Ultimate mechanisms of age-biased flea parasitism |
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Authors: | Hadas Hawlena Zvika Abramsky Boris R Krasnov |
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Institution: | (1) Department of Life Sciences and Ramon Science Center, Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Beer-Sheva, 84105, Israel;(2) Present address: Department of Biology, Indiana University, Bloomington, IN 47405, USA;(3) Department of Life Sciences, Ben-Gurion University of the Negev, Beer-Sheva, 84105, Israel;(4) Mitrani Department of Desert Ecology, Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede-Boqer Campus, 84490 Midreshet Ben-Gurion, Israel;(5) Ramon Science Center, P.O. Box 194, Mizpe Ramon, 80600, Israel |
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Abstract: | 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. |
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Keywords: | Host choice Learning Distribution among host individuals Fitness reward Rodents |
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