Structure and distribution of carapace setae in British spider crabs

Abstract

Carapace setae were examined by SEM in species of spider crabs (Family Majidae). These setae are predominantly hamate (i.e. hooked), to which extraneous materials are attached for the purpose of concealment. They are described for eight species collected around the Isle of Man. In each species setae were sorted to types on the basis of consistent differences in size, shape and fine structure. Diversity ranged from two to six types per species, and this was examined in the context of their masking, or camouflage, habits. Certain setae can be assigned to particular species, so a limited taxonomic usage is indicated: however, further work is required for this to become a comprehensive tool. Distribution of setal types on the carapace is also described, and compared to patterns reported in previous studies.

Keywords:

• Carapace setae
• camouflage
• hooked setae
• Isle of Man
• spider crabs

Acknowledgements

We wish to thank C. J. Veltkamp, School of Biological Sciences, University of Liverpool, for all his help in producing the SEM images. Much gratitude to the late A. Deutsch who funded T.S. during this project.