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

Transient and permanent gene transfer into the brain of the teleost fish medaka (Oryzias latipes) using human adenovirus and the Cre-loxP system

AbstractIn this study, we demonstrated that human type-5 adenovirus infected the brain of the teleost fish, medaka (Oryzias latipes), in vivo. Injection of adenoviral vector into the mesencephalic ventricle of medaka larvae induced the expression of reporter genes in some parts of the telencephalon, the periventricular area of the mesencephalon and diencephalon, and the cerebellum. Additionally, the Cre-loxP system works in medaka brains using transgenic medaka carrying a vector containing DsRed2, flanked by loxP sites under control of the β-actin promoter and downstream promoterless enhanced green fluorescent protein (EGFP). We demonstrated that the presence of green fluorescence depended on injection of adenoviral vector expressing the Cre gene and confirmed that EGFP mRNA was transcribed in the virus-injected larvae

Development of ethnographic digital collections

Περιέχει το πλήρες κείμενοΟι λαογραφικές συλλογές αποτελούν πολύτιμη πηγή μελέτης, εξερεύνησης και αξιολόγησης των εθνικών στερεοτύπων των διαφόρων διαμερισμάτων μιας χώρας, δεδομένου ότι στις συλλογές είναι καταχωρημένα ανόθευτα και πηγαία τα εγχώρια εθνοχαρακτηριστικά τους. Κατά κύριο λόγο η λαογραφία αναφέρεται στους μύθους, τα τραγούδια, τη μουσική, τα έθιμα, τη χειροτεχνία, την ενδυμασία, την αρχιτεκτονική και την προφορική παράδοση μιας κοινότητας. Η ιδιαιτερότητα και η ποικιλία ενός τομέα όπως της λαογραφίας δικαιολογεί απόλυτα την ύπαρξη συλλογών και υπο-συλλογών σύνθετης δομής και σημασιολογίας, όπως αυτές που αναφέρουμε παραπάνω. Επομένως η ανάπτυξη ψηφιακών συλλογών απαιτεί τη διατήρηση των στοιχείων που χρειάζονται για: (α) την περιγραφή του περιεχομένου της κάθε συλλογής χωριστά και (β) τη σωστή απεικόνιση της δομής των αντικειμένων στο εσωτερικό αυτής. Στόχος της εργασίας αυτής είναι η παρουσίαση μιας μεθοδολογίας για την ανάπτυξη ενός περιγραφικού μοντέλου μεταδεδομένων για λαογραφικές συλλογές. Το μοντέλο θα αποτελέσει βασικό εργαλείο για την περιγραφή του ψηφιοποιημένου λαογραφικού υλικού, την πρόσβαση σε αυτό από κατανεμημένους χρήστες και φυσικά την επικοινωνία του με άλλα συστήματα. Επιπλέον θα συμβάλλει στη διασύνδεση σύνθετων συλλογών και των αντικειμένων που περιλαμβάνουν είτε σημασιολογικά, είτε χρονικά, είτε θεματικά είτε με οποιονδήποτε άλλο τρόπο απαιτεί η φύση των συλλογών και οι ανάγκες των χρηστών

CRISPR-Cas9システムを用いた味覚受容体発現調節物質のスクリーニング系の開発

Taste recognition mediated by taste receptors is critical for the survival of animals in nature and is an important determinant of nutritional status and quality of life in humans. However, many factors including aging, diabetes, zinc deficiency, infection with influenza or cold viruses, and chemotherapy can trigger dysgeusia, for which a standard treatment has not been established. We here established an engineered strain of medaka (Oryzias latipes) that expresses green fluorescent protein (GFP) from the endogenous taste 1 receptor 3 (T1R3) gene locus with the use of the CRISPR-Cas9 system. This T1R3-GFP knock-in (KI) strain allows direct visualization of expression from this locus by monitoring of GFP fluorescence. The pattern of GFP expression in the T1R3-GFP KI fish thus mimicked that of endogenous T1R3 gene expression. Furthermore, exposure of T1R3-GFP KI medaka to water containing monosodium glutamate or the anticancer agent 5-fluorouracil resulted in an increase or decrease, respectively, in GFP fluorescence intensity, effects that also recapitulated those on T1R3 mRNA abundance. Finally, screening for agents that affect GFP fluorescence intensity in T1R3-GFP KI medaka identified tryptophan as an amino acid that increases T1R3 gene expression. The establishment of this screening system for taste receptor expression in medaka provides a new tool for the development of potential therapeutic agents for dysgeusia

Production of the medaka derived from vitrified whole testes by germ cell transplantation

The medaka (Oryzias latipes) is a teleost model distinguished from other model organisms by the presence of inbred strains, wild stocks, and related species. Cryopreservation guarantees preservation of these unique biological resources. However, because of their large size, cryopreservation techniques for their eggs and embryos have not been established. In the present study, we established a methodology to produce functional gametes from cryopreserved testicular cells (TCs). Whole testes taken from medaka were cryopreserved by vitrification. After thawing, the cells dissociated from cryopreserved testicular tissues were intraperitoneally transplanted into sterile triploid hatchlings. Some cells, presumably spermatogonial stem cells, migrated into the genital ridges of recipients and resulted in the production of eggs or sperm, based on sex of the recipient. Mating of recipients resulted in successful production of cryopreserved TC-derived offspring. We successfully produced individuals from the Kaga inbred line, an endangered wild population in Tokyo, and a sub-fertile mutant (wnt4b(-/-)) from cryopreserved their TCs. This methodology facilitates semi-permanent preservation of various medaka strains

Mutant analyses reveal different functions of fgfr1 in medaka and zebrafish despite conserved ligand–receptor relationships

AbstractMedaka (Oryzias latipes) is a small freshwater teleost that provides an excellent developmental genetic model complementary to zebrafish. Our recent mutagenesis screening using medaka identified headfish (hdf) which is characterized by the absence of trunk and tail structures with nearly normal head including the midbrain–hindbrain boundary (MHB). Positional-candidate cloning revealed that the hdf mutation causes a functionally null form of Fgfr1. The fgfr1hdf is thus the first fgf receptor mutant in fish. Although FGF signaling has been implicated in mesoderm induction, mesoderm is induced normally in the fgfr1hdf mutant, but subsequently, mutant embryos fail to maintain the mesoderm, leading to defects in mesoderm derivatives, especially in trunk and tail. Furthermore, we found that morpholino knockdown of medaka fgf8 resulted in a phenotype identical to the fgfr1hdf mutant, suggesting that like its mouse counterpart, Fgf8 is a major ligand for Fgfr1 in medaka early embryogenesis. Intriguingly, Fgf8 and Fgfr1 in zebrafish are also suggested to form a major ligand–receptor pair, but their function is much diverged, as the zebrafish fgfr1 morphant and zebrafish fgf8 mutant acerebellar (ace) only fail to develop the MHB, but develop nearly unaffected trunk and tail. These results provide evidence that teleost fish have evolved divergent functions of Fgf8–Fgfr1 while maintaining the ligand–receptor relationships. Comparative analysis using different fish is thus invaluable for shedding light on evolutionary diversification of gene function

Genomic and Phenotypic Characterization of a Wild Medaka Population : Towards the Establishment of an Isogenic Population Genetic Resource in Fish

Oryzias latipes (medaka) has been established as a vertebrate genetic model for more than a century and recently has been rediscovered outside its native Japan. The power of new sequencing methods now makes it possible to reinvigorate medaka genetics, in particular by establishing a near-isogenic panel derived from a single wild population. Here we characterize the genomes of wild medaka catches obtained from a single Southern Japanese population in Kiyosu as a precursor for the establishment of a near-isogenic panel of wild lines. The population is free of significant detrimental population structure and has advantageous linkage disequilibrium properties suitable for the establishment of the proposed panel. Analysis of morphometric traits in five representative inbred strains suggests phenotypic mapping will be feasible in the panel. In addition, high-throughput genome sequencing of these medaka strains confirms their evolutionary relationships on lines of geographic separation and provides further evidence that there has been little significant interbreeding between the Southern and Northern medaka population since the Southern/Northern population split. The sequence data suggest that the Southern Japanese medaka existed as a larger older population that went through a relatively recent bottleneck approximately 10,000 years ago. In addition, we detect patterns of recent positive selection in the Southern population. These data indicate that the genetic structure of the Kiyosu medaka samples is suitable for the establishment of a vertebrate near-isogenic panel and therefore inbreeding of 200 lines based on this population has commenced. Progress of this project can be tracked at http://www.ebi.ac.uk/birney-srv/medaka-ref-panel

Polycystic Kidney Disease in the Medaka (Oryzias latipes) pc Mutant Caused by a Mutation in the Gli-Similar3 (glis3) Gene

Polycystic kidney disease (PKD) is a common hereditary disease in humans. Recent studies have shown an increasing number of ciliary genes that are involved in the pathogenesis of PKD. In this study, the Gli-similar3 (glis3) gene was identified as the causal gene of the medaka pc mutant, a model of PKD. In the pc mutant, a transposon was found to be inserted into the fourth intron of the pc/glis3 gene, causing aberrant splicing of the pc/glis3 mRNA and thus a putatively truncated protein with a defective zinc finger domain. pc/glis3 mRNA is expressed in the epithelial cells of the renal tubules and ducts of the pronephros and mesonephros, and also in the pancreas. Antisense oligonucleotide-mediated knockdown of pc/glis3 resulted in cyst formation in the pronephric tubules of medaka fry. Although three other glis family members, glis1a, glis1b and glis2, were found in the medaka genome, none were expressed in the embryonic or larval kidney. In the pc mutant, the urine flow rate in the pronephros was significantly reduced, which was considered to be a direct cause of renal cyst formation. The cilia on the surface of the renal tubular epithelium were significantly shorter in the pc mutant than in wild-type, suggesting that shortened cilia resulted in a decrease in driving force and, in turn, a reduction in urine flow rate. Most importantly, EGFP-tagged pc/glis3 protein localized in primary cilia as well as in the nucleus when expressed in mouse renal epithelial cells, indicating a strong connection between pc/glis3 and ciliary function. Unlike human patients with GLIS3 mutations, the medaka pc mutant shows none of the symptoms of a pancreatic phenotype, such as impaired insulin expression and/or diabetes, suggesting that the pc mutant may be suitable for use as a kidney-specific model for human GLIS3 patients