Short-term elevation of glucocorticoids(GCs)is one of the major physiological mechanisms by which vertebrates cope with challenging environmental or social factors(stressors).However,when exposure to stressors occurs ...Short-term elevation of glucocorticoids(GCs)is one of the major physiological mechanisms by which vertebrates cope with challenging environmental or social factors(stressors).However,when exposure to stressors occurs repeatedly or over a prolonged period of time,animals may experience chronic elevation of GCs,which reduces the immune response efficiency and can lead to higher intensity of parasitic infection.Here,we used invasive gray squirrels Sciurus carolinensis in troduced in Norther n Italy and their 2 most prevale nt gastrointesti nal parasites,the n ematode Strongyloides robustus and coccidia of the genus Eimeria,as a model to investigate relati on ships among macroparasite infection and concentrations of fecal glucocorticoid metabolites(FGMs),an integrated measure of circulating GCs.Our results revealed an association of FGMs with infection by St.robustus,but not with coccidia.Individuals with higher FGMs appear to be responsible for the greatest St.robustus egg shedding within gray squirrel populations,thus possibly acting as superspreaders.However,FGMs were negatively associated with adult St.robustus,suggesting that the abundance of adults of this nematode species does not induce elevation in FGMs,but is only affected by it through immun e-mediated effects on its fecun dity.Fin ally,the relati on ship betwee n St.robustus(both eggs and adult parasites)and FGMs was not linear,suggesting that only high levels of physiological stress in fluence parasite inf ection.Our fin dings highlight that the direction and magnitude of the stress-infection relationship may depend not only on the specific hostparasite system,but also on the different life stages of the same parasite.展开更多
文摘动物的活动节律是动物对时间资源利用的重要体现,同域分布物种间对时间利用的差异是物种共存机制之一。为了研究喀斯特石山生境中赤腹松鼠Callosciurus erythraeus和红颊长吻松鼠Dremomys rufigenis的活动节律,进一步探讨这两者的时间生态位分化,2015年9月—2016年10月利用红外相机技术在广西弄岗国家级自然保护区对这2种松鼠的活动节律进行研究,并基于Shannon-Wiener多样性指数和核密度估计法(kernel density estimation)分别计算它们的时间生态位宽度指数与活动节律的重叠程度。结果显示:赤腹松鼠和红颊长吻松鼠的时间生态位宽度分别为0.8451和0.8036,2种松鼠都倾向于昼行性。不同时段获得的独立有效照片数量有显著的变化(赤腹松鼠:t=5.12,df=23,P<0.001;红颊长吻松鼠:t=4.60,df=23,P<0.001)。此外,2种松鼠间的独立有效照片数有显著差异(Z=-2.21,P=0.03)。2种松鼠活动节律曲线的重叠度Δ4为0.8392,日活动节律曲线差异显著(P<0.001),这说明它们在不同时段的活动强度有差异。这种活动节律的差异性,可能是它们减缓竞争,达到共存的生态策略之一。
基金Thanks to Zainab Almusawi and Teera Losch for helping in laboratory analysis,Candice Gagnaison,Laure Vanlauwe,and Mattia Panzeri for assistance with the fieldwork.We are grateful to the private land owners for access to their estates.Three anonymous reviewers provided constructive comments that helped us to improve the article.
文摘Short-term elevation of glucocorticoids(GCs)is one of the major physiological mechanisms by which vertebrates cope with challenging environmental or social factors(stressors).However,when exposure to stressors occurs repeatedly or over a prolonged period of time,animals may experience chronic elevation of GCs,which reduces the immune response efficiency and can lead to higher intensity of parasitic infection.Here,we used invasive gray squirrels Sciurus carolinensis in troduced in Norther n Italy and their 2 most prevale nt gastrointesti nal parasites,the n ematode Strongyloides robustus and coccidia of the genus Eimeria,as a model to investigate relati on ships among macroparasite infection and concentrations of fecal glucocorticoid metabolites(FGMs),an integrated measure of circulating GCs.Our results revealed an association of FGMs with infection by St.robustus,but not with coccidia.Individuals with higher FGMs appear to be responsible for the greatest St.robustus egg shedding within gray squirrel populations,thus possibly acting as superspreaders.However,FGMs were negatively associated with adult St.robustus,suggesting that the abundance of adults of this nematode species does not induce elevation in FGMs,but is only affected by it through immun e-mediated effects on its fecun dity.Fin ally,the relati on ship betwee n St.robustus(both eggs and adult parasites)and FGMs was not linear,suggesting that only high levels of physiological stress in fluence parasite inf ection.Our fin dings highlight that the direction and magnitude of the stress-infection relationship may depend not only on the specific hostparasite system,but also on the different life stages of the same parasite.