Kenagy, G. J. | bioRxiv Science

bioRxiv2026

Impaired non-shivering thermogenesis in the desert-dwelling antelope ground squirrel

Adaptations in animals occupying environments of extreme cold or heat offer unique insights into thermoregulation. The antelope ground squirrel, a desert-dwelling rodent situated within a clade of hibernators, provides a notable example of these thermoregulatory extremes. As a non-hibernator closely related to hibernators, antelope ground squirrels may represent a rare case of trait reversal, with a striking ability to maintain core body temperatures exceeding 43{degrees}C while displaying poor tolerance to prolonged cold. Here, we explore the genetic and phenotypic basis of these unique traits by generating the first genome assembly for this species, which we use to conduct comparative genomics across the squirrel family. We complement this with acute and chronic cold-exposure experiments coupled with transcriptomic profiling of thermogenic organs: brown adipose tissue, white adipose tissue, and skeletal muscle. Together, these findings reveal a shift away from non-shivering thermogenesis toward metabolically demanding shivering thermogenesis, a perilous strategy for sustained heat generation.

evolutionary biology↗

bioRxiv2024

Lack of circadian entrainment and limited nocturnal plasticity in response to a cyclic aversive stimulus in a diurnal rodent, the antelope ground squirrel (Ammospermophilus leucurus)

Recent studies have shown that cyclic aversive stimuli, such as random footshocks, act as a nonphotic zeitgeber to entrain circadian behaviors in nocturnal rodents, a pattern termed "fear entrainment". However, it remains unknown whether diurnal species exhibit similar plasticity in behavioral timing. This study aimed to determine if antelope ground squirrels (Ammospermophilus leucurus; AGS), a naturally diurnal rodent, can also shift their activity patterns to cyclic aversive stimuli. We conducted two experiments with 20 AGS housed in custom cages featuring a safe nesting area and a separate foraging area (for feeding and drinking), rendered aversive by presentation of unsignaled, time-specific footshocks. In the first experiment, animals were subjected to a 12:12 light-dark (LD) cycle. One group experienced aversion during the light phase, while the control group received the same treatment during the dark phase. In the second experiment, a 16:8 LD cycle was used, and animals were divided into three groups with the foraging area rendered aversive either during the first or second half of the light phase or during the dark phase. Following each of these treatments, animals were released into constant darkness (DD) to assess the phase and period of free-running rhythms. Contrary to previous findings in nocturnal rodents, AGS did not exhibit consistent shifts in activity to avoid footshocks. Most animals maintained their normal diurnal activity, with only minor and inconsistent phase shifts. In experiment two, animals exposed to footshocks during half of the light phase also failed to reliably shift activity to the opposite "safe" portion of the light phase. Together, these findings show AGS lack the ability to entrain to cyclic aversive stimuli or become nocturnal; this result suggests a lack of substantial plasticity in activity timing. These results highlight the importance of considering species-specific differences in nonphotic circadian entrainment and temporal niche plasticity.

animal behavior and cognition↗