title: Histopathology of a wavy medaka.
abstract: Wavy medakas are medakas that exhibit spinal curvature characterized by dorsoventrally curved vertebrae. We found a spontaneous wavy medaka in our experimental stock and subjected it to a histopathological examination. Macroscopically, the wavy medaka's spine formed an M shape, and its vertebrae displayed a dorsoventral curvature that started at the third vertebral bone. Microscopically, the vertebral cavities were filled with fibrous tissue, which was similar to that seen in the central parts of the intervertebral discs of a normal medaka. The vertebral joints were composed of vacuolated notochord cells without intervertebral disc formation. These changes were also observed in the caudal region, which exhibited less curvature. In the normal medaka, the intervertebral discs form via the regression of the notochord that plays a key role in the development of vertebrae and disc formation. We concluded that notochordal subinvolution had induced intervertebral disc dysplasia, leading to lordokyphosis, in the wavy medaka.
authors.affiliation: Biological Research Laboratories, Nissan Chemical Industries, Ltd., 1470 Shiraoka, Shiraoka, Saitama 349-0294, Japan.
authors.forename: Kota
authors.initials: K
authors.lastname: Irie
authors.affiliation: Biological Research Laboratories, Nissan Chemical Industries, Ltd., 1470 Shiraoka, Shiraoka, Saitama 349-0294, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Kuroda
authors.affiliation: Biological Research Laboratories, Nissan Chemical Industries, Ltd., 1470 Shiraoka, Shiraoka, Saitama 349-0294, Japan.
authors.forename: Norihiko
authors.initials: N
authors.lastname: Mimori
authors.affiliation: Biological Research Laboratories, Nissan Chemical Industries, Ltd., 1470 Shiraoka, Shiraoka, Saitama 349-0294, Japan.
authors.forename: Seigo
authors.initials: S
authors.lastname: Hayashi
authors.affiliation: Biological Research Laboratories, Nissan Chemical Industries, Ltd., 1470 Shiraoka, Shiraoka, Saitama 349-0294, Japan.
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Abe
authors.affiliation: Biological Research Laboratories, Nissan Chemical Industries, Ltd., 1470 Shiraoka, Shiraoka, Saitama 349-0294, Japan.
authors.forename: Naho
authors.initials: N
authors.lastname: Tsuji
authors.affiliation: Department of Veterinary Laboratory Medicine, School of Veterinary Medicine, Faculty of Agriculture, Tottori University Biological Research Laboratories, 4-101 Minami, Koyama, Tottori 680-8550, Japan.
authors.forename: Akihiko
authors.initials: A
authors.lastname: Sugiyama
authors.affiliation: Biological Research Laboratories, Nissan Chemical Industries, Ltd., 1470 Shiraoka, Shiraoka, Saitama 349-0294, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Furukawa
keywords: intervertebral disc; lordokyphosis; notochord; spinal curvature; wavy medaka