Arm regeneration in two populations of Acrocnida brachiata (Montagu) (Echinodermata: Ophiuroidea) in Douarnenez Bay, (Brittany: France): An ecological significance

Abstract

The incidence of arm regeneration in the brittlestar Acrocnida brachiata is assessed for an intertidal and a subtidal population in the Bay of Douarnenez, France. The growth rate of regenerating arm parts in the field and under laboratory conditions and the annual regenerating biomass production complete the study. The frequency of arm regeneration is extensive and comprises nearly 70% of the total arm population in both sampling sites. The position of the breakage points mostly occur in mid-arm level in the tidal flat area and mainly in the distal third part of the arms in the subtidal site. The biomass composed of regenerating tissue is significantly different in both zones accounting for 11.1% (±9.5%) of the total individual biomass in the intertidal area and 6.4% (±8.4%) subtidally. Actively feeding arms appear to be the least damaged. To maximize fitness, the intertidal individuals of Acrocnida brachiata seem to allocate energy to arm regeneration at the expense of somatic growth. Highest arm growth per individual was recorded in the field and comprises 1.2 mm·day −1 for individuals with two amputated arms. Subtidally, the annual production invested in regenerating tissue is 33 g dry wt·m −2 (19 g AFDW·m −2).