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  • 1
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The effect of egg vitamin A (VA) status and egg incubation temperature on the development of spinal disorders was investigated in Atlantic salmon Salmo salar fry. Atlantic salmon eggs were sorted into two groups with high VA (3·3 ± 0·1 μg retinol g−1 dry mass) and low VA (2·2 ± 0·3 μg retinol g−1 dry mass) status before fertilization and incubated at high (14° C) or low (8° C) temperature from 133 day degrees until the onset of feeding. High egg incubation temperatures increased the concentration of retinol in the eggs: the high VA and high temperature group displayed a significantly higher retinol concentration than the high VA and low temperature group (P = 0·001). After hatching, all experimental groups increased their retinol concentration. The source of the increased retinol levels was probably retinal, although astaxanthin may also be a VA precursor after hatching. Atlantic salmon fry incubated at high temperatures had increased amounts of notochord tissue. When measuring morphogenic activity in the notochord using the expression of sonic hedgehog (shh, mRNA), however, no significant difference was found between the experimental groups. No clear effect of VA status or incubation temperature could be found on the formation of the early vertebral column although Atlantic salmon fry incubated at low temperatures had less regular constrictions of the prospective vertebral column than fry incubated at high temperatures.
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 2016-09-14
    Description: Food uptake follows rules defined by feeding behaviour that determines the kind and quantity of food ingested by fish larvae as well as how live prey and food particles are detected, captured and ingested. Feeding success depends on the progressive development of anatomical characteristics and physiological functions and on the availability of suitable food items throughout larval development. The fish larval stages present eco-morpho-physiological features very different from adults and differ from one species to another. The organoleptic properties, dimensions, detectability, movements characteristics and buoyancy of food items are all crucial features that should be considered, but is often ignored, in feeding regimes. Ontogenetic changes in digestive function lead to limitations in the ability to process certain feedstuffs. There is still a lack of knowledge about the digestion and absorption of various nutrients and about the ontogeny of basic physiological mechanisms in fish larvae, including how they are affected by genetic, dietary and environmental factors. The neural and hormonal regulation of the digestive process and of appetite is critical for optimizing digestion. These processes are still poorly described in fish larvae and attempts to develop optimal feeding regimes are often still on a ‘trial and error’ basis. A holistic understanding of feeding ecology and digestive functions is important for designing diets for fish larvae and the adaptation of rearing conditions to meet requirements for the best presentation of prey and microdiets, and their optimal ingestion, digestion and absorption. More research that targets gaps in our knowledge should advance larval rearing.
    Type: Article , PeerReviewed
    Format: text
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