Ageing and growth of the Arctic brittle star Ophiopleura borealis (Echinodermata: Ophiuroidea) from the Barents Sea and North East Greenland

Abstract

Species inhabiting cold-water environments exhibit typically slower growth and a longer lifespan than warm-water species, implying a slowed ability to recover from natural and anthropogenic disturbances. Longevity estimates for species inhabiting the Arctic region are sparse, despite the ongoing changes and disturbances in the region. Brittle stars (Ophiuroidea) often dominate Arctic shelf epibenthic communities, impacting biogeochemical fluxes and sediment structure. Assessing their resilience to disturbances relies on estimates of their longevity. However, only a handful of studies on brittle star age are available, including three on Arctic species. In this study, I showed that growth bands similar to those seen in the arm bones of other brittle star species were also present in O. borealis specimens from North East Greenland and the Barents Sea. By counting the growth bands using scanning electron microscopy (SEM) and correcting the count for overgrown bands, ages could be estimated in 80 individuals as growth bands are likely formed annually. The maximum age estimated was 39 years, which is the first longevity estimate to be presented for O. borealis. The Specialized von Bertalanffy, the Gompertz and the Single Logistic growth functions were applied to the age data to construct growth curves. The growth constants estimated by each model indicated the growth of O. borealis to be similar to that of other polar brittle stars. These results contribute to information on the longevity of an Arctic benthic invertebrate – which can be applied when estimating impacts of disturbances on the species and, consequently, the Arctic benthic ecosystem.