Population structure, habitat preferences, feeding strategies, and diet of the brittle star Ophiopholis aculeata in nearshore and offshore habitats of the northwest Atlantic

Abstract

Ophiopholis aculeata is a ubiquitous brittle star (Echinodermata: Ophiuroidea) known to occur from the upper subtidal to the bathyal zone. Individuals from shallow inshore habitats (rhodolith beds and rock fields) and deeper offshore locations in eastern Canada were studied to assess the population structure, habitat selection, diet, and feeding strategies of this species through use of stable isotope analyses, gut contents, and laboratory experiments. Potential drivers of habitat selection such as depth, light conditions, body size, sex, intraspecific competition, and presence of predators were examined. This study highlighted variable population size structures and abundances as well as diversified food sources and feeding strategies (i.e., suspension and deposit feeding, scavenging, predation on live organisms, and even cannibalism) as a function of native depth and habitat. It also revealed that studies on the feeding biology of brittle stars must carefully consider sex and life stage as driving factors.