on the abundance and population structure (size and gender) of the semi-terrestrial intertidal crab Pachygrapsus marmoratus on rocky shores in Portugal. The activity of P. marmoratus with the tidal cycle on sheltered and exposed shores was established using baited pots at high-tide to examine whether there was activity during intertidal immersion and by low-tide searches. Because prey abundance varies along a wave exposure gradient on most Portuguese shores and because morphology of crab chelipeds are known to be related to diet composition, we further tested the hypothesis that predator stomach contents reflected differences in prey abundance along the horizontal gradient in wave exposure and that this would be correlated with the crab cheliped morphology. Thus, we examined phenotypic variation in P. marmoratus chelipeds across shores of differing exposure to wave action. P. marmoratus was only active during low-tide. Patterns of abundance and population structure of crabs did not vary with exposure to wave action. Stomach contents, however, varied significantly between shores of differing exposure with a higher consumption of hard-shelled prey (mussels) on exposed locations, where this type of prey is more abundant, and a higher consumption of barnacles on sheltered shores. Multivariate geometric analysis of crab claws showed that claws were significantly larger on exposed shores. There was a significant correlation between animals with larger claws and the abundance of mussels in their stomach. Variation in cheliped size may have resulted from differing food availability on sheltered and exposed shores.

Copyright information

© Springer-Verlag 2009