Molting in the Djungarian hamster (<i>Phodopus sungorus</i> Pallas): Seasonal or continuous process?

Kuhlmann, Michael; Clemen, Günter; Schlatt, Stefan

doi:10.1002/jez.a.10211

Cited by 13 publications

(15 citation statements)

References 22 publications

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“…Investigation of pelage characteristics in Siberian hamsters has been largely restricted to changes in fur color: transfer of Siberian hamsters to SDs induces a molt from the summer agouti pelage to a white winter coat. Some added insulation is likely achieved by a lengthening of hairs on the dorsal surface of SD-housed Siberian hamsters (12,20); the lengths of abdominal hairs appear to be unchanged (20). No differences were detected in dorsal hair density (number of hairs per hair funnel) and a decrease was noted in ventral hair density of SD-exposed males compared with long-day (LD)-exposed males (20).…”

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confidence: 90%

“…The absence of changes in the number of hairs per hair funnel in SD males (20) does not preclude changes in the length/thickness of the hairs, spacing between hair follicles, number of hair follicles, and proportion of hair types, each of which can alter fur mass per unit area of skin (fur density); the latter likely constitutes a more functional measure of pelage density than the number of hairs per hair funnel (hair density). Molting patches are present on the skin of LD and SD hamsters, suggesting that Siberian hamsters undergo a continuous, rather than a seasonal, molt (20). Thus the process by which Siberian hamsters transition between the summer and winter pelage is not clear and appears to be different from that of most species investigated.…”

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confidence: 97%

“…Some added insulation is likely achieved by a lengthening of hairs on the dorsal surface of SD-housed Siberian hamsters (12,20); the lengths of abdominal hairs appear to be unchanged (20). No differences were detected in dorsal hair density (number of hairs per hair funnel) and a decrease was noted in ventral hair density of SD-exposed males compared with long-day (LD)-exposed males (20). Figala et al (8), however, noted an increase in ventral pelage density in SD hamsters but did not provide a quantitative measure.…”

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confidence: 99%

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Photoperiodic and hormonal influences on fur density and regrowth in two hamster species

Paul

George

Zucker

et al. 2007

American Journal of Physiology-Regulatory, Integrative and Comp

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Temperate and boreal mammals undergo seasonal changes in pelage that facilitate thermoregulation in winter and summer. We investigated photoperiodic influences on pelage characteristics of male Siberian and Syrian hamsters. Fur density (mg fur/cm2 skin) was measured by weighing the shavings of fur patches removed from the dorsal and ventral surfaces of hamsters maintained in long days (LDs) or transferred to short days (SDs). Patches were reshaved 3 wk later to assess fur regrowth (mg regrown fur/cm2 skin). Fur density was greater in SD than in LD Siberian hamsters after 11 wk of differential phototreatment. The onset of increased fur density in SDs was accompanied by a transient increase in fur regrowth (11-14 wk on the dorsal surface and 7-10 and 11-14 wk on the ventral surface), suggestive of a seasonal molting process. Fur density, body mass, and pelage color of Siberian hamsters returned to values characteristic of LD males after a similar duration of prolonged (>27 wk) SD treatment and appear to be regulated by a similar or common interval-timing mechanism. In Syrian hamsters, dorsal fur density, fur regrowth, and hair lengths were greater in SD than in LD males. Castration increased and testosterone (T) treatment decreased dorsal and ventral fur regrowth in LD and SD hamsters, but the effects of T manipulations on fur density were limited to a decrease in dorsal fur density after T treatment. Decreased circulating T in SDs likely contributes to the seasonal molt of male hamsters by increasing the rate of fur growth during the transition to the winter pelage.

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Photoperiodic and hormonal influences on fur density and regrowth in two hamster species

Paul

George

Zucker

et al. 2007

American Journal of Physiology-Regulatory, Integrative and Comp

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“…In the process of acclimatization, animals undergo morphological and physiological changes that facilitate winter survival. They can increase body insulation (Cherry and Verner, 1975;Rinehart-Whitt and Pagels, 2000;Kuhlmann et al, 2003), increase or decrease body mass (m b ) (Morrison, 1960;Hoffmann, 1973;Armitage et al, 1976;Heldmaier et al, 2004), increase m b -specific metabolic rate (Heldmaier and Steinlechner, 1981a) and increase the efficiency of heat production, especially by means of non-shivering thermogenesis (NST) (Heldmaier and Buchberger, 1985;Merritt et al, 2001;Bao et al, 2002). In winter, animals stay active or enter daily or seasonal torpor (Hoffmann, 1973;Lyman, 1982b;Körtner and Geiser, 2000;Heldmaier et al, 2004).…”

Section: Introductionmentioning

confidence: 99%

“…Many morphological and physiological adaptations like reduced m b , white pelage and daily torpor reduce its total energy requirements in winter (Figala et al, 1973;Hoffmann, 1973;Heldmaier and Steinlechner, 1981a;Heldmaier and Steinlechner, 1981b;Ruf and Heldmaier, 1992;Ruf et al, 1993;Kuhlmann et al, 2003). Daily torpor occurs as the last response to winter conditions, after a decrease in m b and moulting (Heldmaier and Steinlechner, 1981a).…”

Section: Introductionmentioning

confidence: 99%

Social thermoregulation and torpor in the Siberian hamster

Jefimow

Głabska

Wojciechowski

2011

Journal of Experimental Biology

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SUMMARYSocial thermoregulation and huddling bring about energy benefits to animals sharing a nest because of the smaller surface-tovolume ratio of a huddle and the higher local temperature in the nest. We tested whether living in groups and huddling affect daily torpor, metabolic rate and seasonal changes in the body mass of a small heterothermic rodent, the Siberian hamster (Phodopus sungorus), housed under semi-natural conditions both singly and in groups of four litter-mates. We predicted that in hamsters housed in groups: (1) synchronized torpor bouts would be longer and deeper than non-synchronized ones but shallower than in solitary hamsters, (2) seasonal variations in metabolic rate would be lower than in solitary hamsters, and (3) the winter decrease in body mass would be smaller in grouped than in singly housed hamsters. We found that group housing led to a smaller decrease in body mass in winter, and affected the length and depth of daily torpor. In group-living hamsters more than 50% of all torpor episodes were synchronized and torpid animals were often found in huddles formed of all cage-mates. The longest and deepest torpor bouts in groups were recorded when all animals in a group entered torpor simultaneously. Although the minimum body temperature during torpor was higher, torpor duration was slightly longer than in solitary hamsters. We did not record significant differences in the body mass-adjusted rate of oxygen consumption between solitary and grouped animals, either in the cold or at the lower critical temperature. We conclude that social thermoregulation enables maintenance of a larger body mass, and thus a larger body fat content, which can ensure better body condition at the beginning of the reproductive season.

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Thermal acclimation and nutritional history affect the oxidation of different classes of exogenous nutrients in Siberian hamsters, Phodopus sungorus

et al. 2014

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During acclimatization to winter, changes in morphology and physiology combined with changes in diet may affect how animals use the nutrients they ingest. To study (a) how thermal acclimation and (b) nutritional history affect the rates at which Siberian hamsters (Phodopus sungorus) oxidize different classes of dietary nutrients, we conducted two trials in which we fed hamsters one of three (13) C-labeled compounds, that is, glucose, leucine, or palmitic acid. We predicted that under acute cold stress (3 hr at 2°C) hamsters previously acclimated to cold temperatures (10°C) for 3 weeks would have higher resting metabolic rate (RMR) and would oxidize a greater proportion of dietary fatty acids than animals acclimated to 21°C. We also investigated how chronic nutritional stress affects how hamsters use dietary nutrients. To examine this, hamsters were fed four different diets (control, low protein, low lipid, and low-glycemic index) for 2 weeks. During cold challenges, hamsters previously acclimated to cold exhibited higher thermal conductance and RMR, and also oxidized more exogenous palmitic acid during the postprandial phase than animals acclimated to 21°C. In the nutritional stress trial, hamsters fed the low protein diet oxidized more exogenous glucose, but not more exogenous palmitic acid than the control group. The use of (13) C-labeled metabolic tracers combined with breath testing demonstrated that both thermal and nutritional history results in significant changes in the extent to which animals oxidize dietary nutrients during the postprandial period.

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Molting in the Djungarian hamster (Phodopus sungorus Pallas): Seasonal or continuous process?

Cited by 13 publications

References 22 publications

Photoperiodic and hormonal influences on fur density and regrowth in two hamster species

Photoperiodic and hormonal influences on fur density and regrowth in two hamster species

Social thermoregulation and torpor in the Siberian hamster

Thermal acclimation and nutritional history affect the oxidation of different classes of exogenous nutrients in Siberian hamsters, Phodopus sungorus

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