Dataset Information

Rhythmic 24 h variation of core body temperature and locomotor activity in a subterranean rodent (Ctenomys aff. knighti), the tuco-tuco.

ABSTRACT: The tuco-tuco Ctenomys aff. knighti is a subterranean rodent which inhabits a semi-arid area in Northwestern Argentina. Although they live in underground burrows where environmental cycles are attenuated, they display robust, 24 h locomotor activity rhythms that are synchronized by light/dark cycles, both in laboratory and field conditions. The underground environment also poses energetic challenges (e.g. high-energy demands of digging, hypoxia, high humidity, low food availability) that have motivated thermoregulation studies in several subterranean rodent species. By using chronobiological protocols, the present work aims to contribute towards these studies by exploring day-night variations of thermoregulatory functions in tuco-tucos, starting with body temperature and its temporal relationship to locomotor activity. Animals showed daily, 24 h body temperature rhythms that persisted even in constant darkness and temperature, synchronizing to a daily light/dark cycle, with highest values occurring during darkness hours. The range of oscillation of body temperature was slightly lower than those reported for similar-sized and dark-active rodents. Most rhythmic parameters, such as period and phase, did not change upon removal of the running wheel. Body temperature and locomotor activity rhythms were robustly associated in time. The former persisted even after removal of the acute effects of intense activity on body temperature by a statistical method. Finally, regression gradients between body temperature and activity were higher in the beginning of the night, suggesting day-night variation in thermal conductance and heat production. Consideration of these day-night variations in thermoregulatory processes is beneficial for further studies on thermoregulation and energetics of subterranean rodents.

SUBMITTER: Tachinardi P

PROVIDER: S-EPMC3893220 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature

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Rhythmic 24 h variation of core body temperature and locomotor activity in a subterranean rodent (Ctenomys aff. knighti), the tuco-tuco.

Tachinardi Patricia P Bicudo José Eduardo Wilken JE Oda Gisele Akemi GA Valentinuzzi Verónica Sandra VS

PloS one 20140115 1

The tuco-tuco Ctenomys aff. knighti is a subterranean rodent which inhabits a semi-arid area in Northwestern Argentina. Although they live in underground burrows where environmental cycles are attenuated, they display robust, 24 h locomotor activity rhythms that are synchronized by light/dark cycles, both in laboratory and field conditions. The underground environment also poses energetic challenges (e.g. high-energy demands of digging, hypoxia, high humidity, low food availability) that have mo ...[more]

PMID: 24454916

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Project description:Tuco-tucos (Ctenomys spp.) are subterranean rodents that produce territorial, high intensity long-range vocalizations (LRVs) of broadband and low frequency that are essential for long-distance communication between individuals in different tunnel systems. Despite their importance, the development of LRVs remains poorly understood. In adult Anillaco Tuco-Tucos (Ctenomys sp.) the LRV is composed by two types of syllables (series and individual notes) that are repeated a variable number of times. We studied the development of the LRVs in eight juveniles of the Anillaco Tuco-Tuco ranging from 14-28 to 104-118 days after birth. We (1) tested whether the syllables followed any of three alternative developmental modes (retention of juvenile vocalizations, modification of juvenile precursors or de novo appearance in adults), (2) evaluated the development of structural and acoustic features of syllables, and (3) tested the prediction that juveniles should produce a greater proportion of atypical series in precursors of the LRV than adults, due to lack maturation and/or precise coupling of neuromuscular and anatomical structures. The LRV of the Anillaco Tuco-Tuco exhibited a mixed developmental mode: while series developed from juvenile precursors whose acoustic features gradually approached those of adults, individual notes appeared later in the ontogeny and de novo with acoustic features indistinguishable from those of adults. The number of series per vocalization increased through development and varied from one to 25 in juvenile males and from one to six in juvenile females. The structure of the most common series type (triad) did not exhibit ontogenetic changes and was present as such at the onset of the emission of vocalizations. On the contrary, acoustic features of juvenile triad notes changed with age in both sexes (duration 90% increased through development, while bandwidth 90% and peak frequency decreased). Furthermore, juveniles emitted a higher proportion of atypical series than adults (7.4% vs. 0.3%), as expected in the development of any complex behavior that requires practice to be mastered. The maturation of the LRV occurred well before the sexual maturation, presumably due to the protracted time needed to acquire or build a burrow system long before mating is possible. We propose that protracted vocal development is another component in the slow developmental strategy of Ctenomys and subterranean rodents in general.

Project description:The underground environment poses particular communication challenges for subterranean rodents. Some loud and low-pitched acoustic signals that can travel long distances are appropriate for long-range underground communication and have been suggested to be territorial signals. Long-range vocalizations (LRVs) are important in long-distance communication in Ctenomys tuco-tucos. We characterized the LRV of the Anillaco Tuco-Tuco (Ctenomys sp.) using recordings from free-living individuals and described the behavioral context in which this vocalization was produced during laboratory staged encounters between individuals of both sexes. Long-range calls of Anillaco tuco-tucos are low-frequency, broad-band, loud, and long sounds composed by the repetition of two syllable types: series (formed by notes and soft-notes) and individual notes. All vocalizations were initiated with series, but not all had individual notes. Males were heavier than females and gave significantly lower-pitched vocalizations, but acoustic features were independent of body mass in males. The pronounced variation among individuals in the arrangement and number of syllables and the existence of three types of series (dyads, triads, and tetrads), created a diverse collection of syntactic patterns in vocalizations that would provide the opportunity to encode multiple types of information. The existence of complex syntactic patterns and the description of soft-notes represent new aspects of the vocal communication of Ctenomys. Long-distance vocalizations by Anillaco Tuco-Tucos appear to be territorial signals used mostly in male-male interactions. First, emission of LRVs resulted in de-escalation or space-keeping in male-male and male-female encounters in laboratory experiments. Second, these vocalizations were produced most frequently (in the field and in the lab) by males in our study population. Third, males produced LRVs with greater frequency during male-male encounters compared to male-female encounters. Finally, males appear to have larger home ranges that were more spatially segregated than those of females, suggesting that males may have greater need for long-distance signals that advertise their presence. Due to their apparent rarity, the function and acoustic features of LRV in female tuco-tucos remain inadequately known.

Project description:While most studies of the impacts of climate change have investigated shifts in the spatial distribution of organisms, temporal shifts in the time of activity is another important adjustment made by animals in a changing world. Due to the importance of light and temperature cycles in shaping activity patterns, studies of activity patterns of organisms that inhabit extreme environments with respect to the 24-hour cyclicity of Earth have the potential to provide important insights into the interrelationships among abiotic variables, behaviour and physiology. Our previous laboratory studies with Argentinean tuco-tucos from the Monte desert (Ctenomys aff. knighti) show that these subterranean rodents display circadian activity/rest rhythms that can be synchronized by artificial light/dark cycles. Direct observations indicate that tuco-tucos emerge mainly for foraging and for removal of soil from their burrows. Here we used bio-logging devices for individual, long-term recording of daily activity/rest (accelerometry) and time on surface (light-loggers) of six tuco-tucos maintained in outdoor semi-natural enclosures. Environmental variables were measured simultaneously. Activity bouts were detected both during day and night but 77% of the highest values happened during the daytime and 47% of them coincided with time on surface. Statistical analyses indicate time of day and temperature as the main environmental factors modulating time on surface. In this context, the total duration that these subterranean animals spent on surface was high during the winter, averaging 3 h per day and time on surface occurred when underground temperature was lowest. Finally, transport of these animals to the indoor laboratory and subsequent assessment of their activity rhythms under constant darkness revealed a switch in the timing of activity. Plasticity of activity timing is not uncommon among desert rodents and may be adaptive in changing environments, such as the desert where this species lives.

Dataset Information

Rhythmic 24 h variation of core body temperature and locomotor activity in a subterranean rodent (Ctenomys aff. knighti), the tuco-tuco.

Publications

Rhythmic 24 h variation of core body temperature and locomotor activity in a subterranean rodent (Ctenomys aff. knighti), the tuco-tuco.

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