Effects of photoperiod on the reproductive condition of Nile grass rats (<i>Arvicanthis niloticus</i>) from an equatorial population

Nunes, Scott; McElhinny, Teresa L.; Mahoney, Megan M.; Smale, Laura

doi:10.1046/j.1365-2028.2002.00378.x

Cited by 8 publications

(9 citation statements)

References 25 publications

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“…In contrast, day length did not affect either testes size or spermatogenesis in both S. campestris and R. pumilio, both of which seem to breed opportunistically in southern Africa (Bernard & Hall, 1995;Jackson & Bernard, 1999. In addition, Nunes et al (2002) found that photoperiod does not influence plasma testosterone concentration, testes size and seminal vesicle mass in males of the seasonally breeding Nile grass rat (Arvicanthis niloticus) from an equatorial population. Other rodents, bats and shrews, which occur near the equator, have also been found to be non-responsive to photoperiod (Rissman et al, 1987;Heideman & Bronson, 1990;O'Brien, Curlewis & Martin, 1993).…”

Section: Discussionmentioning

confidence: 73%

“…In addition, Nunes et al . () found that photoperiod does not influence plasma testosterone concentration, testes size and seminal vesicle mass in males of the seasonally breeding Nile grass rat ( Arvicanthis niloticus ) from an equatorial population. Other rodents, bats and shrews, which occur near the equator, have also been found to be non‐responsive to photoperiod (Rissman et al ., ; Heideman & Bronson, ; O'Brien, Curlewis & Martin, ).…”

Section: Discussionmentioning

confidence: 99%

“…In the tropics and subtropics, where photoperiodic changes are less pronounced, most mammals do not use photoperiod as a proximate cue (Bernard & Hall, ; Nunes et al ., ) and some even appear to have abandoned any photoperiodic time‐measuring systems (Bronson & Heideman, ). However, a few rodent species from subtropical Africa (Muteka, Chimimba & Bennett, ) and an Asian shrew species from the subtropics (Wayne & Rissman, ) have been found to be reproductively photoresponsive.…”

Section: Introductionmentioning

confidence: 99%

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Reproductive photoresponsiveness in male spiny mice from South Africa

2011

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Many seasonally breeding mammals use changes in photoperiod as a reliable cue to time reproduction. Photoperiodic timing assists an animal in predicting annual environmental changes in its habitat and therefore, enables it to accurately time reproductive events to the most favourable conditions. Changes in day length are more pronounced in the temperate regions and photoperiod is used as a cue for reproduction by most mammals above 30° latitude, however, a number of subtropical species also use this proximate factor to regulate their reproductive cycle. We investigated the reproductive photoresponsiveness of 14 male spiny mice (Acomys spinosissimus) from southern Africa to short-day (SD; 8 hrs light:16 hrs dark) and long-day (LD; 16L:8D) photoperiods. Testicular mass and volume, seminiferous tubule diameter and plasma testosterone concentrations significantly increased in animals subjected to LD and they were regressed when the males were kept under SD. Body mass of the males was not significantly affected by the photoperiodic conditions. Although male A. spinosissimus appear to use photoperiod as a proximate factor to regulate reproduction seasonally, other environmental factors, such as rainfall, food quantity and quality as well as temperature, may regulate reproduction in A. spinosissimus in concert with photoperiod. In conclusion, the present study demonstrates the significance of photoperiodic time-measuring systems in the regulation of seasonal reproduction in a sub-tropical rodent.

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Section: Discussionmentioning

confidence: 73%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Reproductive photoresponsiveness in male spiny mice from South Africa

2011

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“…In general, species that inhabit tropical climates have expanded breeding seasons compared to closely related species that live in temperate climates. Several studies have observed that short days do not inhibit reproduction in tropical rodents (Demas and Nelson, 1998;Heideman and Bronson, 1990;Nunes et al, 2002), although this outcome does not necessarily reflect an inability to detect slight changes in photoperiod in these species (Hau et al, 1998). In the tropics, photoperiod may be a less informative predictor of impending climate, so other cues may be more useful for timing reproductive activity.…”

Section: Introductionmentioning

confidence: 99%

Social and photoperiod effects on reproduction in five species of Peromyscus

Trainor

Martin

Greiwe

et al. 2006

General and Comparative Endocrinology

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At temperate latitudes, mammals and birds use changes in day length to time their reproductive activities to coincide with seasonal fluctuations in the environment. Close to the equator, however, conditions permissive of breeding do not track changes in day length as well, so other cues may be more important than photoperiod. In a variety of vertebrates, social interactions regulate breeding condition. We hypothesized that individuals of different species of Peromyscus mice found closer to the equator would respond more strongly to housing with an opposite sex conspecific than they would to photoperiod. To test this hypothesis, we compared the effects of long and short day lengths versus 8 days of pair housing with a female on reproductive tissue weights and testosterone (T) concentrations in five species of Peromyscus (P. aztecus, P. eremicus, P. maniculatus, P. melanophrys, and P. polionotus). After 13 weeks of short days (8L:16D), P. maniculatus, P. melanophrys, and P. polionotus significantly reduced relative testes mass compared to long day (16L: 8D) housed animals. Social housing, however, had no effect on tissue weights in any species. However, male P. polionotus paired with females for 8 days increased T concentrations compared to single-housed males, whereas paired P. maniculatus reduced T. These data suggest that mechanisms of photoperiodic and social regulation of reproductive function are mediated by different physiological mechanisms among closely-related species and that both phylogeny and environmental factors contribute to patterns of reproductive plasticity.

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“…where seasonal changes in day length can be perceived by this species). However, the recent study by Nunes et al. (2002) revealed that photoperiod experiments were unable to induce any reproductive changes among A. niloticus individuals from populations whose native habitat is located further south in Kenya (near 2° S latitude); suggesting that intra‐specific variation for this trait may be present within A. niloticus .…”

Section: Latitudinal Changes In Habitat Distribution Of a Niloticus mentioning

confidence: 97%

Effects of climate and local aridity on the latitudinal and habitat distribution of Arvicanthis niloticus and Arvicanthis ansorgei (Rodentia, Murinae) in Mali

Sicard

Catalan

Ag'Atteynine

et al. 2003

Journal of Biogeography

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Introduction The genus Arvicanthis (Lesson 1842) (Rodentia: Murinae), usually referred to as the unstriped grass rat, is mainly distributed in savanna and grassland habitats of Sub‐Saharan Africa. Among the four chromosomal forms of Arvicanthis recently differentiated in Western and Central Africa, the one with a diploid chromosomal number (2n) of 62 and an autosomal fundamental number (NFa) of 62 or 64 is ascribed to Arvicanthis niloticus (Demarest 1822), while the one with 2n = 62 and a NFa between 74 and 76 is referred to A. ansorgei (Thomas 1910). Despite the broad area of sympatry recently uncovered along the inner delta of the Niger river in Mali [details in Volobouev et al. (2002) Cytogenetics and Genome Research, 96, 250–260], the distribution of the two species is largely parapatric and follows the latitudinal patterns of the West‐African biogeographical domains, which are related to the latitudinal patterns of annual rainfall in this region. Here, we analyse the suggestion that the two species show specific adaptations to differences in climate aridity. Methods Karyologically screened animals were sampled in 19 localities in seasonally flooded regions located along the ‘Niger’ river in Mali and extending from 1100 to 200 mm of mean annual rainfall. The analysis of trapping success (TS) data allowed us to investigate the respective effects of climate (i.e. annual rainfall) and local (i.e. duration of the green herbaceous vegetation) aridity on the latitudinal and habitat distribution of the two species. Conclusions The broad zone of sympatry was found to correspond to a northward expansion of the recognized distribution area of A. ansorgei. TS values indicated that the two species responded very differently to climatic and local conditions of aridity. Arvicanthis ansorgei decreased in TS as regional conditions became more arid; a similar trend was also observed within regions where habitat occupancy decreased with local aridity. The higher TS observed in the most humid habitat relative to the others persisted throughout the latitudinal rainfall gradient. In contrast, TS of A. niloticus increased with latitudinal aridity. This species was present in more arid habitats than A. ansorgei from 1000 mm down to 400 mm of mean annual rainfall where a shift to the most humid habitat occurred. These opposite trends in TS distribution between species suggest that A. ansorgei is less adapted than A. niloticus to arid environments at both a regional and habitat level; thus, A. ansorgei would be able to invade dry regions only along the extensive floodplains bordering the inner delta of the ‘Niger’ river. Several biological traits that may be involved in limiting the southward distribution of A. niloticus are discussed.

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Effects of photoperiod on the reproductive condition of Nile grass rats (Arvicanthis niloticus) from an equatorial population

Cited by 8 publications

References 25 publications

Reproductive photoresponsiveness in male spiny mice from South Africa

Reproductive photoresponsiveness in male spiny mice from South Africa

Social and photoperiod effects on reproduction in five species of Peromyscus

Effects of climate and local aridity on the latitudinal and habitat distribution of Arvicanthis niloticus and Arvicanthis ansorgei (Rodentia, Murinae) in Mali

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