2013 Fiscal Year Final Research Report

A study of pupil in Medaka

Research Project

Project/Area Number	24657051
Research Category	Grant-in-Aid for Challenging Exploratory Research
Allocation Type	Single-year Grants
Research Field	Animal physiology/Animal behavior
Research Institution	The University of Tokyo
Principal Investigator	ODA Shoji 東京大学, 新領域創成科学研究科, 准教授 (50266714)
Project Period (FY)	2012-04-01 – 2014-03-31
Keywords	瞳孔 / 自律神経 / メダカ
Research Abstract	Textbooks say that the iris size does not change in most species of teleost, although all vertebrates including Chondrichthyes change the size of iris in response to strong light under control by autonomic nervous system. In this study, employing high-resolution digital image recording and image analysis the size change of iris was examined carefully in a model teleost, medaka (Oryzias latipes). When exposed to strong light, medaka decreased the size of pupil, showing miosis. Moreover, activation of parasympathetic nervous system activity by administration of acetylcholine or tamsulosin induced miosis, strongly suggesting that iris contracts via control by autonomic nervous system in medaka as the same manner as human. Administration of atropine or phenylephrine did not increase the size of pupil, suggesting that the iris of the examined individual expanded maximum presumably because sympathetic nervous activity was thoroughly activated by taking pictures.