Comparative development of intercalary elements in the first finger joint of neobatrachians: the origin of arboreal frogs

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K06786
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 45030:Biodiversity and systematics-related
• Research Institution: Hiroshima University
• Principal Investigator: Tazawa Ichiro 広島大学, 両生類研究センター, 助教 (10304388)
• Co-Investigator(Kenkyū-buntansha): 中島 圭介 広島大学, 両生類研究センター, 助教 (60260311)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: intercalary element / 樹上性 / カエル亜目 / 進化 / 起源 / 共通祖先

Outline of Final Research Achievements

We compared the development of intercalary elements (IEs) in the hindlimbs of two distantly related frog species within the suborder Neobatrachia, the Japanese tree frog and the Schlegel's green tree frog. The Japanese tree frog IE was neither stained with Alcian blue nor Alizarin red for some time after metamorphosis, and was only slightly stained with the Alizarin red even in adults. In contrast, the Schlegel's green frog IE stained with Alcian blue before and after metamorphosis and with Alizarin red in adults. Histological observations showed that IEs of both species originated from equivalent sites at equivalent developmental stages. In addition, IEs of both species were found to be composed of cartilaginous tissue.

Free Research Field

進化発生学

Academic Significance and Societal Importance of the Research Achievements

本研究はカエル亜目の遠縁の２種の intercalary element の発生過程を初めて比較したものである．本研究の結果は，両種の指における IE は特定の色素に対する染色性こそ異なるが，共通祖先の同じ組織に由来し，その形成の基本メカニズムは類似していることを示唆している．したがって，カエル亜目の IE が収斂的に進化したのではないという仮説を支持している．これは現生カエル種の９割以上を占めるカエル亜目の共通祖先が樹上性だった可能性を示すものであり，そうであれば自然史学におけるインパクトは大きい．