Sleep Arrhythmia in the Eusocial Naked Mole-Rat

Psychology Department, McMaster University, Hamilton, Ontario, Canada.
The Science of Nature (Impact Factor: 2.1). 07/1994; 81(6):272-5. DOI: 10.1007/BF01131581
Source: PubMed
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    • "The study of activity patterns in subterranean mammals has been traditionally addressed to rodent species (see among the others Nevo et al. 1982, Bennet 1992, Rado et al. 1993, Davis-Walton & Sherman 1994, Ben-Shlomo et al. 1995, Lovegrove & Papenfus 1995, Oster et al. 2002, Zelová et al. 2009, Lövy et al. 2013), while little is known about the activity patterns of subterranean insectivores (Godfrey 1955, Mellanby 1967, Harvey 1976, Gorman & Stone 1990, Loy et al. 1992, Hennicke 1997, Macdonald et al. 1997, Borroni et al. 1999). This lack of data is mostly related to the many difficulties in capturing, handling and monitoring subterranean insectivores. "
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    ABSTRACT: The study of activity patterns in subterranean mammals has been poorly explored in subterranean insectivores. This is especially true for the rare and elusive blind mole Talpa caeca. A field work devoted to collect data on life history traits of the blind mole was run in a montane pasture in Southern Italy (1549 m a.s.l.). Plastic barrel-like traps were placed in actively used mole tunnels and checked regularly at 6 h intervals for two sessions of nine consecutive days, for a total 1500 trap-nights. No moles were captured alive, but signs of mole activity at trap sites (traps filled with ground) were regularly recorded. A video recorded inside a trap confirmed that moles fill the traps with soil as part of trap avoidance behavior. Activity at trap sites was analyzed as a binomial variable, considering the rate of filled traps vs. the number of armed traps at each 6 h trap-checking intervals. Activity showed a polyphasic pattern typical of moles, but differently from other species, activity was more concentrated in the central part of the day (12.00-18.00). Results suggest a specific adaptation to local environmental conditions and body size.
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    ABSTRACT: Circadian activity parameters of 53 white-tailed antelope ground squirrels, Ammospermophilus leucurus, were measured to determine the role of the suprachiasmatic nuclei (SCN) pacemaker in their health and survival. Wheel-running activity was monitored in the laboratory with 44 individuals to document the presence of free-running circadian rhythms and ability to entrain to light-dark cycles. Twenty-two individuals were returned to the desert site of origin, including 12 intact control animals and 10 animals whose circadian timing had been disrupted by SCN-lesioning. Time of activity was recorded continuously for 15 days in a large outdoor enclosure by a motion detector, a microchip transponder detector, and video surveillance. An unplanned nighttime attack by a feral cat resulted in the death of 60% of the SCN-lesioned animals and 29% of the control animals in the enclosure. Surface activity of SCN-lesioned animals at the food cache occurred both in daytime and at night, ranging from 16.0% nighttime activity for one partially lesioned individual to 52.1% for one completely lesioned animal. Controls were strongly day-active, with nighttime surface trips constituting only 0-1.3% of all excursions to the cache. Nine wild free-ranging individuals, including one with a radiotransmitter collar, were exclusively day-active. One of the functions of the SCN in mammals may be to reduce activity of animals during times that are unfavorable for activity.
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    ABSTRACT: The mole rat is a solitary, subterranean and photoperiodic rodent. We investigated its rest activity behavior under several lighting conditions, complemented our observations with light-induced c-fos expression, and compared the activity behavior of two chromosomal forms (2n = 58 and 60). The 26 mole rats had a clear overall preference for activity in the light or dark period, but prolonged recordings in five individuals showed that the initial preference was not stable in the nocturnal animals, they became diurnal. A 6-h advance of the light-dark (LD) cycle induced a shift of activity and the previous LD preference was reestablished. The large daily variability of activity onset did not allow this study to determine whether the animals were entrained to the LD cycle upon release into constant darkness (DD) or whether activity had been masked by light. The period of the motor activity rhythm in DD free ran in more than 50% of the animals. No differences in activity were observed between the two karyotypes. Immunohistochemistry for c-fos expression in the nucleus suprachiasmaticus at different circadian times showed that c-fos was induced only in animals exposed to a 1-h light pulse during the subjective night, but not during the subjective day or in control animals in the absence of a light pulse. The large intra- and inter-individual variability in daily motor activity both in LD and in DD suggest only a weak photic entrainment of the circadian clock to light of approximately 100 lux, and possibly a weak regulation of behavior by the circadian clock.
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