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ARRESTED DEVELOPMENT: The molecular and Endocrine Basis of Flatfish


Flatfish species form a major focus of the diversification of European marine aquaculture industry. However, production has been severely hampered by biological problems in larval rearing. This project focuses on solving the major problem of arrested metamorphosis, in order to reliably control the resulting juvenile quality and production quantity. This will be achieved by addressing key questions regarding the morphological, endocrine and molecular basis of metamorphosis in the Atlantic halibut as a model species. The ultimate goal of the project is therefore to strengthen European aquaculture of marine flatfish species, an important emerging industry in many rural areas, by facilitating the production of fully functional juveniles.

The high incidence of metamorphic abnormalities represents a serious impediment to the successful aquaculture of marine flatfish by limiting the cost-effectiveness of the juvenile production industry. The objectives of this project are to determine the biological bases for abnormalities arising during metamorphosis of a model cultured marine flatfish, the Atlantic halibut. This will be achieved by comparing normally and abnormally metamorphosing larvae in terms of differential gene expression, endocrine regulation, and biochemical and morphological transformations. This will help establish improved, cost-effective rearing techniques for the production of marine flatfish juveniles, ultimately strengthening European aquaculture of marine flatfish species, an important emerging industry in many rural, coastal areas.

Description of the work
1) The events of metamorphosis in halibut will be analysed by monitoring biochemical and morphological markers of metamorphosis. These markers are skeletal development, erythrocyte morphology, expression of troponin-T isoforms, production of gut enzymes, and expression of immunoglobulins.
2) Differential gene expression will be analysed by screening of a gene microarray based on genes induced during metamorphosis, This will allow high throughput analysis of an extensive panel of genes involved in metamorphosis.
3) Endocrine regulation of metamorphosis will be analysed in terms of hormone levels and hormone responsiveness . Tissue and plasma levels of thyroid hormones, cortisol, growth hormone and IGF-1 during metamorphosis will be determined by RIA. Prolactin expression will be monitored by assaying its mRNA. The genes encoding receptors for prolactin, cortisol and growth hormone will be cloned. The temporal and spatial expression of these genes, along with the already-cloned thyroid hormone receptor will be analysed during metamorphosis by competitive RT-PCR and in situ hybridisation The role of individual hormones during metamorphosis will be further investigated through hormone treatment experiments on pre-metamorphic and metamorphosing larvae.
4) Abnormally metamorphosing larvae. will be collected, grouped according to type of abnormality (arrest of metamorphosis, pigmentation defect, inappropriate eye migration etc). These larvae will be compared with normally metamorphosing larvae from the same culture in terms of expression of biochemical and morphological markers of metamorphosis, differential gene expression, expression of hormone receptors and hormone content. This will indicate the underlying molecular and/or endocrine bases of the various abnormalities.
5) In vivo treatments with hormones and nutritional supplements will be carried out to establish functional relationships.

A staging scheme for metamorphosis, based on biochemical, morphological endocrine and genetic markers. A ""metamorphic"" microarray of 700 genes to identify endocrine and molecular basis of metamorphic arrest. Larval treatments with hormones, iodine arid selenium to establish functional relationships between nutritional factors, endocrine axes and metamorphosis, establishing ""functional feeds"" and scientific tools for effective metamorphic larval aquaculture.

Funding Scheme

CSC - Cost-sharing contracts


University of Göteborg
405 30 Göteborg

Participants (4)

Glerargata 34
Universidade do Algarve
Campus De Gambelas, Estrada De Penha
8000-100 Faro
University of Bergen
Prof. Keysergt. 8
5020 Bergen
University of Wales, Cardiff
United Kingdom
55 Park Place
CF1 3TE Cardiff