Melatonin secretion in a strictly subterranean mammal, the Damaraland mole‐rat (<i>Cryptomys damarensis</i>)

Richter, Trevor; Malpaux, Benoît; Fleming, Patricia A.; Molteno, A. J.; Bennett, Nigel C.

doi:10.1017/s0952836903004254

Cited by 16 publications

(11 citation statements)

References 37 publications

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“…The blood plasma melatonin rhythm, which is of pineal origin, shows mean daytime levels of PMC that are lower than those values measured at night. This is consistent with many other mammals, such as the Syrian (Mesocricetus auratus) and the Djungarian (Phodopus sungorus) hamster [18,19], the valley pocket gopher (Thomomys bottae) [2] and the Damaraland mole-rat (C. damarensis) [12] to compare some rodents living in a similar habitat. In experiment 1, levels of PMC exhibited an endogenous rhythm that conforms to the findings of locomotory activity patterns of this species measured via e-mitter, IR captors and running wheel [14].…”

Section: Discussionsupporting

confidence: 85%

“…The presence of light resulted in low levels of PMCs at T12 on day 2 in LL animals, with no difference between the two sample times, while showing a small standard error. This result contrasts findings with a sister taxon the Damaraland mole-rat [12] as well as the valley pocket gopher [2] but is consistent, for example, with the laboratory rat [23]. According to Reiter et al [2] and Richter et al [12] the valley pocket gopher and Damaraland mole-rat are diurnal species.…”

Section: Discussioncontrasting

confidence: 57%

“…The majority of subterranean mammals that have been studied are seasonal hibernators which do not cover the openings of their underground burrows and which emerge onto the surface frequently during the day and are therefore exposed to light. The first subterranean species studied not fitting these criteria was the valley pocket gopher (Thomomys bottae) [2] and more recently the Damaraland mole-rat (C. damarensis) [12]. The present study investigates the highveld mole-rat (C. h. pretoriae), which like the other two species, is subterranean, covers the openings of its burrows and does not hibernate.…”

Section: Introductionmentioning

confidence: 99%

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The endogenous rhythm of plasma melatonin and its regulation by light in the highveld mole‐rat (Cryptomys hottentotus pretoriae): a microphthalmic, seasonally breeding rodent

Gutjahr

Rensburg

Malpaux

et al. 2004

Journal of Pineal Research

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The day- and night-time levels of plasma melatonin were measured in adult male and female highveld mole-rats, Cryptomys hottentotus pretoriae. This study aimed to assess whether melatonin secretion in this nocturnal, strictly subterranean but seasonally breeding rodent has a day-night rhythm and whether that rhythm is circadian and can be modified by photoperiod. In experiment 1, a day-night rhythm of plasma melatonin was found in all animals housed on a 12L:12D schedule, with significantly higher concentrations in the dark (D) compared with the light (L) phase. The increment of plasma melatonin concentration at night was the same on days 1 and 2 for animals in the control group and animals transferred to constant dark. The animals transferred to constant light substantially reduced the amplitude of the melatonin rhythm on day 2. This suggests that the endogenous melatonin rhythm in C. h. pretoriae has a circadian pattern, which can be synchronized by photoperiod and inhibited by exposure to light at night. In experiment 2, the concentration of plasma melatonin in animals kept under 14L:10D (long day, LD) conditions differed significantly from animals on 10L:14D (short day, SD). This finding supports the notion that C. h. pretoriae is sensitive to changes in day length.

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Section: Discussionsupporting

confidence: 85%

Section: Discussioncontrasting

confidence: 57%

Section: Introductionmentioning

confidence: 99%

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The endogenous rhythm of plasma melatonin and its regulation by light in the highveld mole‐rat (Cryptomys hottentotus pretoriae): a microphthalmic, seasonally breeding rodent

Gutjahr

Rensburg

Malpaux

et al. 2004

Journal of Pineal Research

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“…All species thus far investigated display locomotor activity rhythms that can be entrained to light (Hart et al, 2004;Oosthuizen et al, 2003;Riccio & Goldman, 2000a;Schöttner et al, 2006;Vasicek et al, 2005a). In addition, melatonin secretion (Gutjahr et al, 2004, Hart et al, 2004Richter et al, 2003;Vasicek et al, 2005b) and body temperature (Lovegrove & Muir, 1996;Riccio & Goldman, 2000b) also show rhythmic cycles and light can suppress melatonin secretion in the blind mole-rat (Zubidat et al, 2009). …”

Section: Introductionmentioning

confidence: 99%

PHOTIC INDUCTION OF Fos IN THE SUPRACHIASMATIC NUCLEUS OF AFRICAN MOLE-RATS: RESPONSES TO INCREASING IRRADIANCE

Oosthuizen

Bennett

Cooper

2010

Chronobiology International

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African mole-rats (family Bathyergidae) are strictly subterranean rodent species that are rarely exposed to environmental light. Morphological and physiological adaptations to the underground environment include a severely reduced eye size and regressed visual system. Responses of the circadian system to light, however, appear to be intact, since mole-rats are able to entrain their circadian activity rhythms to the light-dark cycle and light induces Fos expression in the suprachiasmatic nucleus (SCN). Social organization varies from solitary species to highly elaborated eusocial structures, characterized by a distinct division of labor and in which one reproductive female regulates the behavior and reproductive physiology of other individuals in the colony. The authors studied light-induced Fos expression in the SCN to increasing light intensities in four mole-rat species, ranging from strictly solitary to highly social. In the solitary Cape mole-rat, light induces significant Fos expression in the SCN, and the number of Fos-immunopositive cells increases with increasing light intensity. In contrast, Fos induction in the SCN of social species was slightly greater than, but not statistically different from, the dark-control animals as is typical of most rodents. One species showed a trend for an increase in expression with increased light, whereas a second species showed no trend in expression. In the naked mole-rat, Fos expression appeared higher in the dark-controls than in the animals exposed to light, although the differences in Fos expression were not significant. These results suggest a gradient in the sensitivity of the circadian system to light in mole-rats, with a higher percentage of individuals that are unresponsive to light in correlation with the degree of sociality. In highly social species, such as the naked mole-rat that live in a relatively stable subterranean milieu in terms of food availability, temperature, constant darkness, and devoid of 24-h cyclic environmental cues, the temporal coordination of rest-wake activities may be dependent on social interactions and social status rather than on photic regulation of the circadian timing system.

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“…All species investigated thus far display locomotor activity rhythms loosely entrained to light under experimental conditions (e.g. Lovegrove & Papenfus 1995;Riccio & Goldman 2000;Oosthuizen et al 2003;Hart et al 2004;Vasicek et al 2005;Schottner et al 2006), and circadian rhythms of melatonin secretion (Richter et al 2003;Gutjahr et al 2004;Vasicek et al 2005) and body temperature (Lovegrove & Muir 1996;Riccio & Goldman 2000). Nevertheless, field studies have suggested that burrow temperature could also be an important stimulus for entraining circadian activity under natural conditions ( Skl ıba et al 2007( Skl ıba et al , 2014.…”

Section: Introductionmentioning

confidence: 99%

Behavioural Tests Reveal Severe Visual Deficits in the Strictly Subterranean African Mole‐Rats (Bathyergidae) but Efficient Vision in the Fossorial Rodent Coruro (Spalacopus cyanus, Octodontidae)

et al. 2016

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Vision has long been considered purposeless in the dark underground ecotope. However, recent anatomical studies revealed an unexpected diversity of ocular and retinal features and various degrees of development of the visual system in mammals with predominantly subterranean activity, and have suggested retention of basic visual capabilities even in some strictly subterranean mammals such as the African mole-rats. Behavioural tests assessing image-forming vision have not yet been conducted in subterranean mammals. Here, we investigated the visual capacities in three species of the African mole-rats, namely the giant mole-rat Fukomys mechowii, the Mashona mole-rat Fukomys darlingi and the silvery mole-rat Heliophobius argenteocinereus, in the fossorial coruro Spalacopus cyanus and the inbred C57L/J mouse. The behavioural assays performed in this study revealed severe visual deficits in all three species of mole-rats. The absence of the visual placing reflex suggested impairment of either image-forming vision or visuomotor integration. The random choice between the shallow and the deep side of a visual cliff clearly demonstrated inability of molerats to perceive depth. The nesting assay did not yield conclusive evidence regarding the capacity for visually guided spatial orientation in the only tested species, the giant mole-rat. In contrast, both the coruro and the mouse exhibited a clear placing reaction and preferred the shallow side of the visual cliff, implying functional image-forming vision. Thus, the behavioural data gathered in this study show that vision is seriously compromised in the strictly subterranean, congenitally microphthalmic African mole-rats but efficient (i.e. comparable to that of surface-dwelling rodents) in a species with regular surface activity, the coruro.

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Melatonin secretion in a strictly subterranean mammal, the Damaraland mole‐rat (Cryptomys damarensis)

Cited by 16 publications

References 37 publications

The endogenous rhythm of plasma melatonin and its regulation by light in the highveld mole‐rat (Cryptomys hottentotus pretoriae): a microphthalmic, seasonally breeding rodent

The endogenous rhythm of plasma melatonin and its regulation by light in the highveld mole‐rat (Cryptomys hottentotus pretoriae): a microphthalmic, seasonally breeding rodent

PHOTIC INDUCTION OF Fos IN THE SUPRACHIASMATIC NUCLEUS OF AFRICAN MOLE-RATS: RESPONSES TO INCREASING IRRADIANCE

Behavioural Tests Reveal Severe Visual Deficits in the Strictly Subterranean African Mole‐Rats (Bathyergidae) but Efficient Vision in the Fossorial Rodent Coruro (Spalacopus cyanus, Octodontidae)

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