Post-graduate theses
Current Record: 628 of 800
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| Identifier |
uch.biology.msc//2003szisch |
| Title |
Οντογένεση των θυροειδικών ορμονών στην τσιπούρα (Sparus aurata) |
| Creator |
Szisch, Vera
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| Abstract |
The thyroid gland in fish produces and secretes two thyroid hormones (THs), namely triiodothyronine (T3) and thyroxine (T4), which regulate a wide range of developmental, metabolic and homeostatic processes, such as metabolism, development, reproduction, metamorphosis and behavior. In fish, the transformation of larvae into juveniles is frequently termed metamorphosis. Metamorphosis arises from a series of regulated processes that involve tissue differentiation, biochemical, molecular and physiological changes. The most dramatic manifestation of this is the classic metamorphosis of flatfish (Pleuronectiformes) in which bilaterally symmetric pelagic larvae transform into asymmetric benthic juveniles with both eyes on the same pigmented side of the body. The role of THs in metamorphosis of flatfish today is well understood, but relatively little attention has been given to the role of THs in the change from larvae to juvenile in other species, which have a less dramatic transition than the flatfish. The aim of the study was (1) the development of a suitable method for the determination of the thyroid hormone content in eggs and larvae of the gilthead sea bream (Sparus aurata) and (2) the investigation of the ontogeny of the thyroid hormones in the early developmental stages of the sea bream. In the present study, the ontogeny of the thyroid hormones was related to specific morphological characteristics during early development of the sea bream. Thus, the present study extends those that have been performed in the past in other teleostean species. The sea bream was chosen as the study organism since it is considered a model organism and is a species of high economic value especially in the Mediterranean region. With this study, it is shown for the first time that substantial amounts of thyroid hormones are present in the eggs and the larvae of the sea bream. The amount of T3 in the eggs was found to be higher than that of T4, which supports the general hypothesis, that in the eggs of marine species the level of T3 is often higher than that of T4. The concentration of T4 decreased until hatching, while the level of T3 reached the minimum at the time of the first feeding. As development progressed, both hormone levels increased until metamorphosis was completed. This result leads to the conclusion that the metamorphosis in sea bream is dependent on the action of thyroid hormones. The development of a suitable method for the determination of the thyroid hormone content in early developmental stages of the sea bream allows the investigation of the ontogeny of the thyroid hormones also in other species, which are closely related to the gilthead sea bream.
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| Issue date |
2003-11-01 |
| Date available |
2003-11-05 |
| Collection
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School/Department--School of Sciences and Engineering--Department of Biology--Post-graduate theses
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Type of Work--Post-graduate theses
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| Permanent Link |
https://elocus.lib.uoc.gr//dlib/d/e/3/metadata-dlib-2003szisch.tkl
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| Views |
285 |
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