Biology subjects

Shier, D. M.

Publications and source records attributed to Shier, D. M..

2 recordsLinked to original sources

bioRxiv2025

Hormonal and Environmental Drivers of Spermiation in the Endangered Mountain Yellow-Legged Frog (Rana muscosa): Toward Biologically Informed Assisted Reproductive Technologies.

Amphibians are among the most threatened vertebrates, yet assisted reproductive technologies (ARTs) remain underutilised in their conservation. We developed and evaluated a biologically relevant, non-lethal sperm collection protocol for Rana muscosa, a critically endangered frog in a long-term conservation breeding program. Thirteen hormone treatments were tested across six post-injection time points, and sperm quality was assessed via concentration, motility, osmolality, and pH. Generalised linear mixed models revealed that gonadotropin-releasing hormone (GnRHa) alone significantly outperformed hCG-based regimens. The 3 {micro}g/g GnRHa dose yielded the highest sperm concentration and sustained motility from 3 to 24 hours post-injection. Motility was highest under moderately acidic (pH 6.5-7.0) and hypoosmotic (75-100 mOsm/kg) conditions. To support decision-making, we applied a refined Wildlife Sperm Index (WSI) that weights motility and concentration as primary functional-yield traits, with motility given greater relative weight given its direct role in fertilisation, and treats pH and osmolality as secondary environmental-compatibility traits. Under this revised composite score, 3 {micro}g/g GnRHa achieved the highest overall WSI score, outperforming 2 {micro}g/g and 4 {micro}g/g GnRHa, which ranked second and third, respectively, despite their more favourable pH and osmolality profiles. These findings provide the first evidence-based ART protocol for R. muscosa and offer a transferable framework for optimising gamete collection, IVF, and cryopreservation in line with other amphibian species, advancing both genetic management and species recovery goals.

zoology↗

bioRxiv2023

Environmental change drives multi-generational shifts in the gut microbiome that mirror changing animal fitness

Gut microbiomes can dramatically affect host health and fitness and can also be highly dynamic in response to changing environmental conditions. This intricate interplay between gut microbiota, environmental pressures, and host health necessitates accounting for all these variables when predicting the response of animals to a changing environment. These predictions are of broad concern but are highly relevant to conservation biology, and more specifically to populations transitioning from the wild to human care for the purposes of ex situ breeding programs. Captivity can dramatically alter both host-associated microbial communities and host health, but the dynamics of how the host and microbiome transition between the wild and captive state--within and across generations--are not well described. Here, we evaluate the microbiome and host fitness metrics for Pacific pocket mice (Perognathus longimembris pacificus) during the establishment of an ex situ conservation breeding program to characterize how pocket mice and their microbiomes respond to the environmental pressures of captivity across five generations. We found that the microbiome assumes a novel, stable conformation after two to three generations in captivity and that the patterns observed in the transitioning microbiota mirror the patterns of transitioning hosts weight and reproductive metrics. Moreover, we identify several microbial taxa which are correlated with successful reproduction. Our results provide insight not only into the effects of captivity but can be broadly applicable for understanding the effects of environmental change on organisms and their gut microbiota, which we propose may require multiple generations to reach an alternative stable state.

ecology↗