Feeding and Substrate Preference in Five Species of Phoxocephalid Amphipods from Central California

Abstract

Feeding habits and sediment preferences were examined for 5 spp. [Granditoxus grandis, Mandibulophoxus gilesi, Foxiphalus obtusidens, Rhepoxynius abronius, R. fatigans] of phoxocephalid amphipod crustaceans from high-energy sandflats in California. Crop contents indicated that phoxocephalids are predaceous omnivores, consuming a variety of meiofaunal prey as well as detritus. Prey availability, prey size and predator size were related to the meiofauna consumed. In laboratory preference experiments, different species of phoxocephalids showed different preferences for sediment size. Amphipods swam from sediment that was much finer or coarser than the sediment they normally inhabited in the field. They burrowed rather than swam from sediment that was only slightly coarser or finer than their native sediment. Each species had the greatest preference in the laboratory for sediments that were collected where the largest populations were found. Habitat selection could allow phoxocephalids to locate favorable microhabitats and help to maintain broad depth zonation.