Hawlena Hadas, Abramsky Zvika, Krasnov Boris R
Department of Life Sciences and Ramon Science Center, Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Beer-Sheva, 84105, Israel.
Oecologia. 2007 Dec;154(3):601-9. doi: 10.1007/s00442-007-0851-7. Epub 2007 Sep 9.
Mechanisms that cause nonrandom patterns of parasite distribution among host individuals may influence the population and evolutionary dynamics of both parasites and hosts, but are still poorly understood. We studied whether survival, reproduction, and behavioral responses of fleas (Xenopsylla conformis) changed with the age of their rodent hosts (Meriones crassus), experimentally disentangling two possible mechanisms: (a) differential survival and/or fitness reward of parasites due to host age, and (b) active parasite choice of a host of a particular age. To explore the first mechanism, we raised fleas on rodents of two age groups and assessed flea survival as well as the quantity and quality of their offspring. To explore the second mechanism, three groups of fleas that differed in their previous feeding experience (no experience, experience on juvenile or experience on adult rodents) were given an opportunity to choose between juvenile and adult rodents in a Y-maze. Fleas raised on juvenile rodents had higher survival and had more offspring that emerged earlier than fleas raised on adults. However, fleas did not show any innate preference for juvenile rodents, nor were they able to learn to choose them. In contrast to our predictions, based on a single previous exposure, fleas learned to choose adult rodents. The results suggest that two mechanisms-differential survival and fitness reward of fleas, and associative learning by them-affect patterns of flea distribution between juvenile and adult rodents. The former increases whereas the latter reduces flea densities on juvenile rodents. The ability of fleas to learn to choose adult but not juvenile hosts may be due to: (a) a stronger stimulus from adults, (b) a higher profitability of adults in terms of predictability and abundance, or (c) the evolutionary importance of recognizing adult but not juvenile hosts as representatives of the species.
导致寄生虫在宿主个体间呈非随机分布模式的机制，可能会影响寄生虫和宿主的种群及进化动态，但目前仍知之甚少。我们研究了跳蚤（Xenopsylla conformis）的生存、繁殖和行为反应是否会随着其啮齿动物宿主（肥尾心颅跳鼠，Meriones crassus）的年龄而变化，通过实验区分了两种可能的机制：（a）由于宿主年龄导致寄生虫的生存差异和/或适应性回报，以及（b）寄生虫对特定年龄宿主的主动选择。为了探究第一种机制，我们在两个年龄组的啮齿动物上饲养跳蚤，并评估跳蚤的生存情况以及它们后代的数量和质量。为了探究第二种机制，我们将三组先前取食经历不同（无经历、在幼年啮齿动物上取食经历、在成年啮齿动物上取食经历）的跳蚤置于Y型迷宫中，让它们有机会在幼年和成年啮齿动物之间进行选择。在幼年啮齿动物上饲养的跳蚤比在成年啮齿动物上饲养的跳蚤具有更高的生存率，且有更多更早羽化的后代。然而，跳蚤对幼年啮齿动物并没有任何先天偏好，也无法学会选择它们。与我们基于单次先前接触的预测相反，跳蚤学会了选择成年啮齿动物。结果表明，两种机制——跳蚤的生存差异和适应性回报，以及它们的联想学习——影响了跳蚤在幼年和成年啮齿动物之间的分布模式。前者增加而后者降低了幼年啮齿动物上的跳蚤密度。跳蚤学会选择成年而非幼年宿主的能力可能是由于：（a）来自成年宿主的更强刺激，（b）成年宿主在可预测性和数量方面更高的收益性，或者（c）将成年而非幼年宿主识别为物种代表的进化重要性。
