Orchomene nanus (Krøyer) (Amphipoda: Lysianassoidea), a selective scavenger of dead crabs: feeding preferences in the field

Abstract

Simultaneously deployed multiple-trap rigs were proven to function replicably at a shallow-water (5–6 m) study site. A standard (crushed) bait of whole crabs [ Carcinus maenas (L.)] attracted significantly more Orchomene nanus than control (unbaited) traps. Traps were not inherently attractive. Crab bait was significantly more attractive than fish, or scampi. However, in a comparison between crushed representatives of three crab genera, no significant differences in the ability to attract Orchomene nanus were detected. Live Carcinus maenas attracted no Orchomene nanus. Crab limbs were as attractive as crab bodies minus limbs. Freshly dead crabs were more attractive than dead crabs that had been leached for 6 days. Fifty percent of Orchomene nanus survived 27 days in situ without extraneous food (although cannibalistic possibilities cannot be ruled out); a facility that would help overcome interludes of food shortage. All size-categories of Orchomene nanus were attracted to crab bait. Orchomene nanus is thus an unusual species: a diminutive, selective (and possibly obligate) scavenger specializing on high quality carrion.