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Endocrine control as a determinant of larval quality in fish aquaculture


Many aspects of development, differentiation and metabolism in vertebrates are regulated by small biologically active molecules such as thyroid hormones and retinoids. They act via a family of intracellular receptor proteins which act directly on target genes. Thyroid hormones are passed on to the eggs by broodfish prior to spawning (Kobuke et al., 1987; Tagawa and Hirano, 1987; Brown et al., 1987; Greenblatt et al., 1989, Tagawa ef al., 1990) and may provide the necessary physiological regulation for growth, development and osmoregulation in larvae prior to the functional development of their own endocrine glands. There is little doubt that thyroid hormones are essential for fish development, for example, in the metamorphosis of the flounder (Miwa et al. 1988; Yamano ef al. 1994). Also, treatment of larvae from several species with thyroid hormone has beneficial effects on development and survival (Brown and Nunez, 1994) and it has recently been shown that thyroid hormone receptors are abundant in sea bream larvae (Llewellyn et al., 1996). However, the investigations into thyroid hormones so far have centred on hormonal measurements or treatments and have not attempted to identify the tissues, which respond to these hormones during development by detecting the presence of specific receptors in those tissues. Growth hormone (GH) is one of the major hormones regulating growth in vertebrates. However, despite evidence that GH cells are present (Power and Canario, 1992; Cambre et al., 1990) and GH is synthesised in recently hatched fish (Funkenstein et al., 1992) and that, in the Japanese flounder, GH expression increases throughout metamorphosis, the functional importance of GH in fish larval development remains to be ascertained.
The prime aim of the project is to establish the importance of thyroid hormones and growth hormone (GH) in the normal and abnormal development of two marine species. These are the Atlantic halibut (Hippoglossus hippoglossus) a cold-water fish with considerable potential as a new aquaculture species and the sea bream (Sparus aurata), a warm-water fish cultivated in the Mediterranean and Portugal, but for which problems of larval culture elevate production costs and reduce its economic potential.

This will be investigated by:
- The determination of whole body T4, T3 growth hormone (GH) and IGF1 profiles during development of the larvae and young fish.
- The determination of the stages at which tissues become responsive to thyroid hormones through the production of thyroid hormone receptor (THR) and GH by the production of IGF1.
- The experimental manipulation of the levels of GH, thyroid hormones, and THRs and the determination of the effect of this on development.
- The generation of a model system for abnormal development, based on the actions of retinoic acid, a regulator of vertebrate development already implicated in the production of abnormal larvae in vertebrates. The use of this model system to determine morphological and molecular aspects of abnormal development.


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Funding Scheme

CSC - Cost-sharing contracts


University of Wales Cardiff

CF1 3TL Cardiff
United Kingdom

Participants (3)

Fiskeldi Eyjafjardar Ltd.
Glerargotu 34
602 Akureyri
Campus De Gambelas
8000 Faro
University of Goeteborg
Medicinaregatan 18
40530 Goeteborg