51
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Sedelaar JM, Dalrymple SS, Isaacs JT. Of mice and men--warning: intact versus castrated adult male mice as xenograft hosts are equivalent to hypogonadal versus abiraterone treated aging human males, respectively. Prostate 2013; 73:1316-25. [PMID: 23775398 PMCID: PMC4009979 DOI: 10.1002/pros.22677] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/11/2013] [Accepted: 03/26/2013] [Indexed: 11/07/2022]
Abstract
BACKGROUND Immune deficient male mice bearing human prostate cancer xenografts are used to evaluate therapeutic response to novel androgen ablation approaches and the results compared to surgical castration based upon assumption that testosterone microenvironment in intact and castrated adult male mice mimics eugonadal and castrated aging adult human males. METHODS To test these assumptions, serum total testosterone (TT) and free testosterone (FT) were determined longitudinally in groups (n > 20) of intact versus castrated adult male nude, NOG, and immune competent C57BL/6 mice. RESULTS In adult male mice, TT and FT varies by 30- to 100-fold within the same animal providing a microenvironment that is only equivalent to hypogonadal, not eugonadal, adult human males (TT is 1.7 ± 1.2 ng/ml [5.8 ± 4.1 nM] in nude and 2.5 ± 1.3 ng/ml [8.7 ± 4.4 nM] in NOG mice versus >4.2 ng/ml [14.7 nM] in eugonadal humans). This was confirmed based upon enhanced growth of androgen dependent human prostate cancer xenografts inoculated into mice supplemented with exogenous testosterone to elevate and chronically maintain serum TT at a level (5 ng/ml [18 nM]) equivalent to a 50-year-old eugonadal human male. In castrated mice, TT and FT range from 2 to 20 pg/ml (7-70 pM) and <0.8 pg/ml (<2.6 pM), respectively, which is equivalent to castrate resistant prostate cancer (CRPC) patients treated with abiraterone. This was confirmed based upon the inability of another CYP17A1 inhibitor, ketoconazole, to inhibit the growth of CRPC xenografts in castrated mice. CONCLUSIONS Adult male mice supplemented with testosterone mimic eugonadal human males, while unsupplemented animals mimic standard androgen ablation and castrated animals mimic abiraterone treated patients. These studies confirm what is claimed in Robert Burns' poem "To a Mouse" that "The best laid schemes of mice and men/often go awry.".
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Affiliation(s)
- J.P. Michiel Sedelaar
- Department of Oncology, Sidney Kimmel Comprehensive Cancer Center, School of Medicine, The Johns Hopkins University, Baltimore, Maryland
| | - Susan S. Dalrymple
- Department of Oncology, Sidney Kimmel Comprehensive Cancer Center, School of Medicine, The Johns Hopkins University, Baltimore, Maryland
- Correspondence to: Sidney Kimmel Comprehensive Cancer Center, Bunting and Blaustein Building (CRB-1), 1650 Orleans Street, Baltimore, MD 21287.
| | - John T. Isaacs
- Department of Oncology, Sidney Kimmel Comprehensive Cancer Center, School of Medicine, The Johns Hopkins University, Baltimore, Maryland
- Department of Urology, James Buchanan Brady Urological Institute, School of Medicine, The Johns Hopkins University, Baltimore, Maryland
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Woodruff JA, Lacey EA, Bentley GE, Kriegsfeld LJ. Effects of social environment on baseline glucocorticoid levels in a communally breeding rodent, the colonial tuco-tuco (Ctenomys sociabilis). Horm Behav 2013; 64:566-72. [PMID: 23928366 DOI: 10.1016/j.yhbeh.2013.07.008] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/09/2013] [Revised: 07/28/2013] [Accepted: 07/29/2013] [Indexed: 11/30/2022]
Abstract
The social environment in which an animal lives can profoundly impact its physiology, including glucocorticoid (GC) responses to external stressors. In social, group-living species, individuals may face stressors arising from regular interactions with conspecifics as well as those associated with basic life history needs such as acquiring food or shelter. To explore the relative contributions of these two types of stressors on glucocorticoid physiology in a communally breeding mammal, we characterized baseline GC levels in female colonial tuco-tucos (Ctenomys sociabilis), which are subterranean rodents endemic to southwestern Argentina. Long-term field studies have revealed that while about half of all yearling female C. sociabilis live and breed alone, the remainder live and breed within their natal group. We assessed the effects of this intraspecific variation in social environment on GC physiology by comparing concentrations of baseline fecal corticosterone metabolite (fCM) for (1) lone and group-living yearling females in a free-living population of C. sociabilis and (2) captive yearling female C. sociabilis that had been experimentally assigned to live alone or with conspecifics. In both cases, lone females displayed significantly higher mean baseline fCM concentrations. Data from free-living animals indicated that this outcome arose from differences in circadian patterns of GC production. fCM concentrations for group-living animals declined in the afternoon while fCM in lone individuals did not. These findings suggest that for C. sociabilis, stressors associated with basic life history functions present greater challenges than those arising from interactions with conspecifics. Our study is one of the first to examine GC levels in a plural-breeding mammal in which the effects of group-living are not confounded by differences in reproductive or dominance status, thereby generating important insights into the endocrine consequences of group-living.
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Affiliation(s)
- Julie A Woodruff
- Museum of Vertebrate Zoology, University of California, Berkeley, CA 94720, USA; Department of Integrative Biology, University of California, Berkeley, CA 94720, USA.
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Schoepf I, Schradin C. Endocrinology of sociality: comparisons between sociable and solitary individuals within the same population of African striped mice. Horm Behav 2013; 64:89-94. [PMID: 23648775 DOI: 10.1016/j.yhbeh.2013.04.011] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/22/2012] [Revised: 04/20/2013] [Accepted: 04/25/2013] [Indexed: 10/26/2022]
Abstract
The social organization of species ranges from solitary-living to complex social groups. While the evolutionary reasons of group-living are well studied, the physiological mechanisms underlying alternative social systems are poorly understood. By studying group-living and solitary individuals of the same species, we can determine hormonal correlates of sociality without the problem of confounding phylogenetic factors. The African striped mouse (Rhabdomys pumilio) is a socially flexible species, which can be solitary or alternatively form complex family groups, depending on population density and the extent of reproductive competition. We predicted group-living striped mice to show signs of reproductive suppression and social stress, resulting in higher corticosterone but lower testosterone levels when compared to solitary-living individuals. To determine whether differences in social organization correlated with hormonal differences, we collected blood samples from free-living striped mice during four breeding seasons when we experimentally induced solitary-living in philopatric individuals by locally reducing population density. Striped mice that were group-living did not change their corticosterone or estosterone levels during the study, indicating that there was no temporal effect during the breeding season. Striped mice of both sexes had significantly lower corticosterone levels after switching from group- to solitary-living. Solitary males - but not solitary females - had higher testosterone levels than group-living conspecifics. Our results suggest that group-living results in physiological stress and can induce reproductive suppression, at least in philopatric males. The switch to solitary-living may thus be a tactic to avoid reproductive competition within groups, and is associated with decreased stress hormone levels and onset of independent reproduction.
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Affiliation(s)
- Ivana Schoepf
- Department of Animal Behaviour, Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Zurich, Switzerland.
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54
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Higham JP, Heistermann M, Maestripieri D. The endocrinology of male rhesus macaque social and reproductive status: a test of the challenge and social stress hypotheses. Behav Ecol Sociobiol 2013; 67:19-30. [PMID: 24634561 PMCID: PMC3950204 DOI: 10.1007/s00265-012-1420-6] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Social status primarily determines male mammalian reproductive success, and hypotheses on the endocrinology of dominance have stimulated unprecedented investigation of its costs and benefits. Under the challenge hypothesis, male testosterone levels rise according to competitive need, while the social stress hypothesis predicts glucocorticoid (GC) rises in high ranking individuals during social unrest. Periods of social instability in group-living primates, primarily in baboons, provide evidence for both hypotheses, but data on social instability in seasonally-breeding species with marked social despotism but lower reproductive skew are lacking. We tested these hypotheses in seasonally-breeding rhesus macaques on Cayo Santiago, Puerto Rico. We documented male fecal GC and androgen levels over a 10 month period in relation to rank, age, natal status and group tenure length, including during a socially unstable period in which coalitions of lower-ranked males attacked higher-ranked males. Androgen but not GC levels rose during the mating season; older males had lower birth season levels but underwent a greater inter-season rise than younger males. Neither endocrine measure was related to rank except during social instability, when higher ranked individuals had higher and more variable levels of both. High ranking male targets had the highest GC levels of all males when targeted, and also had high and variable GC and androgen levels across the instability period. Our results provide evidence for both the challenge and social stress hypotheses.
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Affiliation(s)
- James P Higham
- Institute for Mind and Biology, University of Chicago, 940 East 57 Street, Chicago, IL 60637, USA ; Department of Anthropology, New York University, 25 Waverly Place, New York, NY 10003, USA
| | - Michael Heistermann
- Reproductive Biology Unit, German Primate Centre, Kellnerweg 4, 37077, Göttingen, Germany
| | - Dario Maestripieri
- Institute for Mind and Biology, University of Chicago, 940 East 57 Street, Chicago, IL 60637, USA
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55
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Schradin C, Kenkel W, Krackow S, Carter CS. Staying put or leaving home: endocrine, neuroendocrine and behavioral consequences in male African striped mice. Horm Behav 2013; 63:136-43. [PMID: 23079108 DOI: 10.1016/j.yhbeh.2012.10.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/12/2012] [Revised: 10/08/2012] [Accepted: 10/09/2012] [Indexed: 11/25/2022]
Abstract
Social flexibility occurs when individuals of both sexes can change their social and reproductive tactics, which in turn can influence the social system of an entire population. However, little is known regarding the extent to which individuals of socially flexible species vary in their social behavior and in the underlying physiological mechanisms that support different social tactics. The present study in African striped mice modeled in captivity three male tactics described from the field: (a) philopatric males remaining in the family; (b) solitary roamers; or (c) group-living breeding males. Sixteen pairs and their offspring were kept in captivity, while one male offspring from the family remained as singly housed after he reached 21 days of age. Differences in behavior, morphology, hormone and neuropeptide levels were tested, and physiological measurements were correlated with behavioral measurements. In standardized arena experiments group-living males (philopatrics and breeders) were significantly more aggressive than singly housed males, in agreement with previous data suggesting that group-living, but not roaming males, are territorial. Philopatric males showed signs of reproductive suppression, small testes, lower testosterone and higher corticosterone levels than their singly housed brothers. Higher levels of arginine vasopressin (AVP) were measured in the PVN and BNST of singly housed males compared to group-living males. Based on these findings we hypothesize that roamers are physiologically primed, and capable, if the opportunity to mate arises, to release AVP, form social bonds and become territorial, thus quickly adopting the tactic as breeding male which would yield a higher reproductive success.
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Affiliation(s)
- Carsten Schradin
- Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland.
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56
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Differences in social behaviour between group-living and solitary African striped mice, Rhabdomys pumilio. Anim Behav 2012. [DOI: 10.1016/j.anbehav.2012.08.019] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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57
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Vera F, Zenuto RR, Antenucci CD. Seasonal variations in plasma cortisol, testosterone, progesterone and leukocyte profiles in a wild population of tuco-tucos. J Zool (1987) 2012. [DOI: 10.1111/j.1469-7998.2012.00967.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Bukovetzky E, Fares F, Schwimmer H, Haim A. Reproductive and metabolic responses of desert adapted common spiny male mice (Acomys cahirinus) to vasopressin treatment. Comp Biochem Physiol A Mol Integr Physiol 2012; 162:349-56. [DOI: 10.1016/j.cbpa.2012.04.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2011] [Revised: 04/08/2012] [Accepted: 04/09/2012] [Indexed: 10/28/2022]
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Raynaud J, Müller K, Schradin C. Experimental increase of testosterone levels in free-ranging juvenile male African striped mice (Rhabdomys pumilio) induces physiological, morphological, and behavioral changes. Gen Comp Endocrinol 2012; 178:108-15. [PMID: 22565164 DOI: 10.1016/j.ygcen.2012.04.028] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/29/2011] [Revised: 04/23/2012] [Accepted: 04/26/2012] [Indexed: 10/28/2022]
Abstract
Testosterone influences sexual differentiation in early development, and activates sexual maturation and sex-related behavior in males during puberty. Testosterone can also influence the expression of male alternative reproductive tactics, by either organizational effects (fixed tactics) or by activational effects (plastic tactics). However, the roles of testosterone in sexual maturation and at the same time the expression of alternative reproductive tactics have been little investigated experimentally, and studies of free-ranging mammals are lacking. We conducted a field experiment in free-ranging juvenile African striped mice (Rhabdomys pumilio), a species with alternative reproductive tactics. Juvenile male striped mice reaching puberty can remain in their family as philopatric group-living males with low testosterone levels, or they can disperse and become solitary living roamers with much higher testosterone levels. We tested whether experimentally increased testosterone levels in non-scrotal juvenile males induces puberty and leads to the expression of the roaming tactic. Testosterone-treated males received the hormone for 15days by silastic implants which were empty in control-treated males. When compared to control-treated males, testosterone-treated males had higher testosterone levels, lower corticosterone levels, and became scrotal with descended testes. Testosterone-treated males also had larger testes, larger epididymides, and showed indication of spermatogenesis. Testosterone-treated males did not become solitary-living roamers, but had larger home ranges than control males. We conclude that testosterone can induce sexual maturation and causes juvenile males to increase their home ranges, maybe to search for dispersal opportunities.
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Affiliation(s)
- Julien Raynaud
- Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, Zurich, Switzerland.
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60
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Schradin C, Eder S, Müller K. Differential investment into testes and sperm production in alternative male reproductive tactics of the African striped mouse (Rhabdomys pumilio). Horm Behav 2012; 61:686-95. [PMID: 22445749 DOI: 10.1016/j.yhbeh.2012.03.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/10/2011] [Revised: 03/06/2012] [Accepted: 03/07/2012] [Indexed: 11/25/2022]
Abstract
Males that follow alternative reproductive tactics might differ in their investment into testis development and sperm production. The resource-allocation hypothesis predicts that males following a sneaker tactic should invest more into sperm production than dominant territorial males which should invest more into mate guarding. This hypothesis is supported by studies in species where individual males cannot switch between tactics (fixed tactics). Here we present the first data for a species where males can switch between tactics (plastic tactics). We studied African striped mice (Rhabdomys pumilio) in captivity, mimicking three tactics observed in the field: philopatric group-living males, singly-housed males representing roaming males, and group-living breeding males. We measured quantitative and qualitative reproductive traits, as well as serum and testis hormone concentrations. We found no support for the resource-allocation hypothesis, since breeding and singly-housed males invested similarly in testes and sperm. However, philopatric males had significantly smaller testes and epididymides, lower sperm counts, lower testosterone and higher corticosterone levels than males of the two other tactics. Philopatric males did not reach a larger body mass than singly-housed males with well developed reproductive traits, indicating that they did not trade investment in sperm production against growth. Interestingly, testis testosterone concentrations of philopatric males did not differ from those of other males. Our data suggest that philopatric males are reproductively suppressed by the breeding male, but might be ready to increase their serum testosterone levels when social and environmental conditions allow for this physiological switch accompanying the behavioral switch between tactics.
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Affiliation(s)
- Carsten Schradin
- Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstr. 190, 8057 Zurich, Switzerland.
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61
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Schradin C, Yuen CH. Hormone levels of male African striped mice change as they switch between alternative reproductive tactics. Horm Behav 2011; 60:676-80. [PMID: 21968215 DOI: 10.1016/j.yhbeh.2011.09.002] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/21/2011] [Revised: 08/22/2011] [Accepted: 09/06/2011] [Indexed: 10/17/2022]
Abstract
Alternative reproductive tactics occur when individuals of the same species follow alternative ways to maximize reproductive success. Often younger and smaller males follow tactics that result in lower fitness than that of dominant larger males. The relative plasticity hypothesis predicts that hormone levels change as males change tactics, but direct tests of this hypothesis are missing. It has been demonstrated in a number of studies that males following different tactics also differ in hormone levels (unpaired data), but not that individual males change their hormone levels as they change tactic (paired data). We compared hormone levels in the same individuals before and after they changed their tactic, using field samples collected over a period of 6 years. We studied male striped mice (Rhabdomys pumilio) following three alternative reproductive tactics: 1. alloparental philopatric males; 2. solitary roaming males, and 3. group-living dominant breeders. Testosterone levels increased and corticosterone levels decreased when philopatric males became roamers or breeders. The increase in testosterone levels tended to be higher in philopatric males that became roamers than in philopatric males that became breeders. Testosterone levels decreased when roamers became breeders. Prolactin levels increased when males of any other tactic became breeders. Thus, males significantly changed their hormone profiles as they changed tactics. These results are in agreement with the hypothesis that changes in hormone levels are associated with the switch from one alternative reproductive tactic to another.
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Affiliation(s)
- Carsten Schradin
- Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland.
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62
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Vera F, Zenuto RR, Antenucci CD, Busso JM, Marín RH. Validation of a radioimmunoassay for measuring testosterone concentrations in plasma samples of the subterranean rodent Ctenomys talarum: outstandingly elevated levels in the wild and the effect of captivity. ACTA ACUST UNITED AC 2011; 315:572-83. [DOI: 10.1002/jez.707] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2011] [Revised: 08/01/2011] [Accepted: 08/03/2011] [Indexed: 12/22/2022]
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63
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SCHRADIN CARSTEN, LINDHOLM ANNAK, JOHANNESEN JES, SCHOEPF IVANA, YUEN CHIHANG, KÖNIG BARBARA, PILLAY NEVILLE. Social flexibility and social evolution in mammals: a case study of the African striped mouse (Rhabdomys pumilio). Mol Ecol 2011; 21:541-53. [DOI: 10.1111/j.1365-294x.2011.05256.x] [Citation(s) in RCA: 110] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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64
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Vera F, Antenucci CD, Zenuto RR. Cortisol and corticosterone exhibit different seasonal variation and responses to acute stress and captivity in tuco-tucos (Ctenomys talarum). Gen Comp Endocrinol 2011; 170:550-7. [PMID: 21095193 DOI: 10.1016/j.ygcen.2010.11.012] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/18/2009] [Revised: 11/08/2010] [Accepted: 11/17/2010] [Indexed: 10/18/2022]
Abstract
In this work we aimed to evaluate variations in plasma glucocorticoids (GCs, cortisol and corticosterone) levels throughout an annual cycle in free-living male tuco-tucos (Ctenomys talarum) and compare their responses to acute and chronic stressors (trapping, manipulation, immobilization, confinement in a novel environment, transference to captivity). In addition, we used leukocyte profiles to allow discrimination between basal and stress-induced seasonal changes in GC concentrations. Our results showed that cortisol and corticosterone are differently affected by environmental stimuli in C. talarum. Both hormones showed different patterns of variation in the field and responses to captivity. Moreover, only cortisol was responsive to acute stressors. Leukocyte profiles indicated that animals were unstressed in the field and therefore, that we were able to measure basal, stress-independent, fluctuations in GC levels. GC concentrations were low in comparison to values frequently reported for other mammals. Our results suggest differentiated physiological roles for cortisol and corticosterone in our study species and further emphasize the complexity of GC physiology in wild mammals.
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Affiliation(s)
- Federico Vera
- Laboratorio de Ecofisiología, Departamento de Biología, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata, CC 1245, Mar del Plata 7600, Argentina.
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65
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Spatial variation in gender-biased parasitism: host-related, parasite-related and environment-related effects. Parasitology 2010; 137:1527-36. [PMID: 20550754 DOI: 10.1017/s0031182010000454] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The gender-biased pattern of parasite infestation has been shown to be a complicated phenomenon that cannot be explained by a single mechanism but rather involves several different mechanisms. We asked what are the factors that affect the manifestation and extent of gender-biased parasitism and studied the relationship between parasite-related (mean abundance, mean species richness and total species richness of all parasites), host-related (rodent density and proportion of reproductive males and females both separately and together) and environment-related (mean daily maximal and minimal temperatures, rainfall and relative humidity) factors and the magnitude of gender-biased infestation of a South African rodent Rhabdomys pumilio by ixodid ticks, gamasid mites, lice and fleas. We found that spatial variation in gender differences in parasite infestation was affected by parasite-, host- and environment-related factors, although the set of factors affecting gender differences in infestation differed among higher taxa of ectoparasites. Gender differences in infestation by fleas and lice were affected mainly by parasite-related factors, whereas gender differences in infestation by ticks and, in part, by mites were affected mainly by host-related and environmental factors. In addition, spatial variation in most measures of gender difference in mite infestation remained unexplained.
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66
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Wilson DR, McDonald PG, Evans CS. Mechanisms of Mate Investment in the Polygamous Fowl, Gallus gallus. Ethology 2010. [DOI: 10.1111/j.1439-0310.2010.01800.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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67
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Lynn SE, Prince LE, Phillips MM. A single exposure to an acute stressor has lasting consequences for the hypothalamo-pituitary-adrenal response to stress in free-living birds. Gen Comp Endocrinol 2010; 165:337-44. [PMID: 19682993 DOI: 10.1016/j.ygcen.2009.07.018] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/15/2009] [Revised: 07/29/2009] [Accepted: 07/31/2009] [Indexed: 10/20/2022]
Abstract
In vertebrates, activation of the hypothalamo-pituitary-adrenal (HPA) axis in response to unpredictable events results in elevated glucocorticoid secretion. Repeated exposure to stressors alters subsequent glucocorticoid secretion, either by inducing chronic stress or as a result of habituation. However, most studies of repeated stress focus on the impacts of multiple and frequent exposures to acute stressors, and few have been carried out in free-living animals. We investigated whether a single exposure to a novel stressor was sufficient to produce long-lasting alterations in HPA function in free-living eastern bluebirds (Sialia sialis). We subjected adult females to a capture/restraint protocol in which we collected serial blood samples over an hour of restraint to be analyzed for corticosterone. We administered this protocol to three groups of females during the nestling phase of their first and/or second brood of the season: Repeaters (sampled during brood 1 and brood 2), Naïve-Brood 1 (sampled only during brood 1), and Naïve-Brood 2 (sampled only during brood 2). Repeaters had attenuated corticosterone responses to the second restraint bout compared to the first, and in brood 2, Repeaters had lower responses than Naïve-Brood 2 females. However, Naïve-Brood 1 and Naïve-Brood 2 birds did not differ in their responses to restraint. Thus, as little as one prior experience with an acute stressor was sufficient to alter subsequent HPA responsiveness, and this effect was not due to a natural change in HPA responsiveness as the breeding season progressed. These data may have important implications for understanding how acute stressors can alter a free-living animal's ability to cope in the face of subsequent stressors, and for longitudinal field studies in which individuals are repeatedly sampled for glucocorticoid responsiveness.
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Affiliation(s)
- Sharon E Lynn
- The College of Wooster, Department of Biology, Wooster, OH 44691, USA.
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68
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Schradin C, Scantlebury M, Pillay N, König B. Testosterone levels in dominant sociable males are lower than in solitary roamers: physiological differences between three male reproductive tactics in a sociably flexible mammal. Am Nat 2010; 173:376-88. [PMID: 19199528 DOI: 10.1086/596535] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
The relative plasticity hypothesis predicts that alternative tactics are associated with changes in steroid hormone levels. In species with alternative male reproductive tactics, the highest androgen levels have usually been reported in dominant males. However, in sociable species, dominant males show amicable behaviors to gain access to females, which might conflict with high testosterone levels. We compared testosterone, corticosterone, and resting metabolic rate in male striped mice (Rhabdomys pumilio) following a conditional strategy with three different reproductive tactics: (i) philopatric group-living males, (ii) solitary-living roamers, (iii) dominant but sociable group-living territorial breeders. Philopatrics had the lowest testosterone but highest corticosterone levels, suggesting that they make the best of a bad job. Dominant territorial breeders had lower testosterone levels than roamers, which have a lower competitive status. Roamers had the highest testosterone levels, which might promote risky behavior, such as invading territories defended by territorial males. Roamers also had lower resting metabolic rates than either type of group-living males. Our results suggest that dominant males' testosterone levels reflect a trade-off between low testosterone amicable behavior and high testosterone dominance behavior.
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Affiliation(s)
- Carsten Schradin
- Institute of Zoology, University of Zurich, Winterthurerstrasse 190, Zurich, Switzerland.
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69
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Schradin C, Schmohl G, Rödel HG, Schoepf I, Treffler SM, Brenner J, Bleeker M, Schubert M, König B, Pillay N. Female home range size is regulated by resource distribution and intraspecific competition: a long-term field study. Anim Behav 2010. [DOI: 10.1016/j.anbehav.2009.10.027] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Finkler H, Terkel J. Cortisol levels and aggression in neutered and intact free-roaming female cats living in urban social groups. Physiol Behav 2009; 99:343-7. [PMID: 19954748 DOI: 10.1016/j.physbeh.2009.11.014] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2009] [Revised: 10/22/2009] [Accepted: 11/23/2009] [Indexed: 11/17/2022]
Abstract
Free-roaming domestic cats in urban areas often live in defined social groups, and the breeding females in these groups tend to form structures of a matrilineal nature. In recent years, resulting from the growing populations of free-roaming cats in many cities worldwide, these cats are being managed using the Trap-Neuter-Return (TNR) method. The aims of this study were to explore the hypotheses that (a) neutering reduces aggression in the females living in such social groups; and (b) if such reduction does occur, that it might be accompanied by a reduction in cortisol levels. The study was conducted on eight cat feeding groups in residential neighbourhoods in Tel Aviv, Israel. The municipal veterinary department offers TNR services upon request. Cats are collected from the feeding group and returned to their original group after neutering. We found that neutered females showed reduced aggressiveness as well as reduced cortisol levels compared to the intact females. In addition, those intact females that displayed more aggression had higher cortisol levels compared to the less aggressive intact females. Based on the results of this study it is possible to suggest for the first time a possible relationship between cortisol levels and aggression in free-roaming female domestic cats. This study is an initial step in assessing the long-term effects of Trap-Neuter-Return (TNR) on the welfare of the individual cat. If cortisol levels in female cats are reduced after neutering, partly as a result of reduced social and reproductive pressures (as expressed by lower aggression of the neutered females), it is possible that TNR has an added beneficial role in cat welfare in addition to that of control of population size.
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Affiliation(s)
- H Finkler
- Zoology Department, George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv, Tel Aviv 69978, Israel.
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Mileva V, Fitzpatrick J, Marsh‐Rollo S, Gilmour K, Wood C, Balshine S. The Stress Response of the Highly Social African CichlidNeolamprologus pulcher. Physiol Biochem Zool 2009; 82:720-9. [DOI: 10.1086/605937] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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72
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Schradin C, Schneider C, Yuen CH. Age at puberty in male African striped mice: the impact of food, population density and the presence of the father. Funct Ecol 2009. [DOI: 10.1111/j.1365-2435.2009.01569.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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73
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Beldomenico PM, Telfer S, Lukomski L, Gebert S, Bennett M, Begon M. Host condition and individual risk of cowpox virus infection in natural animal populations: cause or effect? Epidemiol Infect 2009; 137:1295-301. [PMID: 19144246 PMCID: PMC2952828 DOI: 10.1017/s0950268808001866] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Recent studies have provided evidence that endemic pathogens may affect dynamics in animals. However, such studies have not typically considered that infected individuals might have a preceding underlying poor condition. We examined whether individuals in poor condition are more likely to become infected by an endemic pathogen, using as a system the dynamics of cowpox virus in field voles. With data from monthly sampled vole populations, a nested case-control study evaluated whether susceptible individuals with poorer condition had higher probabilities of contracting cowpox. The influence of condition was found to be considerable, especially for males. At times when a susceptible male with good body condition had a relatively low probability of becoming infected, a susceptible male with poor body condition was twice as likely to contract cowpox; if this male was also anaemic, the chances were almost quadrupled. We discuss the care needed when interpreting the findings of wildlife disease studies.
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Matthee S, Krasnov BR. Searching for generality in the patterns of parasite abundance and distribution: Ectoparasites of a South African rodent, Rhabdomys pumilio. Int J Parasitol 2009; 39:781-8. [DOI: 10.1016/j.ijpara.2008.12.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2008] [Revised: 12/12/2008] [Accepted: 12/15/2008] [Indexed: 10/21/2022]
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75
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Nováková M, Palme R, Kutalová H, Janský L, Frynta D. The effects of sex, age and commensal way of life on levels of fecal glucocorticoid metabolites in spiny mice (Acomys cahirinus). Physiol Behav 2008; 95:187-93. [DOI: 10.1016/j.physbeh.2008.05.017] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2008] [Revised: 05/20/2008] [Accepted: 05/28/2008] [Indexed: 10/22/2022]
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