Lutermann Heike, Medger Katarina, Horak Ivan G
Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Private Bag X20, Hatfield, 0028, South Africa.
Naturwissenschaften. 2012 Feb;99(2):103-10. doi: 10.1007/s00114-011-0874-0. Epub 2011 Dec 15.
The distribution of parasites is often characterised by substantial aggregation with a small proportion of hosts harbouring the majority of parasites. This pattern can be generated by abiotic and biotic factors that affect hosts and determine host exposure and susceptibility to parasites. Climate factors can change a host's investment in life-history traits (e.g. growth, reproduction) generating temporal patterns of parasite aggregation. Similarly, host age may affect such investment. Furthermore, sex-biased parasitism is common among vertebrates and has been linked to sexual dimorphism in morphology, behaviour and physiology. Studies exploring sex-biased parasitism have been almost exclusively conducted on polygynous species where dimorphic traits are often correlated. We investigated the effects of season and life-history traits on tick loads of the monogamous eastern rock sengi (Elephantulus myurus). We found larger tick burdens during the non-breeding season possibly as a result of energetic constraints and/or climate effects on the tick. Reproductive investment resulted in increased larval abundance for females but not males and may be linked to sex-specific life-history strategies. The costs of reproduction could also explain the observed age effect with yearling individuals harbouring lower larval burdens than adults. Although adult males had the greatest larval tick loads, host sex appears to play a minor role in generating the observed parasite heterogeneities. Our study suggests that reproductive investment plays a major role for parasite patterns in the study species.
寄生虫的分布通常具有高度聚集的特征，少数宿主携带了大部分寄生虫。这种模式可能由影响宿主并决定宿主接触寄生虫和易感性的非生物和生物因素所导致。气候因素可以改变宿主在生活史特征（如生长、繁殖）上的投入，从而产生寄生虫聚集的时间模式。同样，宿主年龄也可能影响这种投入。此外，性别偏向的寄生现象在脊椎动物中很常见，并且与形态、行为和生理上的性别二态性有关。探索性别偏向寄生现象的研究几乎都只在多配偶物种中进行，在这些物种中，二态性特征往往相互关联。我们研究了季节和生活史特征对一夫一妻制的东部岩象鼩（象鼩属 象鼩）蜱虫负荷的影响。我们发现非繁殖季节的蜱虫负担更重，这可能是由于能量限制和/或气候对蜱虫的影响。生殖投入导致雌性幼虫数量增加，而雄性则没有，这可能与特定性别的生活史策略有关。繁殖成本也可以解释观察到的年龄效应，一岁个体的幼虫负担低于成年个体。尽管成年雄性的幼虫蜱虫负荷最大，但宿主性别在产生观察到的寄生虫异质性方面似乎只起次要作用。我们的研究表明，生殖投入在该研究物种的寄生虫模式中起主要作用。
