Title (eng)
Modulation and consistency of ultrasonic vocalizations in the Eastern European house mouse (Mus musculus musculus) and sensor data to improve detection of mild lameness in dairy cattle
functions and translational value
Author
Maria Adelaide Marconi
Degree supervisor
Dustin J. Penn
Degree supervisor
Peter Balazs
Description (eng)
PhD thesis - University of Veterinary Medicine Vienna - 2023
Abstract (eng)
Research on the communication of house mice has largely focused on olfactory signals, whereas their acoustic signals have received relatively little attention until recent years. I investigated the expression and functions of chemosensory and acoustic signals of Eastern European house mice (Mus musculus subsp. musculus), and particularly the functions of male courtship vocalizations. Male mice emit ultrasonic vocalizations (USVs) during courtship, which potentially influence their mating and reproductive success; however, evidence for this hypothesis has been lacking. My aims were to determine the effect of male pheromones and courtship vocalizations on male reproductive success, and I focused my research on wild derived Mus musculus (henceforth “wild mice”). To determine what kind of information is contained in male USVs (signaling functions), which females could use to assess the state and identity of potential mates, I also investigated whether USVs reliably signal males' sexual arousal and individual identity. Due to the enormous time and effort required for analyzing mouse vocalizations, I also collaborated on research aimed at developing better methods for automatic USV detection and classification. Below, I summarize the main aims and results from each of the chapters in my dissertation. The first chapter provides results from a study that we conducted to test the effect of chemical signals on reproductive success of wild house mice living in seminatural conditions. We found that males increased the excretion of certain volatile and involatile pheromones only once they became socially dominant and acquired a territory, and dominant males had higher reproductive success than subordinates. Females discriminated and showed a preferential attraction towards the urinary scent of dominant versus subordinate males, but they showed no preferences for male urine with higher concentrations of involatile major urinary proteins (MUPs). Our study provides the first results to show that pheromone production correlates with male reproductive success for any mammal. They also raise important caveats for studying the regulation and functions of the pheromones of male mice in laboratory conditions. The second chapter presents the results from an experiment that we conducted to test whether males alter the emission of USVs after exposure to a female (i.e., socio-sexual priming). Early studies on male laboratory mice suggested that exposure to a female, or female odor enhances the rate of male USV emission, and that USVs therefore provide a reliable indicator of sexual arousal and interest in mating; however, the evidence for this hypothesis has been mixed. In this study, we implemented an improved version of a method that we developed to improve detection of USVs (Automated Mouse Ultrasound Detector or AMUD), which is the first step during data processing. Our results show that the socio-sexual priming increased the number and the types of USVs that males emitted, and the effects were long-lasting. This study provides the first evidence for socio-sexual priming of USV emission in wild house mice and the first to show that priming enhances the diversity as well as the rate of male USV emission. The third chapter reports the results of an experiment in which we aimed to test whether mice modulate USV production depending upon the genetic relatedness of a potential mate, and whether courtship USV emission correlates with a breeding pair’s subsequent reproductive success. We found that courtship USVs are differently modulated in different consecutive social contexts (indirect and subsequent direct social contact) and that males increased the number and spectral complexity of vocalizations during direct interactions. In this latter context, USV number and modulation correlated with reproductive success and relatedness to the female partner: mating pairs of genetically unrelated individuals emitted USVs with higher duration and spectral complexity and showed a higher reproductive success compared to pairs that were closely related, whose USVs were shorter and spectrally simple and had a lower reproductive success. Our results provide the first evidence that mice modulate USV emission during courtship depending upon genetic relatedness of a potential mate and that USV emission (rate and types) correlate with their subsequent reproductive success. In the fourth chapter, our goal was to test the hypothesis that male courtship USVs provide cues of individual identity (individual vocal signatures). We first tested whether USVs change once males are provided with a female odor stimulus; and then we evaluated the variation in the quantity and quality of USVs within individuals versus among individuals over three consecutive weeks. The males rarely vocalized until presented with female odor, and then individual males consistently increased the number and spectral complexity of USVs. After the presentation of female odor, we found that the spectrotemporal features of male USVs differed between individuals and mice could be classified according to their “vocalizing style” with a striking difference between low versus high vocalizers. We found that some males have a distinct vocal repertoire that is repeatable over time and that some spectrotemporal features of their USV structure could potentially be used by conspecifics for individual recognition. This study provides the first evidence that male mice increase the numbers and types of USVs upon investigating female odor, and also the first evidence that male USVs contain individual signatures that are consistent over time. In the fifth chapter, we aimed to cross-validate findings from different strains of laboratory mice, and we analyzed the USV emission and the social behavior of three strains, commonly used in studies on neurodevelopmental disorders (NDDs). Our results showed strain differences in the number and duration of USVs, the onset of the peak in the calling rate during neonatal age, and also sex and strain differences in the number of vocalizations and repertoire composition during adulthood during same sex (i.e., female-female) and opposite-sex interactions. For the first time, we showed that: (1) there is a large phenotypic variation among strains in their social and communicative profile (i.e., number and duration of social investigations, vocalizations and spectrotemporal features of USVs); (2) strain C57/B6 emitted the lowest number of USVs that were spectrally simple and performed the lowest number of partner investigations; and (3) CD1 outbred strain showed an intermediate sociocommunicative profile compared to the two inbred strains. Our results highlight the differences in the behavior and vocalizations among strains of laboratory mice and importance of choosing the appropriate strain to conduct experiments on socio-communicative profiles in mice. In the sixth chapter, we developed a new method for automatically classifying different types of USVs, and compared its performance with other methods. Manual classification of USVs requires a tremendous amount of time, even for trained researchers, and therefore, we aimed to develop a new automatic USV classification method that is more reliable and generalizable than the current methods that are available. Our new method combines bootstrapping and ensemble machine learning. We found that it can accurately classify USVs into 12 different types (though accuracy was improved by pooling more types), and that it outperformed all other methods. This is the first study to systematically compare different automatic USV detection and classification methods and evaluate their performance, and we also provide a new method that now provides the state-of-the-art tool for USV classification. In summary, the main goals of my research were to investigate the adaptive functions of chemical and acoustic signals of house mice in terms of their effects on reproductive success. The results of these studies provide novel evidence that male pheromones and vocalizations influence reproductive success. To better understand why females are attracted to male USVs, and what kind of information they could provide to potential mates, I also tested hypotheses about their signaling functions. The results of these studies provide novel evidence that courtship USVs provide reliable information about a male's individual identity (individual vocal signatures) and their state (sexual arousal). We presented a novel non-invasive tool to profile animal models used for NDDs and implemented a novel detection system and classification method for analyzing USVs in both, wild and domesticated mice. Results from studies on laboratory mice have provided many important and interesting findings, but as we have shown, the results from one strain cannot necessarily be extrapolated to other strains or their wild counter parts. Therefore, in the future, more studies on wild house mice are necessary to address questions about the ecological relevance and adaptive significance of their complex chemical and acoustic signals.
Description (deu)
PhD Arbeit - Veterinärmedizinische Universität Wien - 2023
Type (eng)
Dissertation
Language
[eng]
Persistent identifier
https://phaidra.vetmeduni.ac.at/o:4717
AC number
AC17667331
DOI
10.34876/jhb0-ry40
Number of pages
184
Date issued
2023
License
All rights reserved