Mitchell Fleming will defense of his PhD Thesis entitled:
« Environmental and neuroendocrine control of smoltification in long-river (Loire-Allier) Atlantic salmon, Salmon salar »
Thursday, December 20th at 14h00
At the Amphithéatre de la Galerie de Paléontologie, Jardin des Plantes, Muséum National d'Histoire Naturelle, Paris
Jury members:
- Mme. Catherine Pasqualini (rapporteur), CR CNRS, Gif-sur-Yvette, France
- M. Ian Mayer (rapporteur), PR NMBU, Oslo, Norway
- M. Gilles Boeuf (examinateur), PR SU, Paris, France
- M. Laurent Sachs (examinateur), DR CNRS, Paris, France
- M. Patrick Martin (examinateur), Dir CNSS, Chanteuges, France
- Mme. Karine Rousseau (co-directrice de thèse), MC MNHN, Paris, France
- Mme. Sylvie Dufour (directrice de thèse), DR CNRS, Paris, France
Abstract: Environmental and Neuroendocrine control of smoltification in long-river (Loire-Allier) Atlantic salmon, Salmo salar
Smoltification is a metamorphic event in salmon, which initiates downstream migration and pre-adapts juvenile for seawater entry. The PhD aimed at investigating endocrine and environmental regulation of smoltification in the endangered long-river Loire-Allier Atlantic salmon. We report the presence and functional divergence of thyrotropin ß-subunit paralogs (tshßa& tshßb) in Atlantic salmon and showed a peak pituitary expression of tshßb at smoltification which was concomitant with the initiation of downstream migration. This is the first time pituitary TSH expression is related to smoltification and downstream migratory behavior. Experimental exposure to constant short-day photoperiod or to increased temperature did not markedly affect the peak of tshßb nor the initiation of downstream migration, highlighting the importance of endogenous controls. This study brings new insights to the life cycle of Atlantic salmon with the discovery of novel components of the smoltification process, and with implications for conservation.
Key-words: Salmo salar, smoltification, downstream migration, thyrotropin, photoperiod, temperature