Meeting Abstract
Sea urchins (Echinoidea) from shallow, well-lit environments are commonly observed lifting materials from the surrounding substrate onto their aboral surfaces. This covering behavior may provide a variety of benefits, including protection from ultraviolet radiation and predator avoidance. However, covering behavior in deep-water sea urchins is rarely observed, and its functional significance remains speculative. Using SeaSled, a towed-camera vehicle, we conducted photo-transects off Anvers Island and in Marguerite Bay along the western Antarctic Peninsula (390–2100 m depth). We recorded the number of sea urchins, incidence of covering behavior, types and availability of covering materials, potential predators of sea urchins, and potential prey items for predators. The regular sea urchin Sterechinus spp. was observed at all depths, and the percentage of individuals exhibiting covering behavior increased with depth. There was a significant positive correlation between the incidence of covering behavior and the density of king crabs (Anomura: Lithodidae), crushing predators that may be extending their range up the Antarctic continental slope as a result of warming ocean temperatures. In contrast, covering behavior was not positively correlated with the availability of covering materials, the densities of non-crab predators, the total density of predators, or the availability of prey. Our results suggest that covering in deep-water sea urchins is a behavioral response to reduce predation by king crabs.
