Swimming behaviour and food searching in planktonic Octopus vulgaris Cuvier from hatching to settlement

The planktonic life in Mediterranean Octopus vulgaris lasts about 2 months but we know virtually nothing of this phase of its life history, which represents around 10-15% of the estimated life span. Swimming behaviour from hatching to settlement was studied by video-recording techniques, using five groups aged 1, 15, 30, 42 and 60 days, by when they have become benthic. During the planktonic stage, the backwards, squid-like jet swimming was the predominant type of displacement. Strong morphometric changes, basically in arm growth, influence their jetting capacities and probably the settlement process. Feeding behaviour was analyzed using two species of decapod zoeae as prey, Liocarcinus depurator (L.) and Pagurus prideaux Leach; it is that of a visual predator. The forward displacement typically forms part of this predatory behaviour. During the planktonic phase, the presence of prey increases the turning rate and reduces the swimming speed of Octopus vulgaris individuals. Both responses may improve the exploitation of patchy food environments.