Evaluation of sediment particle size selection during feeding by the holothurian Parastichopus regalis (Cuvier, 1817)

Abstract Parastichopus regalis is an epibenthic holothurian common in the Mediterranean Sea and the NE Atlantic, which feeds on the upper layer of the sediment playing a significant role on soft-bottom dynamics. Whether or not P. regalis is able to select the sediment ingested by size is the question of this study. For this purpose, a comparison between grain size distributions of the seabed sediments and the digestive contents of sea cucumbers were carried out. We performed the comparisons among sediment distributions through the median diameter D 50 and the granulometric dispersion D 84 ∕ D 16 . The results showed that the size of the sediment within the holothurians was significantly smaller and more uniform than the ones in the seabed. Evidence showed that P. regalis select sediment by particle size during feeding, choosing the smaller particles. This finding reports novel information on the feeding behavior of this species, a fishery resource of local interest and importance in the Western Mediterranean region.