title: Mate-guarding behavior enhances male reproductive success via familiarization with mating partners in medaka fish.
abstract: BACKGROUND
  Male-male competition and female mating preference are major mechanisms of sexual selection, which influences individual fitness. How male-male competition affects female preference, however, remains poorly understood. Under laboratory conditions, medaka (Oryzias latipes) males compete to position themselves between a rival male and the female (mate-guarding) in triadic relationships (male, male, and female). In addition, females prefer to mate with visually familiar males. In the present study, to examine whether mate-guarding affects female preference via visual familiarization, we established a novel behavioral test to simultaneously quantify visual familiarization of focal males with females and mate-guarding against rival males. In addition, we investigated the effect of familiarization on male reproductive success in triadic relationships.
  
  
  RESULTS
  Three fish (female, male, male) were placed separately in a transparent three-chamber tank, which allowed the male in the center (near male) to maintain closer proximity to the female than the other male (far male). Placement of the wild-type male in the center blocked visual familiarization of the far male by the female via mate-guarding. In contrast, placement of an arginine-vasotocin receptor mutant male, which exhibits mate-guarding deficits, in the center, allowing for maintaining close proximity to the female, did not block familiarization of the far male by the female. We also demonstrated that the reproductive success of males was significantly decreased by depriving females visual familiarization with the males.
  
  
  CONCLUSIONS
  Our findings indicated that, at least in triadic relationships, dominance in mate-guarding, not simply close proximity, allows males to gain familiarity with the female over their rivals, which may enhance female preference for the dominant male. These findings focusing on the triadic relationships of medaka may contribute to our understanding of the adaptive significance of persistent mate-guarding, as well as female preference for familiar mates.
authors.affiliation: Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo, Japan ; Laboratory of Bioresources, National Institute for Basic Biology, Okazaki, Aichi Japan.
authors.forename: Saori
authors.initials: S
authors.lastname: Yokoi
authors.affiliation: Division of Applied Biosciences, Graduate School of Agriculture, Kyoto University, Kyoto, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Ansai
authors.affiliation: Division of Applied Biosciences, Graduate School of Agriculture, Kyoto University, Kyoto, Japan.
authors.forename: Masato
authors.initials: M
authors.lastname: Kinoshita
authors.affiliation: Laboratory of Bioresources, National Institute for Basic Biology, Okazaki, Aichi Japan.
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Naruse
authors.affiliation: Laboratory of Bioresources, National Institute for Basic Biology, Okazaki, Aichi Japan.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Kamei
authors.affiliation: Center for Translational Social Neuroscience, Department of Psychiatry and Behavioral Sciences, Yerkes National Primate Research Center, Emory University, Atlanta, USA.
authors.forename: Larry J
authors.initials: LJ
authors.lastname: Young
authors.affiliation: Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo, Japan ; The Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, USA.
authors.forename: Teruhiro
authors.initials: T
authors.lastname: Okuyama
authors.affiliation: Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo, Japan ; Graduate School of Natural Science and Technology, Okayama University, Okayama, Japan.
authors.forename: Hideaki
authors.initials: H
authors.lastname: Takeuchi
keywords: Familiarity; Female preference; Mate-guarding; Medaka fish