| Budget Amount *help |
¥5,070,000 (Direct Cost: ¥3,900,000、Indirect Cost: ¥1,170,000)
Fiscal Year 2016: ¥1,560,000 (Direct Cost: ¥1,200,000、Indirect Cost: ¥360,000)
Fiscal Year 2015: ¥1,560,000 (Direct Cost: ¥1,200,000、Indirect Cost: ¥360,000)
Fiscal Year 2014: ¥1,950,000 (Direct Cost: ¥1,500,000、Indirect Cost: ¥450,000)
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| Outline of Final Research Achievements |
We have focused on morphological evolution of the mammalian middle ear and have reported that the tympanic membrane (TM), consisting of the external auditory meatus (EAM) and first pharyngeal pouch, evolved independently in mammalian and diapsid (modern reptiles and birds) lineages. In this study, we compare TM formation along the anterior-posterior axis of pharyngeal arches in mouse and chick embryos. In mouse, TM is formed in the first pharyngeal arch (PA1) and this arch plays a crucial role in TM formation. By contrast, the EAM begins to invaginate at the surface ectoderm of the second pharyngeal arch (PA2) in chick, and the entire TM is formed in PA2. These results indicate that the classical idea of TM formation is not correct in either animal and further strengthen the idea of independent origin of the TM during amniote evolution.
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