生命是短暂的，特别对那些成熟快、死亡早的动物来说，更是如此。所以，没有理由不抓紧时间生活每一天。美国科学家近日研究发现，生活速度快（寿命较短）的小鼠更愿意用发烧而不是发育完全的免疫响应来应对受到的感染，这样它们就不必打断日常生活以从疾病中康复。相关论文10月29日在线发表于《功能生态学》（Functional Ecology）上。
动物对付病菌的方法除了使用免疫系统外，还有其它多种方法，比如提高身体温度、减少进食、嗜睡、减少性活动和进攻行为等。但是这些方法都会带来副作用，比如减少性活动会损害健康，而身体温度每提高1摄氏度就要消耗身体多于10%的能量。而关于不同动物不同选择的内在原因，科学家所知甚少。
在最新的研究中，美国南佛罗里达大学的进化生态学家Lynn Martin和同事向美国、加拿大和墨西哥的5种亲缘关系很近的小鼠注射了脂多糖（lipopolysaccharide），使小鼠身体产生感染症状。研究人员随后监测了这些小鼠24小时之内的身体温度和行为模式。
结果发现，快速生活的白足鼠（Peromyscus leucopus）和鹿鼠（P. maniculatus）很快就产生了发烧症状；较慢速生活的阿兹台克鼠（P. Aztec）和高原鼠（P. melanophrys）只有一点点发烧症状或者完全没有；而生活节奏更慢的荒漠鼠（P. californicus）体温不仅没有提高，反而有所下降。
Martin认为，这其中的原因在于，发烧能够帮助清除病原体，效果较快。但是发烧同样会对身体组织造成长期的损害，这会缩短寿命。对于寿命较短的动物来说，发烧是更好的选择，因为如果寿命是短暂的，那么就不会在乎长期的损害，也不会愿意花上3到4周的时间来从疾病中康复。而对于寿命较长的动物来说，它们更愿意依赖效果慢但副作用也小的抗体来对付感染。这很好地解释了，为什么慢速生活的小鼠在实验中表现出疾病行为，而快速生活的小鼠很少表现或不表现。
美国加州大学戴维斯分校的动物学家Kirk Klasing说，之前有许多科学家猜测，动物不同的生活策略会导致选择不同的方式来抵御病原体，而这次的研究第一次给出了明确的证据。（科学网 杰克·梅/编译）
原始出处:
OnlineEarly Articles
To cite this article: Lynn B. Martin II, Zachary M. Weil, Randy J. Nelson
Fever and sickness behaviour vary among congeneric rodents
Functional Ecology (OnlineEarly Articles).
doi:10.1111/j.1365-2435.2007.01347.x
Fever and sickness behaviour vary among congeneric rodents
Lynn B. Martin II**Correspondence author. Division of Integrative Biology, University of South Florida, 4202 East Fowler Avenue, Tampa, FL 33620, USA. E-mail: lmartin@cas.usf.edu, Zachary M. Weil and Randy J. Nelson
Departments of Psychology, Neuroscience, and Evolution, Ecology, and Organismal Biology, The Ohio State University, Columbus, OH 43210, USA
*Correspondence author. Division of Integrative Biology, University of South Florida, 4202 East Fowler Avenue, Tampa, FL 33620, USA. E-mail: lmartin@cas.usf.edu
Key-words : acute phase response, immune, lipopolysaccharide, Peromyscus, trade-off
Functional Ecology (2007) doi: 10.1111/j.1365-2435.2007.01347.x
Functional Ecology (2007) xx, 000–000
1. Fever and sickness behaviour are immune defences that most organisms engage to control bacterial and viral infections. Although generally beneficial, these defences can be energetically expensive, which may lead to variation within and among species. Here, we asked whether fever and sickness behaviour differ among five species of mice in the genus, Peromyscus.
2. This comparison was motivated by our previous discovery of extensive, but systematic, immunological variation among many of these same rodent species. Some species were adept at controlling gram-negative bacteria whereas others were proficient at generating antibodies; no species was strongly capable of both. Such discrete variation suggested a continuum of immune defence strategies. We therefore predicted that variation in fever and sickness behaviour would mirror variation in bacterial killing capacity, as these defences are mediated by some of the same molecular pathways.
3. To test this hypothesis, we characterized responses to lipopolysaccharide (LPS), a component of gram-negative bacteria that activates febrile responses without causing infection. Peromyscus species that showed little sickness behaviour post-LPS engaged fever; species that engaged sickness behaviour, however, either did not mount fevers or became hypothermic post-LPS. As predicted, species that were adept at killing bacteria in vitro mounted the largest fevers; species that were not as proficient at killing bacteria did not engage fever.
4. These results further indicate a continuum of immunological strategies among Peromyscus species, which we expect applies to other taxa. We propose a few possible reasons for why species occupy specific points along an immune continuum; life-history orientation appears the most viable alternative at present.
