Sibling cannibalism on the small octopus Robsonella fontaniana (d'Orbigny, 1834) paralarvae

Several experiments were conducted to determine if cannibalism or other aggressive behaviour occurs during the planktonic stage of the small octopus Robsonella fontaniana. Paralarvae from the same egg mass were treated under different rearing densities, with and without the presence of food, different water volume and confronted with the development of a feeding habit. Observation of aggressive and cannibalistic behaviour among sibling paralarvae was present in the majority of groups and treatments. However, in the largest water volume with the lowest density maintained (2 paralarvas/500 ml) no sign of aggressive behaviour was observed with or without the presence of food. The degree of cannibalism observed during this study fluctuated within 12.5-65.5%, with attacks starting between the 7th and 10th day, and where the time at which experiments finished (last single individual within recipient) was observed 8 days after attacks began. Paralarvae put under a feeding regime of 5 days did not show differences in all measured parameters between those that were continuously fed and the ones which were deprived of food.