Investigating lighting intensity and angle to facilitate feeding in paralarvae of the common Sydney octopus, Octopus tetricus

Abstract

Efforts to establish sustainable octopus aquaculture are hindered by high mortality of octopus paralarvae during larviculture. The optimum culture conditions in which paralarvae can best visualize and capture food items for nutrient delivery remains undescribed. This study investigated the ingestion of prey by Octopus tetricus paralarvae, aged 2 days post hatch, under different combinations of light intensity (600 lx or 15 lx) and light angle (0°, 45°, or 90°). Groups of ten octopus paralarvae were allowed to feed on 3000 Artemia under one of the six lighting combinations for 6 h, whereafter intact or partially ingested Artemia were counted. The greatest total number of Artemia ingested for all paralarvae in a lighting treatment was 279 Artemia under a high intensity light sourced from 90° (P < 0.001). This total number was 77 % greater than the second most successful light treatment, low intensity light sourced from 90° (P < 0.001) and 675 % greater than the least successful light treatment, low intensity light sourced from 45° (P < 0.001). Prey ingestion by individual paralarva was six times greater under high intensity light sourced from 90° than under low intensity light sourced from 45°. Examination of Artemia remains suggested paralarvae captured Artemia in regions of high body surface area, providing information for improved nutrient delivery. Under the best lighting, paralarvae would have fully ingested more Artemia suggesting that feeding efficiency is highly dependent on improved prey visibility. Future rearing efforts should consider these essential factors of light to optimise feeding success with octopus paralarvae.