Browsing by Author "Reis, Diana Filipa Botelho"
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- Fatty acid and lipid class metabolism of common octopus (Octopus vulgaris) and of European cuttlefish (Sepia officinalis) at early life stagesPublication . Reis, Diana Filipa Botelho; Andrade, José Pedro; Sykes, António V.; Rodriguez, CovadongaOctopus vulgaris and Sepia officinalis are two species of cephalopods that have been recognised with a great potential for aquaculture.
- Improvement of common octopus (Octopus vulgaris) paralarval culture, based on studies of feeding and nutrition with alternative preysPublication . Reis, Diana Filipa Botelho; Andrade, José Pedro de Andrade e Silva; Sykes, António de Vilhena Andrade Ferreira; Berro, Eduardo Almansa; González, Covadonga RodríguezAt the moment, the biggest bottleneck in Octopus vulgaris culture is the paralarvae stage, which is characterized by high mortalities and poor growth. This thesis pretended to study the effect of three different preys (Palaemon elegans, Grapsus grapsus and Artemia spp. enriched with Tetraselmis chuii) on the survival and growth of 0. vulgaris paralarvae. It also targets the nutritional composition of newly hatched paralarvae and the effect of the diets after nine days of culture. Prey biological characteristics and level of predation were also covered during this study. Regarding growth, survival and the biochemical composition of paralarvae, two experiments were conducted. In the 1” experiment, paralarvae were reared at density of 5 paralarvae/L and Artemia spp. juveniles (1-ART) and P. elegans zoea (1-PAL) were tested. In the 2“d experiment, the paralarvae rearing density was reduced to 1.5 paralarvae/L to raise the number of preys per paralarvae and Artemia spp. juveniles (2- ART), P. elegans zoea (2-PAL) and G. grapsus zoea (2-GRA) were tested. Low survival rates were obtain during the 1” experiment and although higher rates were obtain during the 2“d experiment, no statistical differences (P>0.05) between experiments and treatments were found due to the high variability recorded. Nonetheless, higher growth rates (P<0.05) were found in treatments with low paralarvae density (2“d experiment) and fed with decapod crustacean zoeae (2-PAL - IGR=5.18i 0.96% and 2-GRA - IGR=6.29 Í 1.10). The biochemical composition of octopus hatchlings in the present study was similar to that reported in previous works. After nine days of rearing it was observed a nutritional change in paralarvae composition. Regardless from prey provided, a reduction in DHA and PUFA content and DHA/EPA ratio was detected (P<0.05). Nevertheless, the best rearing success was obtained in the 2-PAL and 2-GRA groups, which were the ones with the higher DHA/EPA ratio (P<0.05). Although no differences were found between the 2-ART group and octopus hatchlings (P>0.05), the remaining treatments displayed a raise in ARA content that might be related with food input. The artemia juveniles (prey with the poorer results in terms of paralarvae rearing) were the most different prey contrasting with the FA profile of octopus paralarvae, suggesting the importance of this factor in the octopus development. On the other hand, crab zoeae, which presented good rearing results, also presented low content in protein, phospholipids and to some extent cholesterol; which were higher in artemia juveniles (P<0.05). The prawn zoea was the most attacked and captured prey during the predation trial and, although not different from artemia juveniles due to the high variability (P>0.05), both decapod crustacean zoeae were highly ingested by the octopus paralarvae. The low number of attacks and captures on crab zoeae observed and the high number of ingestions recorded could have been related to the fact that, when placed in the tank, most of the zoeae sank rapidly to the bottom, not being quickly detected. From the present results it seems that not just the biochemical composition of prey influences the octopus; paralarvae development, but also the number of preys ingested may suggest as a limiting factor. A reduction in the water column depth of the rearing tanks could reduce the energy spent in prey capture from the bottom, improving energy efficiency and promoting paralarvae growth. Considering the results obtained with Artemia spp. despite being the most available and easiest prey to culture, it does not seem to be an adequate prey for octopus paralarvae. On the other hand, decapod crustacean zoea seems a promising model if zoeae availability is improved.