Biology subjects

Mason, G.

Publications and source records attributed to Mason, G..

3 recordsLinked to original sources

bioRxiv2026

How does housing quality affect maternal investment and reproduction?

Poor housing is linked to reproductive failure in captive mammals, but the mechanisms are rarely tested. To understand the mechanism behind it, we used DBA/2 mice as models and in conventional housing (CH) and well-resourced housing (WR) across three cohorts (N = 36 sister-pair cages; 6 CH and 6 WR per Cohort). We tested two mutually non-exclusive mechanisms: the energy hypothesis (low maternal body condition, measured as BMI, impairs reproduction) and the stereotypic behaviour (SB) hypothesis (SB competes with reproduction and maternal care regardless of body condition). Housing affected maternal care: WR dams built better nests (p = 0.002), nursed more (p = 0.018) and nursed for more days before weaning (p = 0.023), and their pups tended to be heavier at PND 28 (14.2 vs 12.5 g, p = 0.06). Unexpectedly, all CH dams (7/7) retrieved displaced pups, but no WR dams did (0/8), likely reflecting how the test cage was perceived. But housing did not affect mating, pregnancy, litter size, pup survival or pup weight up to postnatal day (PND) 21. CH females performed about 9 times more SB than WR females before mating, and the difference persisted through lactation. BMI did not differ by housing, so the energy hypothesis was not supported. Adding SB to models weakened housing effects on nest quality and nursing, but SB itself did not significantly predict any outcome. Here, we found that housing quality mainly shapes how dams care for pups during lactation but not their capacity to breed. SB may play a partial role, but that needs better-powered testing. This study supports improving housing for captive breeding programmes now, even though the mechanism remains unknown.

animal behavior and cognition↗

bioRxiv2022

Mechanical compression induces persistent bacterial growth during bacteriophage predation

Although the relationship between bacteria and lytic bacteriophage is fundamentally antagonistic, these microbes not only coexist but thrive side-by-side in myriad ecological environments. The mechanisms by which coexistence is achieved, however, are not fully understood. By examining Escherichia coli and bacteriophage T7 population dynamics at the single-cell and single-virion level using a novel microfluidics-based assay, we observed bacteria growing "persistently" when perfused with high-titer bacteriophage. Persistence occurred at a frequency five orders of magnitude higher than is expected from natural selection of bacteriophage-resistant mutants. Rather, the frequency of persistence was correlated with the degree to which the bacteria were mechanically compressed by the microfluidic perfusion chamber. Using a combination of mutagenesis and fluorescent imaging techniques, we found that compression induces persistence by activating the Rcs phosphorelay pathway, which results in the synthesis of extracellular capsule that sterically blocks bacteriophage adsorption. Other forms of mechanical stimulation also promoted Rcs activity and persistence. These findings have important implications for our understanding of microbial ecology in many important environments, including the gut and the soil, where bacteria grow in confinement. Significance StatementBacteria and bacteriophage form one of the most fundamental and important predator-prey relationships on earth, yet the factors that promote long-term stability of their populations are unknown. Here, we demonstrate that Escherichia coli is able to rapidly grow during bacteriophage predation if they are doing so in spatially confined environments. This discovery revises our understanding of bacteria-bacteriophage population dynamics in many real-world environments where bacteria grow in such environments, such as the gut and the soil. Additionally, this result has critical implications for the potential of antibacterial therapies to function during pathogenesis, when bacteria are also mechanically stimulated.

microbiology↗

bioRxiv2021

Cancer blues? A validated judgment bias task suggests pessimism in nude mice with tumors

In humans, affective states can bias responses to ambiguous information: a phenomenon termed judgment bias (JB). Judgment biases have great potential for assessing affective states in animals, in both animal welfare and biomedical research. New animal JB tasks require construct validation, but for laboratory mice (Mus musculus), the most common research vertebrate, a valid JB task has proved elusive. Here (Experiment 1), we demonstrate construct validity for a novel mouse JB test: an olfactory Go/Go task in which subjects dig for high- or low-value food rewards. In C57BL/6 and Balb/c mice faced with ambiguous cues, latencies to dig were sensitive to high/low welfare housing, environmentally-enriched animals responding with relative optimism through shorter latencies. Illustrating the versatility of a validated JB task across fields of research, it further allowed us to test hypotheses about the mood-altering effects of cancer (Experiment 2). Male nude mice bearing subcutaneous lung adenocarcinomas responded more pessimistically than healthy controls to ambiguous cues. Similar effects were not seen in females, however. To our knowledge, this is the first validation of a mouse JB task and the first demonstration of pessimism in tumor-bearing animals. This task, especially if refined to improve its sensitivity, thus has great potential for investigating mouse welfare, the links between affective state and disease, depression-like states in animals, and hypotheses regarding the neurobiological mechanisms that underlie affect-mediated biases in judgment.

animal behavior and cognition↗