Biology subjects

Reichard, T. M.

Publications and source records attributed to Reichard, T. M..

4 recordsLinked to original sources

bioRxiv2024

Seasonality of the estrus cycle in laboratory mice under constant conditions

Seasonality governs every aspect of life in the natural environment. Controlled laboratory settings are intended to keep animals under a constant set of environmental cues with no seasonality. However, prior research suggests that seasonal variation may exist despite aseasonal lab environments. Here, we examined if seasonal reproductive variation was present in a laboratory mouse strain (C57BL/6J) under standard laboratory housing conditions. We found that female C57BL/6J mice exhibited reproductive seasonality mirroring the outside environment, in a controlled "simulated summer" environment. In the winter and spring, females have longer ovulating phases (proestrus and estrus), compared to the fall. Females similarly experience lengthier complete cycles in the spring, with the most rapid cycling occurring in the fall. Additionally, females spent more time in ovulating phases across seasons than previously reported. Laboratory mice are sensitive to external seasonal changes, despite their local environment being light, temperature, and humidity controlled. This may be due to the detection of an unidentified external cue providing information about external seasonal changes. These findings represent just one example of how seasonality may impact mouse physiology in laboratory settings, emphasizing the need to account for such influences in biomedical research.

physiology↗

bioRxiv2024

Sex-specific competitive social feedback amplifies the role of early life contingency in male mice

Contingency (or luck) in early life plays an important role in shaping individuals development. When individuals live within larger societies, social experiences may cause the importance of early contingencies to be magnified or dampened. Here we test the hypothesis that competition magnifies the importance of early contingency in a sex-specific manner by comparing the developmental trajectories of genetically identical, free-living mice who either experienced high levels of territorial competition (males) or did not (females). We show that male territoriality results in a competitive feedback loop that magnifies the importance of early contingency and pushes individuals onto divergent, self-reinforcing life trajectories, while the same process appears absent in females. Our results indicate that the strength of sexual selection may be self-limiting, as within-sex competition increases the importance of early life contingency, thereby reducing the ability of selection to lead to evolution. They also demonstrate the potential for contingency to lead to dramatic differences in life outcomes, even in the absence of any underlying differences in ability ( merit).

evolutionary biology↗

bioRxiv2022

Reproductive state switches the valence of male urinary pheromones in female mice

Internal states shape responses to sensory stimuli. Mammalian female reproductive states are understudied considering they are one of the most regular state changes in the animal kingdom. Here we examine female house mouse preferences toward male odors across the reproductive states of estrus and late-stage pregnancy. In house mice, urine scent marks are salient social odors that convey information about the sex and identity of individuals by major urinary proteins (MUPs). Males secrete a sex-specific pheromonal protein called darcin (MUP20). Additionally, genetically diverse mice secrete unique combinations of MUPs used in individual recognition. Prior work has revealed that male odors are powerful social stimuli for female mice, yet we have a limited understanding of how the valence of such odors change across reproductive states. We discovered a valence shift among estrus and pregnant females toward novel male urine, in which estrus females exhibit preference and pregnant females show strong avoidance. This valence switch also occurs toward darcin alone, providing further support for darcin as a strong sexual signal. However, when presented with familiar male urine, the approach-avoidance response disappears, even when additional darcin is added. In contrast, when an existing identity protein (MUP11) is added to familiar male urine the approach-avoidance response is recovered. This indicates that darcin in the absence of other identity information denotes a novel male and that familiar identity information present in male urine is sufficient to modify responses to darcin. Our findings suggest that the sex and identity information encoded by MUPs are likely processed via distinct, and potentially opposing pathways, that modulate responses toward complex social odor blends. Furthermore, we identify a state-modulated shift in decision-making toward social odors and propose a neural circuit model for this flow of information. These data underscore the importance of physiological state and signal context for interpreting the meaning and importance of social odors.

animal behavior and cognition↗

bioRxiv2022

Scent mark signal investment predicts fight dynamics in house mice

Signals mediate competitive interactions by allowing rival assessment, yet are often energetically expensive to produce. Individuals face tradeoffs when deciding when and where to signal, such that over or under-investing in signaling effort can be costly. One of the key mechanisms maintaining signal reliability is via social costs. While the social costs of over-signaling are well-known, the social costs of under-signaling are underexplored, particularly for dynamic signals. In this study we investigate a dynamic and olfactory-mediated signaling system that is ubiquitous among mammals: scent marking. Male house mice territorially scent mark their environment with metabolically costly urine marks. While competitive male mice are thought to deposit abundant scent marks in the environment, we recently identified a cohort of low-marking males that win fights. Whereas there are clear energetic costs to investing in urine signals in mice, we hypothesized that there may be social costs imposed on individuals who under-invest in signaling. Here we find that scent mark investment predicts fight dynamics. Despite fight outcome being unambiguous, aggressive intensity varies considerably across trials. Males that produce fewer scent marks engage in more intense fights that take longer to resolve. This effect appears to be driven by an unwillingness among losers to acquiesce to weakly signaling winners. We therefore find evidence for rival assessment of scent marks as well as social costs to under-signaling, which supports existing hypotheses for the importance of social punishment in maintaining optimal signaling equilibria. Our results further highlight the possibility of diverse signaling strategies in house mice.

ecology↗