Defining Octopus vulgaris populations: A comparative study of the morphology and chromatophore pattern of paralarvae from Northeastern and Southwestern Atlantic

The chromatophore pattern of cephalopods provides a rapid and relatively easy means to identify species. Therefore, this paper describes and compares the morphology and chromatophore pattern of Octopus vulgaris paralarvae from different geographic regions, specifically, the notheastern (Galicia, Spain) and the southwestern (Southern Brazil), Atlantic, and ultimately, contributes to knowledge for future discrimination of populations of O. vulgaris from both regions. The eggs and paralarvae of both localities were incubated in the laboratory and reared at 21 and 22 °C from hatching to 17 or 45 days of age. Important differences were observed on the chromatophores pattern of paralarvae from both regions. In the ventral mantle, between 23 and 36 chromatophores were found in the Brazilian paralarvae, whereas between 16 and 20 were found in the Spanish paralarvae. However, Brazilian paralarvae showed considerably less extrategumental chromatophores over the viscera (6–9) in the dorsal mantle than the Spanish paralarvae (6–20). Differences were also detected in the funnel, 4–6 chromatophores (four different patterns) versus 4 (single pattern), respectively. These results showed substantial differences between the chromatophore patterns of paralarvae from both regions, which could provide evidence for the existence of distinct populations or even cryptic O. vulgaris-like species along the Southern Brazilian coast.