Genetic control of startle behavior in medaka fish.
Genetic polymorphisms are thought to generate intraspecific behavioral diversities, both within and among populations. The mechanisms underlying genetic control of behavioral properties, however, remain unclear in wild-type vertebrates, including humans. To explore this issue, we used diverse inbred strains of medaka fish (Oryzias latipes) established from the same and different local populations. Medaka exhibit a startle response to a visual stimulus (extinction of illumination) by rapidly bending their bodies (C-start) 20-ms after the stimulus presentation. We measured the rates of the response to repeated stimuli (1-s interval, 40 times) among four inbred strains, HNI-I, HNI-II, HO5, and Hd-rR-II1, and quantified two properties of the startle response: sensitivity (response rate to the first stimulus) and attenuation of the response probability with repeated stimulus presentation. Among the four strains, the greatest differences in these properties were detected between HNI-II and Hd-rR-II1. HNI-II exhibited high sensitivity (approximately 80%) and no attenuation, while Hd-rR-II1 exhibited low sensitivity (approximately 50%) and almost complete attenuation after only five stimulus presentations. Our findings suggested behavioral diversity of the startle response within a local population as well as among different populations. Linkage analysis with F2 progeny between HNI-II and Hd-rR-II1 detected quantitative trait loci (QTL) highly related to attenuation, but not to sensitivity, with a maximum logarithm of odds score of 11.82 on linkage group 16. The three genotypes (homozygous for HNI-II and Hd-rR-II1 alleles, and heterozygous) at the marker nearest the QTL correlated with attenuation. Our findings are the first to suggest that a single genomic region might be sufficient to generate individual differences in startle behavior between wild-type strains. Further identification of genetic polymorphisms that define the behavioral trait will contribute to our understanding of the neural mechanisms underlying behavioral diversity, allowing us to investigate the adaptive significance of intraspecific behavioral polymorphisms of the startle response.
Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Bunkyo, Tokyo, Japan.
Satomi
S
Tsuboko
Laboratory of Bioresources, National Institute for Basic Biology, Okazaki, Aichi, Japan; National Institute for Basic Biology Center of the Interuniversity Bio-Backup Project, National Institute for Basic Biology, Okazaki, Aichi, Japan.
Tetsuaki
T
Kimura
Model Fish Genomics Resource, Genetic Strains Research Center, National Institute of Genetics, Mishima, Shizuoka, Japan; Department of Biology, Keio University, Yokohama, Kanagawa, Japan.
Minori
M
Shinya
Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Bunkyo, Tokyo, Japan; Department of Physiology, Tokyo Women's Medical University School of Medicine, Shinjuku, Tokyo, Japan.
Yuji
Y
Suehiro
Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Bunkyo, Tokyo, Japan; Laboratory of Bioresources, National Institute for Basic Biology, Okazaki, Aichi, Japan.
Teruhiro
T
Okuyama
Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Bunkyo, Tokyo, Japan.
Atsuko
A
Shimada
Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Bunkyo, Tokyo, Japan.
Hiroyuki
H
Takeda
Laboratory of Bioresources, National Institute for Basic Biology, Okazaki, Aichi, Japan; National Institute for Basic Biology Center of the Interuniversity Bio-Backup Project, National Institute for Basic Biology, Okazaki, Aichi, Japan.
Kiyoshi
K
Naruse
Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Bunkyo, Tokyo, Japan.
Takeo
T
Kubo
Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Bunkyo, Tokyo, Japan.
Hideaki
H
Takeuchi
D000818:Animals; D001522:Behavior, Animal; D003433:Crosses, Genetic; D016678:Genome; D005838:Genotype; D009068:Movement; D016017:Odds Ratio; D009990:Oryzias / Q000235:genetics*; D010775:Photic Stimulation; D011110:Polymorphism, Genetic; D040641:Quantitative Trait Loci; D013216:Reflex, Startle / Q000235:genetics*; D014741:Video Recording