Temporal Dissociation Between Activity and Body Temperature Rhythms of a Subterranean Rodent (Ctenomys famosus) in Field Enclosures

Abstract

Several wild rodents, such as the subterranean tuco-tucos ( Ctenomys famosus), switch their time of activity from diurnal to nocturnal when they are transferred from field to the laboratory. Nevertheless, in most studies, different methods to measure activity in each of these conditions were used, which raised the question of whether the detected change in activity timing could be an artifact. Because locomotor activity and body temperature (Tb) rhythms in rodents are tightly synchronized and because abdominal Tb loggers can provide continuous measurements across field and laboratory, we monitored Tb as a proxy of activity in tuco-tucos transferred from a semi-field enclosure to constant lab conditions. In the first stage of this study (“Tb-only group,” 2012-2016), we verified high incidence (55%, n = 20) of arrhythmicity, with no consistent diurnal Tb rhythms in tuco-tucos maintained under semi-field conditions. Because these results were discrepant from subsequent findings using miniature accelerometers (portable activity loggers), which showed diurnal activity patterns in natural conditions ( n = 10, “Activity-only group,” 2016-2017), we also investigated, in the present study, whether the tight association between activity and Tb would be sustained outside the lab. To verify this, we measured activity and Tb simultaneously across laboratory and semi-field deploying both accelerometers and Tb loggers to each animal. These measurements ( n = 11, “Tb + activity group,” 2019-2022) confirmed diurnality of locomotor activity and revealed an unexpected loosening of the temporal association between Tb and activity rhythms in the field enclosures, which is otherwise robustly tight in the laboratory.

Molecular circadian rhythms are robust in marine annelids lacking rhythmic behavior

“…Investigating the factors that shape phenotypic and rhythmic diversity in an integrative way will help to understand how animals adapt to specific habitats and how these factors can contribute to overall population fitness. Differences between individuals and between levels of organization are common features of biological rhythm in various clades and habitats [59,[70][71][72], and individual differences in behavioral patterns directly feed back to the experienced ("realized") environmental cycles used for entrainment [73][74][75]. It is thus important to treat biological variation not as "background noise," but as an additional aspect of biodiversity that needs to be considered in both the mechanistic and the ecological context [28,76].…”