Trophic ecology of Octopus vulgaris paralarvae along the Iberian Canary current eastern boundary upwelling system

Abstract

Abstract Our knowledge of the diet of wild Octopus vulgaris is restricted to the first two weeks of its planktonic phase when they are selective hunters found in the coastal area. These small paralarvae, bearing only three suckers per arm, are transported by oceanic currents from the coast towards offshore waters where they complete the planktonic phase in two months. Herein, we have investigated the trophic ecology of O. vulgaris paralarvae as they drift from the coast into the ocean of the Iberian Canary Current (ICC) eastern boundary upwelling system, to evaluate if their specialist trophic behaviour is held throughout the planktonic phase. Paralarvae (n = 100) were collected in Northwest Spain (n = 5, three suckers per arm), across the Northwest Iberian Peninsula (n = 60, three to five suckers per arm) and off the west coast of Morocco (n = 35, three to 15 suckers per arm). Using high-throughput amplicon sequencing up to 90 different prey was identified in 95 paralarvae. Diet varied along the ICC, with the most discriminant groups being crab larvae and siphonophores in the northern part of the ICC and crab larvae and cnidarians in the south. Ontogenetic changes in the diet were detected between coastal and oceanic communities, evidenced by the decreasing contribution of coastal meroplankton and an increase in holoplankton, including siphonophores, pteropods and krill. Averaged trophic niche breadth values ranged from 0.16 to 0.31, thus suggesting that O. vulgaris paralarvae are specialist predators throughout their planktonic phase, a finding that has important implications for the aquaculture of this species.