SWIMMING BEHAVIOR AND FOOD SEARCHING IN PLANKTONIC OCTOPUS-VULGARIS CUVIER FROM HATCHING TO SETTLEMENT

The planktonic life in Mediterranean Octopus vulgaris lasts about 2 mo nths but we know virtually nothing of this phase of its life history, which represents around 10-15% of the estimated life span. Swimming be haviour from hatching to settlement was studied by video-recording tec hniques, using five groups aged 1, 15, 30, 42 and 60 days, by when the y have become benthic. During the planktonic stage, the backwards, squ id-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 depu rator (L.) and Pagurus prideaux Leach; it is that of a visual predator . The forward displacement typically forms part of this predatory beha viour. During the planktonic phase, the presence of prey increases the turning rate and reduces the swimming speed of Octopus vulgaris indiv iduals. Both responses may improve the exploitation of patchy food env ironments.