Desarrollo histológico y ontogénico del aparato digestivo de "Octopus vulgaris" cuvier, 1797 (Mollusca: cephalopoda)

Resumo

Abstract Octopus vulgaris is a species with high fish production that presents both artisanal and industrial fisheries. The annual world catch for this species seems to have a decline from 100 thousand tonnes caught in the 1970s to 34 thousand tonnes caught in 2015. The high sales price that reaches this species, as well as high demand, makes this an interesting species to develop its aquaculture. Today the commercial aquaculture of this species is not developed and it is limited by various factors such as: poor physiological and biological knowledge of the paralarvae, their nutritional requirements, and standardisation of cultivation techniques during the paralarvae period. The two bottlenecks to obtain the commercial aquaculture of this species are high mortalities during the planktonic or paralarva period and the absence of adequate diets. The mainly research efforts are focus on obtaining diets suitable for all stages of the life cycle. Despite a large number of studies on the aquaculture of paralarvae, few have focused on the standardisation of culture techniques, in increasing the physiological or biological knowledge of this species the first days of life or develop tools to know the nutritional status of the paralarvae. The main objectives of this study were to know the ontogeny of the digestive system of Octopus vulgaris from the earliest stages of embryonic development to the first month of life. Also, a new technique has been studied to know the nutritional status of the paralarvae in culture based on the visual changes of the digestive gland. In order to study the ontogeny of the digestive system, the anatomical development study was carried out by means of the implementation of a 3D modelling methodology and the histological study of the most important organs and structures have been done using conventional, trichrome and histochemical stains. This allowed us to recognize the histological structures of the organs and their secretions at different ages. The visual study of the digestive gland colour variations in paralarvae during the rearing was realized by means of the photographed and measurement of the variations of the different colour areas in this gland. The results of this study allowed us to differentiate three phases of the development of the digestive system during the organogenic period in the embryos, based on the structures and organs in development and their histological differentiation. After hatching all the structures and organs of the digestive system are present, although it is underdeveloped histologically Based on the alimentation, growth and histological and functional characteristics of the digestive system we have differentiated 2 stages of development, early post-hatch phase and later post-hatch phase, in the paralarva stage until the first month of life. The study of visual variations of the digestive gland has proven to be a viable technique for the study of the nutritional status of the paralarvae the first days of life. This tool allows us to differentiate the percentage of paralarvae that are being fed into the crop, which represents an advance in the aquaculture of the paralarvae.