Predation and regeneration of Ophiura sarsi on the US continental slope: Use of a manned submersible to perform in situ experiments

Using a manned submersible, we have studied a patch of Ophiura sarsi (>30.m⁻²) at 500m depth in which over 98% of the individuals and over 90% of the arms exhibit regeneration scars. Growth rings in the vertebral ossicles of the arms are invariably fewer on the distal sides of scars; if annual, these rings indicate arm loss rates on the scale of years. Tethering and caging experiments also indicated that predation rates are low and regeneration rates are slow (years). Size-frequency analyses indicate that this population is a single cohort, but vertebral ossicle growth rings ranging from 5–25 in similarly-sized animals suggest a mixed-age group. Ongoing studies include calcein marking for age validation, assessment of potential predators, and sources of nutrition.