The Effects of Thyroxine and Propylthiouracil Treatment on Changes in Body Form Associated with a Possible Developmental Thyroxine Surge During Post-hatching Development of the Tilapia, Oreochromis mossambicus
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概要
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In tilapia, Oreochromis mossambicus, a surge in thyroxine (T_4) begins near the time of complete yolk absorption (10 days after hatching). We were interested in examining the effects of physiological changes in T_4 on growth and body morphology of this species. To this end, starting 3 days after hatching, larvae were immersed in propylthiouracil (PTU, 50 ppm) or in physiological doses of T_4 (2.0, 5.0 and 20 ng/ml of aquarium water). Whole-body thyroid hormone levels and morphometric parameters were determined throughout the first 38 days after hatching. Thyroxine content was significantly increased in larvae exposed to 5.0 or 20 ng/ml T_4 compared with controls, with the highest levels observed during the time of the natural T_4 peak (day 10-28 posthatch). By contrast, T4 content was significantly decreased in PTU-treated larvae at this time. These results indicate a role of the thyroid for the T_4 surge. The T_3 content of larvae exposed to 20 ng/ml T_4 was significantly increased compared with controls. Exposure to T_4 significantly altered body proportions. Both the anal depth to standard length ratio and body area of larvae were significantly increased by 20 ng/ml T_4 treatment and decreased by PTU treatment. This suggests a role of the T_4 surge in the metamorphosis from a slender, elongated body form to a deep-bodied juvenile form. There were no observed effects of hormone treatment on other morphological features that were examined including body weight, standard length, and the rate of yolk-sac absorption.
- 社団法人日本動物学会の論文
- 1993-10-15
著者
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Grau E
Hawaii Inst. Marine Biology Hawaii Usa
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Grau E.gordon
Department Of Zoology And Hawaii Institute Of Marine Biology University Of Hawaii
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Okimoto K.
Department of Zoology and Hawaii Institute of Marine Biology, University of Hawaii
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Weber M.
Department of Zoology and Hawaii Institute of Marine Biology, University of Hawaii
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Grau Gordon
Department of Zoology and Hawaii Institute of Marine Biology, University of Hawaii
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Weber M.
Department Of Zoology And Hawaii Institute Of Marine Biology University Of Hawaii
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Weber M.
Department Of Dental Prosthetics Section Of Dental Materials University Of Technology Aachen
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Okimoto K.
Department Of Zoology And Hawaii Institute Of Marine Biology University Of Hawaii
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Okimoto Darren
Department of Zoology and Hawaii Institute of Marine Biology, University of Hawaii
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Weber Gregory
Department of Zoology and Hawaii Institute of Marine Biology, University of Hawaii
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