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  • 1
    In: Parasite, EDP Sciences, Vol. 19, No. 4 ( 2012-11), p. 331-340
    Type of Medium: Online Resource
    ISSN: 1252-607X , 1776-1042
    Language: English
    Publisher: EDP Sciences
    Publication Date: 2012
    detail.hit.zdb_id: 2278575-9
    SSG: 12
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  • 2
    Online Resource
    Online Resource
    Canadian Science Publishing ; 2015
    In:  Canadian Journal of Zoology Vol. 93, No. 5 ( 2015-05), p. 345-351
    In: Canadian Journal of Zoology, Canadian Science Publishing, Vol. 93, No. 5 ( 2015-05), p. 345-351
    Abstract: Stable isotope analysis is frequently applied as a tool to examine dietary patterns in animals. However, some of the underlying assumptions associated with using this approach are increasingly being questioned. We carried out a controlled diet experiment on the southern African spiny mouse (Acomys spinosissimus Peters, 1852) to test a number of aspects relating to these assumptions and also examine the hypothesis that stable isotopes, especially δ 15 N, can be used to provide evidence of nutritional stress. We compared the δ 13 C and δ 15 N values of livers and blood from animals that were fed ad libitum with animals undergoing a 10% reduction in food supply. Food-restricted animals showed no significant difference in δ 15 N; however, δ 13 C values of both liver and blood were depleted. Restricted animals also had a significantly lower C:N ratio. We examined the role of lipids and found following lipid extraction that both livers and lipids still showed the same separation in carbon values. Tissue–diet discrimination values were also calculated and found to be higher for both Δ 13 C and Δ 15 N compared with other mice species. Empirical values for discrimination rates were then compared with values calculated using an alternative method based on employing generic values and were found to be dissimilar, suggesting the use of generic values are not always appropriate. Our results highlight the need for greater understanding of the assumptions associated with using stable isotope analysis to examine diet and we suggest that studying a single species under captive conditions presents an ideal method to begin to test these hypotheses.
    Type of Medium: Online Resource
    ISSN: 0008-4301 , 1480-3283
    RVK:
    Language: English
    Publisher: Canadian Science Publishing
    Publication Date: 2015
    detail.hit.zdb_id: 1490831-1
    SSG: 12
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  • 3
    Online Resource
    Online Resource
    Elsevier BV ; 2014
    In:  International Journal of Infectious Diseases Vol. 21 ( 2014-04), p. 185-
    In: International Journal of Infectious Diseases, Elsevier BV, Vol. 21 ( 2014-04), p. 185-
    Type of Medium: Online Resource
    ISSN: 1201-9712
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2014
    detail.hit.zdb_id: 2070533-5
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  • 4
    Online Resource
    Online Resource
    Wiley ; 2012
    In:  Medical and Veterinary Entomology Vol. 26, No. 3 ( 2012-09), p. 255-262
    In: Medical and Veterinary Entomology, Wiley, Vol. 26, No. 3 ( 2012-09), p. 255-262
    Type of Medium: Online Resource
    ISSN: 0269-283X
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2012
    detail.hit.zdb_id: 2008073-6
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  • 5
    Online Resource
    Online Resource
    Wiley ; 2012
    In:  Journal of Zoology Vol. 286, No. 4 ( 2012-04), p. 243-249
    In: Journal of Zoology, Wiley, Vol. 286, No. 4 ( 2012-04), p. 243-249
    Type of Medium: Online Resource
    ISSN: 0952-8369 , 1469-7998
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2012
    detail.hit.zdb_id: 1471807-8
    SSG: 12
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  • 6
    Online Resource
    Online Resource
    Wiley ; 2021
    In:  Journal of Zoology Vol. 314, No. 2 ( 2021-06), p. 85-95
    In: Journal of Zoology, Wiley, Vol. 314, No. 2 ( 2021-06), p. 85-95
    Abstract: African mole‐rats (family Bathyergidae) show a wide variety of social organization, from strictly solitary to highly social. Within the family, both modes of ovulation, spontaneous and induced, have been found and are thought to relate to seasonality of reproduction and opportunities for dispersal. Damaraland mole‐rats ( Fukomys damarensis ) are cooperative breeders, which breed year‐round and exhibit high reproductive skew. Reproduction is monopolized by a single female (queen) in each group, and non‐reproductive females in the presence of the queen are anovulatory. The species was previously described as being a spontaneous ovulator; however, subsequent attempts to determine the length of the oestrous cycle have failed. Therefore, we revisited this subject by studying the urinary progesterone and oestradiol profiles over a period of 7 weeks and the ovarian histology of females kept under different social conditions. The first experiment shows that average urinary progesterone concentrations of breeder females paired with a vasectomized male (full physical contact) are significantly higher than those of breeder females kept singly, non‐breeder females kept singly and non‐breeder females kept within their natal group. In the second experiment, we subjected females consecutively to different experimental conditions: full physical contact (stage 1), isolation (stage 2), non‐physical contact (stage 3) and measured their steroid hormone profiles. The females showed elevated concentrations of urinary progesterone during the phase of full physical contact and basal concentrations during the subsequent single housing phase. Correspondingly, no corpora lutea of ovulation were found in the ovaries of these females in the latter phase. During stage 3, in which females were separated from a male by wire mesh (non‐physical contact), one of three females showed elevated progesterone and oestradiol concentrations throughout the sampling period and analysis of ovarian histology revealed a corpus luteum. Together, these results support the view that Damaraland mole‐rats are induced ovulators, in which non‐coital male cues are able to induce ovulation.
    Type of Medium: Online Resource
    ISSN: 0952-8369 , 1469-7998
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2021
    detail.hit.zdb_id: 1471807-8
    SSG: 12
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  • 7
    Online Resource
    Online Resource
    Canadian Science Publishing ; 2016
    In:  Canadian Journal of Zoology Vol. 94, No. 11 ( 2016-11), p. 747-752
    In: Canadian Journal of Zoology, Canadian Science Publishing, Vol. 94, No. 11 ( 2016-11), p. 747-752
    Abstract: Many mammals use the change in day length to time physiological and behavioural activities on a seasonal basis. Particularly, mammals from temperate regions use photoperiod to regulate reproductive functions; however, information on the role of photoperiod in small mammals from the tropics and subtropics is scarce. We studied the response of the reproductive system of male eastern rock sengis (Elephantulus myurus Thomas and Schwann, 1906) from southern Africa to photoperiods of differing length. Elephantulus myurus breeds seasonally during the spring and summer months of the southern hemisphere despite its subtropical distribution. It is one of only three sengi species known to breed seasonally. Fourteen male E. myurus were subjected to either long-day (LD; 16 h light (L) : 8 h dark (D)) or short-day (SD; 8 h L : 16 h D) photoperiods and the photoperiodic effects on the testes, testosterone concentration, and body mass were examined. Testicular volume and mass, seminiferous tubule diameter, and body mass were not significantly different between LD and SD conditions. However, plasma testosterone concentration was significantly lower in males on LD photoperiods compared with SD photoperiods. Male E. myurus may not use photoperiod as a cue to control seasonal reproductive changes. Other environmental factors such as temperature, rainfall, food abundance, or social factors are possibly influencing seasonal reproduction in this species.
    Type of Medium: Online Resource
    ISSN: 0008-4301 , 1480-3283
    RVK:
    Language: English
    Publisher: Canadian Science Publishing
    Publication Date: 2016
    detail.hit.zdb_id: 1490831-1
    SSG: 12
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  • 8
    Online Resource
    Online Resource
    Canadian Science Publishing ; 2013
    In:  Canadian Journal of Zoology Vol. 91, No. 11 ( 2013-11), p. 829-836
    In: Canadian Journal of Zoology, Canadian Science Publishing, Vol. 91, No. 11 ( 2013-11), p. 829-836
    Abstract: The pattern of ovulation in mammals is generally considered to be either spontaneous or induced by copulation, with environmental and social factors playing a key role in determining the specific mode of ovulation that would maximize the reproductive potential of the species. This study aims to determine whether the Namaqua rock mouse (Micaelamys namaquensis (A. Smith, 1834)) is a spontaneous or induced ovulator. Females were divided into three treatments differing in the degree of contact with a male. Namely, seven control females had no contact with a male; a further seven separated females had only chemical, auditory, and visual contact with a male; whereas six females had intermittent periods of full contact with a vasectomized male. Ovarian size, follicular development, and plasma progesterone concentrations were compared between the three treatments. Penile morphology was also investigated. Corpora lutea were found in all three treatments and the penis was smooth without any ridges or spikes, indicating that M. namaquensis is a spontaneous ovulator. Interestingly, however, the presence of a male (physical as well as just visual and olfactory) positively affected ovarian size, ovulation, and plasma progesterone concentrations. This signifies that although M. namaquensis ovulates spontaneously, male contact significantly influences ovulation rate and ultimately reproductive success.
    Type of Medium: Online Resource
    ISSN: 0008-4301 , 1480-3283
    RVK:
    Language: English
    Publisher: Canadian Science Publishing
    Publication Date: 2013
    detail.hit.zdb_id: 1490831-1
    SSG: 12
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  • 9
    Online Resource
    Online Resource
    Canadian Science Publishing ; 2020
    In:  Canadian Journal of Zoology Vol. 98, No. 5 ( 2020-05), p. 299-305
    In: Canadian Journal of Zoology, Canadian Science Publishing, Vol. 98, No. 5 ( 2020-05), p. 299-305
    Abstract: The Mahali mole-rat (Cryptomys hottentotus mahali (Roberts, 1913)) is a social, cooperatively breeding subterranean rodent that breeds aseasonally. Only one female in a colony breeds and the remaining females are reproductively suppressed. When the opportunity arises, these non-reproductive females disperse from the natal colony to escape reproductive suppression and pair up with an unrelated male to start a new colony. This study set out to determine whether female Mahali mole-rats are induced or spontaneous ovulators once separated from the reproductive suppression of the breeding female. Fifteen separated females were subjected to three treatments: housed separately without a male (A), allowed chemical, but not physical, contact with a vasectomised male (NPC), and placed in direct contact with a vasectomised male (PC). Urine was collected from all females under each treatment every 2 days for 40 days. Only females housed in the PC treatment exhibited heightened progesterone concentrations and corpora lutea of ovulation in the ovaries. Furthermore, males possessed epidermal spines on the shaft of the penises that may be used to stimulate the cervix of the female during copulation. These findings suggest that the Mahali mole-rat is an induced ovulator.
    Type of Medium: Online Resource
    ISSN: 0008-4301 , 1480-3283
    RVK:
    Language: English
    Publisher: Canadian Science Publishing
    Publication Date: 2020
    detail.hit.zdb_id: 1490831-1
    SSG: 12
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  • 10
    Online Resource
    Online Resource
    Canadian Science Publishing ; 2021
    In:  Canadian Journal of Zoology Vol. 99, No. 9 ( 2021-09), p. 801-811
    In: Canadian Journal of Zoology, Canadian Science Publishing, Vol. 99, No. 9 ( 2021-09), p. 801-811
    Abstract: African mole-rats have provided great insight into mammalian evolution of sociality and reproductive strategy. However, some species have not received attention, and these may provide further insights into these evolutionary questions. The cooperatively breeding Mahali mole-rat (Cryptomys hottentotus mahali (Roberts, 1913)) is one such species. Body mass, reproductive-tract morphometrics, gonad histology, and plasma reproductive hormone concentrations were studied for breeding and non-breeding males and females over 1 year. This study aimed to discern if this species exhibits a seasonal or aseasonal breeding pattern and whether there is a relaxation of reproductive suppression at any point in the year in non-breeding animals. The pattern of reproductive relaxation during the wetter months is similar to other African mole-rat species. Interestingly, births and pregnant breeding females were recorded throughout the year, thus indicating an aseasonal breeding strategy, despite inhabiting a region that experiences seasonal rainfall. However, there were periods of the year favouring increased reproduction to enable an increased likelihood of offspring survival. This suggests that the Mahali mole-rat may be an opportunistic breeder possibly brought about by the benefits of living in a cooperatively breeding group and potentially moving into more arid environments that were previously unexploited by the genus Cryptomys Gray, 1864.
    Type of Medium: Online Resource
    ISSN: 0008-4301 , 1480-3283
    RVK:
    Language: English
    Publisher: Canadian Science Publishing
    Publication Date: 2021
    detail.hit.zdb_id: 1490831-1
    SSG: 12
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