Embryonic development, description and cultivation of common octopus (Octopus vulgaris) on the south coast of Brazil

Author: Lisiane Barcelos da Silva (Currículo Lattes)
Supervisor: Dra Érica Vidal

Abstract

There is a great lack of information about the physical and behavioral needs of the parasites, as well as their food preferences, which makes it difficult to maintain them in the laboratory. Studies that contribute to verify the factors that affect the survival of the parasites during the larviculture and for a greater knowledge of the initial stages of development, biology and ecology of the parasites of the common octopus of the south coast of Brazil, are necessary for the development of experimental protocols for cultivation. To assess the early stages of development of the common octopus, estimates of the calf absorption rate, wet and dry weight, organic and inorganic weight, were obtained from eggs incubated at 24 ± 1°C, every 48 hours during embryonic development. . After hatching, the flares were separated into two groups,starvation at 19°C and starvation at 24°C, to assess the importance of calf content in their survival potential during larviculture. The results indicate that the embryo biomass loss was relatively low, as there was a reduction of only 12% in the organic weight of the eggs, suggesting that the calf was efficiently converted into body mass at the chosen incubation temperature. The calf reserve represented 20 to 32% of the wet body weight of the parasites at hatching, allowing them to survive up to 8 days at 19°C and up to 10 days at 24°C when in starvation. However, survival rates above 70% were recorded on Day 5 for parasites maintained at 19°C and on Day 3 at 24°C. These results indicate that higher mortality rates were previously recorded for parasites maintained at 24°C,due to higher metabolic rates, resulting in faster calf absorption. There is evidence that the common octopus is a member of a complex of cryptic species. Thus, the morphological description of paralarvas from the south coast of Brazil and comparison of the chromatophore pattern between paralarvas from the south coast of Brazil and the northwestern Atlantic (Vigo, Spain) were performed. The eggs and flails from both locations were incubated and maintained at temperatures of 20°C ± 2°C. Important differences were observed between the chromatophores pattern of the paralarvas of both localities, mainly in the ventral region of the mantle and the head. However, to assess the degree to which these differences may be involved in the complexity of the species' taxonomic position, molecular genetic support would still be necessary.One factor that has contributed to the increase in mortality rates of the parasites is related to the inadequate physical conditions of the cultivation systems, with injuries being observed in the arms of the parasites kept in 96 L circular tanks. In order to reduce these injuries 3 internal configurations of culture tanks and hydrodynamics were tested. Histological analyzes of normal and injured paralarva arms were performed to characterize and identify the cause of these injuries. Paralarvas kept in tanks with circular current and aged 20, 24 and 30 days (d) showed loss of suction cups and decreased or absent OK. The cobs aged 15 d kept in tanks with upward current showed a nodular structure that indicated the beginning of the abrasive process. Paralarvae of 24 d kept in tanks with vertical converging currents did not present epithelial damage, representing the best hydrodynamics tested. The results indicate that the injuries are physical, and that they can be reduced by remodeling the internal configuration of the tanks and hydrodynamics. Therefore, this shows that hydrodynamics is one of the causes of mortality of the parasites during cultivation, which had not been observed before. Thus, the contact of the brackets with the walls should be avoided whenever possible.

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