Claw morphology and influence on feeding electivity of four Pacific Northwest crab species

Abstract

Crabs use their claws for a number of uses including handling and processing of prey items. However claws are not uniform across species, they show a number of variations including those in their denticle patterns. To investigate these variations individuals from the species Glebocarcinus oregonensis, Chionoecetes bairdi, Pugettia producta, and Oregonia gracilis were collected and the morphology of the crabs’ claws were measured. The measurements included the radius of curvature of the denticles and distance of these denticles along the claw. From these measurements we made predictions about potential prey type preference for each species. To test these predictions the crabs were put through choice and no choice feeding trials. Food types tested included kelp, snail, and shrimp species. We found that all the crab species in this study showed difference in their claw morphologies as well as their feeding preferences. G. oregonensis showed a preference for snails while the other species consumed more shrimp or kelp. However despite these differences all four species consumed shrimp as a first or second choice.