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Kruger JL, Bhagwandin A, Katandukila JV, Bennett NC, Manger PR. Sleep in the East African root rat, Tachyoryctes splendens. JOURNAL OF EXPERIMENTAL ZOOLOGY. PART A, ECOLOGICAL AND INTEGRATIVE PHYSIOLOGY 2024. [PMID: 38828695 DOI: 10.1002/jez.2839] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2024] [Revised: 05/16/2024] [Accepted: 05/16/2024] [Indexed: 06/05/2024]
Abstract
The present study reports the results of an electrophysiological analysis of sleep in the East African root rat, Tachyoryctes splendens, belonging to the rodent subfamily Spalacinae. Telemetric electroencephalographic (EEG) and electromyographic recordings, with associated video recording, on three root rats over a continuous 72 h period (12 h light/12 h dark cycle) were analyzed. The analysis revealed that the East African root rat has a total sleep time (TST) of 8.9 h per day. Despite this relatively short total sleep time in comparison to fossorial rodents, nonrapid eye movement (non-REM) sleep and rapid eye movement (REM) sleep states showed similar physiological signatures to that observed in other rodents and no unusual sleep states were observed. REM occupied 19.7% of TST, which is within the range observed in other rodents. The root rats were extremely active during the dark period, and appeared to spend much of the light period in quiet wake while maintaining vigilance (as determined from both EEG recordings and behavioral observation). These recordings were made under normocapnic environmental conditions, which contrasts with the hypercapnic environment of their natural burrows.
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Affiliation(s)
- Jean-Leigh Kruger
- School of Anatomical Sciences, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Adhil Bhagwandin
- School of Anatomical Sciences, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Jestina V Katandukila
- Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa
- Department of Zoology and Wildlife Conservation, University of Dar es Salaam, Dar es Salaam, Tanzania
| | - Nigel C Bennett
- Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa
| | - Paul R Manger
- School of Anatomical Sciences, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
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Pleštilová L, Hrouzková E, Burda H, Meheretu Y, Šumbera R. Ear morphology in two root-rat species (genus Tachyoryctes) differing in the degree of fossoriality. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2021; 207:469-478. [PMID: 33956210 DOI: 10.1007/s00359-021-01489-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Revised: 04/20/2021] [Accepted: 04/24/2021] [Indexed: 11/30/2022]
Abstract
It is supposed that the subterranean lifestyle in mammals is reflected in ear morphology and tuning of hearing to low frequencies. We studied two root-rat species to see if their ear morphology reflects the difference in the amount of their surface activity. Whereas the more subterranean Tachyoryctes splendens possesses shorter pinnae as expected, it has smaller bullae compared to the more epigeic Tachyoryctes macrocephalus. The ratio between the eardrum and the stapedial footplate area and the ratio between the mallear and the incudal lever were lower in T. splendens (19.3 ± 0.3 and 1.9 ± 0.0, respectively) than in T. macrocephalus (21.8 ± 0.6 and 2.1 ± 0.1), probably reflecting the latter's higher surface activity. The cochlea in both species has 3.5 coils, yet the basilar membrane is longer in the smaller T. splendens (13.0 ± 0.5 versus 11.4 ± 0.7 mm), which indicates its wider hearing range and/or higher sensitivity (to some frequencies). In both root-rat species, the highest density of outer hair cells (OHC) was in the apical part of the cochlea, while the highest density of inner hair cells (IHC) was in its middle part. This OHC density pattern corresponds with good low-frequency hearing, whereas the IHC pattern suggests sensitivity to higher frequencies.
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Affiliation(s)
- Lucie Pleštilová
- Department of Zoology, Faculty of Science, University of South Bohemia, Branišovská, 1760, 37005, České Budějovice, Czech Republic.
| | - Ema Hrouzková
- Department of Zoology, Faculty of Science, University of South Bohemia, Branišovská, 1760, 37005, České Budějovice, Czech Republic
| | - Hynek Burda
- Department of Game Management and Wildlife Biology, Faculty of Forestry and Wood Sciences, Czech University of Life Sciences, 16521, Praha, Czech Republic
| | - Yonas Meheretu
- Department of Biology, College of Natural and Computational Sciences, University of Mekelle, Mekelle, Ethiopia
| | - Radim Šumbera
- Department of Zoology, Faculty of Science, University of South Bohemia, Branišovská, 1760, 37005, České Budějovice, Czech Republic
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Entrainment of circadian rhythms of locomotor activity by ambient temperature cycles in the dromedary camel. Sci Rep 2020; 10:19515. [PMID: 33177571 PMCID: PMC7658228 DOI: 10.1038/s41598-020-76535-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Accepted: 10/29/2020] [Indexed: 11/08/2022] Open
Abstract
In the dromedary camel, a well-adapted desert mammal, daily ambient temperature (Ta)-cycles have been shown to synchronize the central circadian clock. Such entrainment has been demonstrated by examining two circadian outputs, body temperature and melatonin rhythms. Locomotor activity (LA), another circadian output not yet investigated in the camel, may provide further information on such specific entrainment. To verify if daily LA is an endogenous rhythm and whether the desert Ta-cycle can entrain it, six dromedaries were first kept under total darkness and constant-Ta. Results showed that the LA rhythm free runs with a period of 24.8–24.9 h. After having verified that the light–dark cycle synchronizes LA, camels were subjected to a Ta-cycle with warmer temperatures during subjective days and cooler temperatures during subjective nights. Results showed that the free-running LA rhythm was entrained by the Ta-cycle with a period of exactly 24.0 h, while a 12 h Ta-cycle phase advance induced an inversion of the LA rhythm and advanced the acrophase by 9 h. Similarly, activity onset and offset were significantly advanced. All together, these results demonstrate that the Ta-cycle is a strong zeitgeber, able to entrain the camel LA rhythm, hence corroborating previous results concerning the Ta non-photic synchronization of the circadian master clock.
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Ackermann S, Bennett NC, Katandukila JV, Oosthuizen MK. Circadian rhythms of locomotor activity in captive Emin’s mole-rats,Heliophobius emini(Rodentia: Bathyergidae). J Mammal 2016. [DOI: 10.1093/jmammal/gyw166] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Katandukila JV, Bennett NC. Pattern of ovulation in the East African root rat (Tachyoryctes splendens) from Tanzania: induced or spontaneous ovulator? CAN J ZOOL 2016. [DOI: 10.1139/cjz-2015-0217] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The East African root rat (Tachyoryctes splendens (Rüppell, 1835)) is a solitary subterranean rodent that exhibits a marked seasonal reproduction linked to the bimodal rainfall pattern of East Africa. The current study sets out to determine whether the East African root rat is an induced or spontaneous ovulator. Five wild caught adult females were monitored noninvasively for ovarian cyclicity by measuring urinary progesterone every 2 days over a period of 120 days. Females were subjected to three different experimental treatments, namely, initially singly housed or control (C), nonphysical contact with a male (NPC), and physical contact with a vasectomised male (PC), respectively. The concentration of urinary progesterone was higher during PC than during either NPC or C. The act of coitus appears to be necessary for ovulation to occur in the females. The male East African root rats were found to possess epidermal spines on the penis that can be used to bring about cervical stimulation during coitus. The spines result in the induction of ovulation as has been proposed for other solitary subterranean rodents. The findings from the female progesterone profiles and the assessment of penile morphology suggest that the female East African root rat is an induced ovulator stimulated by penile intromission during coitus.
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Affiliation(s)
- Jestina V. Katandukila
- Departments of Zoology and Entomology, University of Pretoria, Pretoria 0002, Republic of South Africa
- Department of Zoology, College of Natural and Applied Sciences, University of Dar es Salaam, P.O. Box 35064, Dar es Salaam, Tanzania
| | - Nigel C. Bennett
- Departments of Zoology and Entomology, University of Pretoria, Pretoria 0002, Republic of South Africa
- South African Research Chair for Mammal Behavioural Ecology and Physiology, Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, Republic of South Africa
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van der Merwe I, Bennett N, Haim A, Oosthuizen M. Locomotor activity in the Namaqua rock mouse (Micaelamys namaquensis): entrainment by light manipulations. CAN J ZOOL 2014. [DOI: 10.1139/cjz-2014-0161] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The locomotor activity rhythms of wild-caught Namaqua rock mice (Micaelamys namaquensis (A. Smith, 1834)) were examined under four light-cycle regimes to quantitatively describe the daily expression of locomotor activity and to study the innate relationship between activity and the light–dark cycle. Activity was always significantly higher at night than during the day; we note four trends. (1) The LD1 light cycle (12 h light : 12 h dark) established a distinct light-entrained and strongly nocturnal activity rhythm (99.11% nocturnal activity). The activity onset was prompt (zeitgeber time (ZT) 12.2 ± 0.04) and activity continued without any prominent peaks or extended times of rest until the offset of activity at ZT 23.73 ± 0.08. (2) Evidence for the internal maintenance of locomotor activity was obtained from the constant dark cycle (DD) in which locomotor activity free ran (mean τ = 23.89 h) and 77.58% of the activity was expressed during the subjective night. (3) During re-entrainment (LD2; 12 h light : 12 h dark), a nocturnal activity rhythm was re-established (98.65% nocturnal activity). (4) The inversion of the light cycle (DL; 12 h dark : 12 h light) evoked a shift in activity that again revealed dark-induced locomotor activity (95.69% nocturnal activity). Females were consistently more active than males in all of the light cycles, but only under the DD and LD2 cycles were females significantly more active than males. Although this species is considered nocturnal from field observations, information regarding its daily expression of activity and the role of light in its entrainment is lacking. To the best of our knowledge, this study is the first to report quantitatively on the species’ daily rhythm of activity and to investigate its relationship to the light–dark cycle.
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Affiliation(s)
- I. van der Merwe
- Department of Zoology and Entomology, University of Pretoria, Private Bag X20, Hatfield, 0028, South Africa
| | - N.C. Bennett
- Department of Zoology and Entomology, University of Pretoria, Private Bag X20, Hatfield, 0028, South Africa
| | - A. Haim
- The Israeli Center for Interdisciplinary Studies in Chronobiology, University of Haifa, Haifa 31905, Israel
| | - M.K. Oosthuizen
- Department of Zoology and Entomology, University of Pretoria, Private Bag X20, Hatfield, 0028, South Africa
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