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Author |
Cameron, E.Z. |
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Title |
Facultative adjustment of mammalian sex ratios in support of the Trivers-Willard hypothesis: evidence for a mechanism |
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Journal Article |
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Year |
2004 |
Publication |
Proceedings. Biological sciences / The Royal Society |
Abbreviated Journal  |
Proc Biol Sci |
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Volume |
271 |
Issue |
1549 |
Pages |
1723-1728 |
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Keywords |
Age Factors; Animals; Body Constitution; *Evolution; Female; Glucose/metabolism/physiology; Litter Size; Male; Mammals/*physiology; *Models, Biological; Reproduction/physiology; Seasons; Sex Factors; *Sex Ratio; Time Factors |
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Abstract |
Evolutionary theory predicts that mothers of different condition should adjust the birth sex ratio of their offspring in relation to future reproductive benefits. Published studies addressing variation in mammalian sex ratios have produced surprisingly contradictory results. Explaining the source of such variation has been a challenge for sex-ratio theory, not least because no mechanism for sex-ratio adjustment is known. I conducted a meta-analysis of previous mammalian sex-ratio studies to determine if there are any overall patterns in sex-ratio variation. The contradictory nature of previous results was confirmed. However, studies that investigated indices of condition around conception show almost unanimous support for the prediction that mothers in good condition bias their litters towards sons. Recent research on the role of glucose in reproductive functioning have shown that excess glucose favours the development of male blastocysts, providing a potential mechanism for sex-ratio variation in relation to maternal condition around conception. Furthermore, many of the conflicting results from studies on sex-ratio adjustment would be explained if glucose levels in utero during early cell division contributed to the determination of offspring sex ratios. |
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Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa. ezcameron@zoology.up.ac.za |
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English |
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0962-8452 |
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PMID:15306293 |
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refbase @ user @ |
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413 |
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Author |
Thackeray, J.F. |
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Title |
Zebras from wonderwerk cave, northern Cape province, South Africa: attempts to distinguish Equus burchelli and E. quagga |
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Journal Article |
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Year |
1988 |
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South African journal of science |
Abbreviated Journal |
Suid- Afrikaanse Tydsskrif vir Wetenskap |
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84 |
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99-101 |
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Cape Province; Teeth; Statistical analysis; Equidae; Hippomorpha; South Africa; Southern Africa; Perissodactyla; Mammalia; Vertebrata |
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0038-2353 |
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from Professor Hans Klingels Equine Reference List |
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yes |
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1644 |
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Author |
Creel, S. |
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Title |
Social dominance and stress hormones |
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Journal Article |
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Year |
2001 |
Publication |
Trends in Ecology & Evolution |
Abbreviated Journal |
Trends. Ecol. Evol |
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16 |
Issue |
9 |
Pages |
491-497 |
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Keywords |
Dominance; rank; stress; glucocorticoids; cooperative breeding; sociality; behavioural endocrinology; mammals |
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In most cooperatively breeding birds and mammals, reproductive rates are lower for social subordinates than for dominants, and it is common for reproduction in subordinates to be completely suppressed. Early research conducted in captivity showed that losing fights can increase glucocorticoid (GC) secretion, a general response to stress. Because GCs can suppress reproduction, it has been widely argued that chronic stress might underlie reproductive suppression of social subordinates in cooperative breeders. Contradicting this hypothesis, recent studies of cooperative breeders in the wild show that dominant individuals have elevated GCs more often than do subordinates. The findings that elevated GCs can be a consequence of subordination or a cost of dominance complicate the conventional view of social stress, with broad ramifications for the evolution of dominance and reproductive suppression. |
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Equine Behaviour @ team @ |
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4072 |
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Author |
Wilson, D.A.; Stevenson, R.J. |
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Title |
The fundamental role of memory in olfactory perception |
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Journal Article |
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Year |
2003 |
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Trends in Neurosciences |
Abbreviated Journal |
Trends. Neurosci. |
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26 |
Issue |
5 |
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243-247 |
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Keywords |
olfactory perception mammals |
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Current emphasis on odorant physiochemical features as the basis for perception largely ignores the synthetic and experience-dependent nature of olfaction. Olfaction is synthetic, as mammals have only limited ability to identify elements within even simple odor mixtures. Furthermore, olfaction is experience-bound, as exposure alone can significantly affect the extent to which stimuli can be discriminated. We propose that early analytical processing of odors is inaccessible at the behavioral level and that all odors are initially encoded as `objects' in the piriform cortex. Moreover, we suggest that odor perception is wholly dependent on the integrity of this memory system and that its loss severely impairs normal perception. |
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refbase @ user @ |
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795 |
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Author |
Sukhomlinov, B.F.; Korobov, V.N.; Gonchar, M.V.; Datsiuk, L.A.; Korzhev, V.A. |
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Title |
[Comparative analysis of the peroxidase activity of myoglobins in mammals] |
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Journal Article |
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Year |
1987 |
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Zhurnal Evoliutsionnoi Biokhimii i Fiziologii |
Abbreviated Journal |
Zh Evol Biokhim Fiziol |
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23 |
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1 |
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37-41 |
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Amino Acid Sequence; Animals; Ecology; *Evolution; Kinetics; Mammals/*metabolism; Myoglobin/*metabolism; Peroxidases/*metabolism |
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Studies have been made on the peroxidase activity of metmyoglobins in animals from various ecological groups--the horse Equus caballus, cattle Bos taurus, beaver Castor fiber, otter Lutra lutra, mink Mustela vison and dog Canis familiaris. It was found that the level of this activity in diving animals depends on the duration of their diving, whereas in terrestrial species--on the strength of muscular contraction. |
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Russian |
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Sravnitel'nyi analiz peroksidaznoi aktivnosti mioglobinov u mlekopitaiushchikh |
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0044-4529 |
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PMID:3564776 |
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Equine Behaviour @ team @ |
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2681 |
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Author |
Wang, L.Y. |
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Title |
Host preference of mosquito vectors of Japanese encephalitis |
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Journal Article |
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Year |
1975 |
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Zhonghua Minguo wei Sheng wu xue za zhi = Chinese Journal of Microbiology |
Abbreviated Journal |
Zhonghua Min Guo Wei Sheng Wu Xue Za Zhi |
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8 |
Issue |
4 |
Pages |
274-279 |
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Keywords |
Animals; *Behavior, Animal; Birds/blood; *Culex; Ecology; Encephalitis, Japanese/*transmission; *Feeding Behavior; Female; Humans; *Insect Vectors; Mammals/blood; Species Specificity; Taiwan |
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The host preference of 4 Culex mosquito species collected in Miaoli and Pingtung counties, Taiwan was studied by capillary precipitin method. Antisera to alum-precipitated sera of man, bovine, swine, rabbit, horse, dog, cat, mouse, chicken, duck, and pigeon were produced in rabbits and reacted with 758 mosquito blood meals among which reactions to one or more antisera. Culex annulus and Culex tritaeniorhynchus summorosus showed a great avidity for pig, and Culex fuscocephala for bovine. Culex pipiens fatigans was ornithophilic. None of 110 C. t. summorosus and 2.4% of 223 C. annulus had fed on man. Among 66 samples of C.p. fatigans tested 10.3% had fed on man, while none of 359 C. fuscocephala did. It seems that the latter does not act as a primary vector of Japanese encephalitis. |
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0009-4587 |
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PMID:181218 |
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Equine Behaviour @ team @ |
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2702 |
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