Reproduction is an energy-demanding activity in mammalian females, with increased energy requirements during pregnancy and, especially, during lactation. To better understand the interactions between parasitism and host reproduction, we investigated feeding and reproductive performance of fleas (Xenopsylla ramesis) parasitizing non-reproducing, pregnant or lactating gerbilline rodents (Meriones crassus). Based on energetic considerations, we predicted that feeding and reproductive performance of fleas would be lowest on non-breeding females, moderate on pregnant females and highest on lactating females. We estimated feeding performance of the fleas via absolute and mass-specific bloodmeal size and reproductive performance via egg production and latency to peak oviposition. Host reproductive status had no effect on either absolute or mass-specific bloodmeal size or the day of peak oviposition, but significantly affected the daily number of eggs produced by a female flea. Surprisingly, and contrary to our predictions, egg production of fleas fed on pregnant rodents was significantly lower than that of fleas on non-reproducing and lactating rodents, while no difference in egg production between fleas feeding on non-reproducing and lactating hosts was found. Our results suggest that differences in parasite reproduction when feeding on hosts of different reproductive status are not associated with the different energy requirements of the hosts at non-breeding, pregnancy and lactation but rather with variation in hormonal and/or immune status during these periods.
KEY WORDS: Ectoparasites, Egg production, Lactation, Pregnancy
INTRODUCTIONReproduction is one of the most energy-demanding activities experienced by mammalian females. To achieve high reproductive output (e.g. production of a large number of offspring), females not only increase the level of resource acquisition (Lee, 1987;Randolph et al., 1995;Speakman, 2008) but also often use their own energy reserves (Degen et al., 2002). Allocation of energy to reproduction is, however, hindered by other energetically demanding activities that occur concomitantly (Kam and Degen, 1993). Parasites hijack resources belonging to a host and use these resources for their own maintenance and reproduction. A host, in turn, faces energy costs of parasitism including not only direct loss of energy taken over by parasites but also costs of immunological and/or behavioural anti-parasitic defences. Although anti-parasitic defences are highly demanding energetically (Sheldon and Verhulst, 1996;Lochmiller and Deerenberg, 2000;Zuk and Stoehr, 2002), their costs can be compensated for by reduced feeding and/or reproductive performance of parasites (Fielden et al., 1992), which, in turn, decreases the direct cost of parasitism.
RESEARCH ARTICLEThe cost of parasitism is critical in reproducing hosts and is paid by either the parents (reduced mass, survival, future reproductive performance) (Brown et al., 1995;Richner and Tripet, 1999; Fitze et al., 2004;Neuhaus, 2003) or the of...