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Tail reduction process during human embryonic development
Author(s) -
Tojima Sayaka,
Makishima Haruyuki,
Takakuwa Tetsuya,
Yamada Shigehito
Publication year - 2018
Publication title -
journal of anatomy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.932
H-Index - 118
eISSN - 1469-7580
pISSN - 0021-8782
DOI - 10.1111/joa.12774
Subject(s) - amniote , biology , embryonic stem cell , embryogenesis , process (computing) , morphogenesis , embryo , anatomy , reduction (mathematics) , evolutionary biology , microbiology and biotechnology , genetics , computer science , vertebrate , gene , mathematics , geometry , operating system
Although the human tail is completely absent at birth, the embryonic tail is formed just as in other tailed amniotes. Since all morphological variations are created from variations in developmental processes, elucidation of the tail reduction process during embryonic development may be necessary to clarify the human evolutionary process. The tail has also been of great interest to the medical community. The congenital anomaly referred to as ‘human tail’, i.e. the occurrence of a tail‐like structure, has been reported and was thought to represent a vestige of the embryonic tail; however, this hypothesis has not been verified. Accordingly, in this study, we aimed to establish a new method to visualize all somites in an embryo. We used sagittal‐sectioned embryos from Carnegie Stage ( CS ) 13 to CS 23. All samples were obtained from the Congenital Anomaly Research Center, Kyoto University, Japan. Combining photomicroscopy and three‐dimensional reconstruction, we clearly visualized and labeled all somites. We found that the number of somites peaked at CS 16 and dramatically decreased by approximately five somites. Tail reduction with a decrease in somites has also been observed in other short‐tailed amniotes; thus, this result suggested the possibility that there is a common mechanism for morphogenesis of short tails in amniote species. Additionally, our findings provided important insights into the cause of the congenital anomaly known as ‘human tail’.