Insights into first feeding of newly-hatched paralarvae of the merobenthic octopus, Octopus tetricus

Abstract

The commercial aquaculture of merobenthic octopus species is constrained by the inability to raise large numbers of paralarvae through their planktonic phase from hatching to juvenile. Knowledge on the early feeding behaviour and nutrition requirements of octopus paralarvae is critical for addressing this challenge. This study evaluates the food seizure behaviour of Octopus tetricus paralarvae at age 0–5 dph (days post-hatch) under different experimental conditions including, egg incubation method, tank colour, and live prey versus formulated food pellets. The percentage of paralarvae that attacked food items and the percentage of paralarvae that had at least one successful seizure at the age 0–5 dph were measured in relation to the experimental conditions. The number of attacks and successful seizures of food items by paralarvae was not affected by the egg incubation method, i.e., maternal grooming versus artificial incubator tank. A higher percentage of paralarvae performed attacks in black tanks (70 ± 8%) compared to grey tanks (44 ± 6%) with no differences to white tanks (58 ± 7%) when Artemia nauplii were supplied. However, no differences in the proportion of paralarvae with successful seizures were found among the three tested tank colours. A higher percentage of paralarvae attacked formulated food pellets (69 ± 6%) compared to Artemia nauplii (44 ± 6%) in grey tanks. An overall trend was observed of O. tetricus paralarvae having lower successful seizures at 0 dph that increased until 2 to 3 dph followed by a steep and continuously decline in success through until 5 dph. On average 31 ± 3% of paralarvae had at least one successful seizure of formulated food pellets in the first 5 min after the pellets were supplied compared to 4 ± 1% in the subsequent 10 min. In contrast, feeding on Artemia nauplii remained steady over the full 15 min experimental period. The results indicate that the effect of tank colour on feeding behaviour warrants further investigation as it affects the ability of the paralarvae to detect and attack potential food items. Moreover, the results demonstrate that artificial egg incubation did not have a negative effect on the feeding behaviour of paralarvae, and that formulated food pellets have the potential to be developed as an alternative to live prey for the culture of paralarvae of this species.