Mate-guarding behavior enhances male reproductive success via familiarization with mating partners in medaka fish

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

Mate-guarding behavior enhances male reproductive success via familiarization with mating partners in medaka fish

[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

Upgrading of shielding for rare decay search in CANDLES

In the CANDLES experiment aiming to search for the very rare neutrino-less double beta decays (0νββ) using 48Ca, we introduced a new shielding system for high energy γ-rays from neutron captures in massive materials near the detector, in addition to the background reduction for 232Th decays in the 0νββ target of CaF2 crystals. The method of background reduction and the performance of newly installed shielding system are described

Attenuated Food Anticipatory Activity and Abnormal Circadian Locomotor Rhythms in Rgs16 Knockdown Mice

Regulators of G protein signaling (RGS) are a multi-functional protein family, which functions in part as GTPase-activating proteins (GAPs) of G protein α-subunits to terminate G protein signaling. Previous studies have demonstrated that the Rgs16 transcripts exhibit robust circadian rhythms both in the suprachiasmatic nucleus (SCN), the master circadian light-entrainable oscillator (LEO) of the hypothalamus, and in the liver. To investigate the role of RGS16 in the circadian clock in vivo, we generated two independent transgenic mouse lines using lentiviral vectors expressing short hairpin RNA (shRNA) targeting the Rgs16 mRNA. The knockdown mice demonstrated significantly shorter free-running period of locomotor activity rhythms and reduced total activity as compared to the wild-type siblings. In addition, when feeding was restricted during the daytime, food-entrainable oscillator (FEO)-driven elevated food-anticipatory activity (FAA) observed prior to the scheduled feeding time was significantly attenuated in the knockdown mice. Whereas the restricted feeding phase-advanced the rhythmic expression of the Per2 clock gene in liver and thalamus in the wild-type animals, the above phase shift was not observed in the knockdown mice. This is the first in vivo demonstration that a common regulator of G protein signaling is involved in the two separate, but interactive circadian timing systems, LEO and FEO. The present study also suggests that liver and/or thalamus regulate the food-entrained circadian behavior through G protein-mediated signal transduction pathway(s)

La législation du dépôt légal pendant l’Occupation

La Bibliothèque nationale sous l'Occupation - Des sources pour l'histoire du livre et des collections entre 1940 et 1946Cet article inaugure dans la carnet de blog "La Bibliothèque nationale sous l'Occupation - Des sources pour l'histoire du livre et des collections entre 1940 et 1946", une série sur les évolutions du fonctionnement et de la législation du dépôt légal durant la Seconde Guerre mondiale

La législation du dépôt légal pendant l’Occupation

La Bibliothèque nationale sous l'Occupation - Des sources pour l'histoire du livre et des collections entre 1940 et 1946Cet article inaugure dans la carnet de blog "La Bibliothèque nationale sous l'Occupation - Des sources pour l'histoire du livre et des collections entre 1940 et 1946", une série sur les évolutions du fonctionnement et de la législation du dépôt légal durant la Seconde Guerre mondiale

La législation du dépôt légal pendant l’Occupation

La Bibliothèque nationale sous l'Occupation - Des sources pour l'histoire du livre et des collections entre 1940 et 1946Cet article inaugure dans la carnet de blog "La Bibliothèque nationale sous l'Occupation - Des sources pour l'histoire du livre et des collections entre 1940 et 1946", une série sur les évolutions du fonctionnement et de la législation du dépôt légal durant la Seconde Guerre mondiale

La législation du dépôt légal pendant l’Occupation

La Bibliothèque nationale sous l'Occupation - Des sources pour l'histoire du livre et des collections entre 1940 et 1946Cet article inaugure dans la carnet de blog "La Bibliothèque nationale sous l'Occupation - Des sources pour l'histoire du livre et des collections entre 1940 et 1946", une série sur les évolutions du fonctionnement et de la législation du dépôt légal durant la Seconde Guerre mondiale

La législation du dépôt légal pendant l’Occupation

La Bibliothèque nationale sous l'Occupation - Des sources pour l'histoire du livre et des collections entre 1940 et 1946Cet article inaugure dans la carnet de blog "La Bibliothèque nationale sous l'Occupation - Des sources pour l'histoire du livre et des collections entre 1940 et 1946", une série sur les évolutions du fonctionnement et de la législation du dépôt légal durant la Seconde Guerre mondiale