Thyroid function and olfactory responses to L-alanine during induced smoltification in Atlantic salmon, Salmo salar

• Published in: Canadian Journal of Fisheries and Aquatic Sciences
• Main Authors: Morin, P -P, Hara, T J, Eales, J G
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1997
• Subjects: Aquatic Science; Ecology, Evolution, Behavior and Systematics; Atlantic salmon; Salmo salar
• Online Access: http://dx.doi.org/10.1139/f96-309; http://www.nrcresearchpress.com/doi/pdf/10.1139/f96-309

For 5 weeks starting in mid-February we examined developmental correlations between external smolt features, plasma thyroid hormone levels, and olfactory responses in Atlantic salmon transferred from 0.9 to 11°C and exposed to a 16 h light : 8 h dark (16L) or an 8 h light : 16 h dark (8L) photoperiod. In 16L fish, external smolt features developed to 80% of full state, plasma L-thyroxine (T 4 ) surged at week 3, but there were no changes in plasma 3,5,3 prime -triiodo-L-thyronine, olfactory bulb electroencephalographic (EEG), or olfactory epithelium electro-olfactographic (EOG) activities in response to nasal stimulation with L-alanine (10 -9 to 10 -5 M). In 8L fish, external smolt features were arrested at 40% of full state, plasma T 4 showed no surge, EOG activity increased modestly, but EEG activity increased markedly at weeks 3 and 4. Thus, under the particular photoperiod and temperature conditions imposed in this study in February and March, enhanced olfactory activity can develop in premigratory Atlantic salmon independently of external smolt features or a significant surge in plasma T 4 .