Abstract
Parasite manipulation of intermediate hosts evolves to increase parasite trophic transmission to final hosts, yet counter selection should act on the final host to reduce infection risk and costs. However, determining who wins this arms race and to what extent is challenging. Here, for the first time, comparative functional response analysis quantified final host consumption patterns with respect to intermediate host parasite status. Experiments used two evolutionarily experienced fish hosts and two naive hosts, and their amphipod intermediate hosts of the acanthocephalan parasite Pomphorhynchus tereticollis. The two experienced fish consumed significantly fewer infected than non-infected prey, with lower attack rates and higher handling times towards the former. Conversely, the two naive fish consumed similar numbers of infected and non-infected prey at most densities, with similar attack rates and handling times towards both. Thus, evolutionarily experienced final hosts can reduce their infection risks and costs via reduced intermediate host consumption, with this not apparent in naive hosts.
Highlights
Final hosts and their parasites are involved in an evolutionary arms race, whereby trophically transmitted parasites manipulate their intermediate hosts to increase transmission rates, but with final hosts presumably experiencing selection to minimize the risks of infection and subsequent fitness costs [1,2]
The Ca. auratus comparative functional responses (CFRs) curves indicated differences between prey types were minimal at low prey densities (e.g. mean consumption rate at 32 items (+95% confidence limits): 24.7 + 3.0/23.0 + 4.2 n.h21) and only at the highest prey densities did consumption rates of infected amphipods decrease versus non-infected
The evolutionary arms race between trophically transmitted parasites and their final hosts involves the interaction of the parasites manipulating the behaviours of their intermediate hosts versus potential final hosts minimizing their infection risk and fitness costs [1,2,3,4,5]
Summary
Final hosts and their parasites are involved in an evolutionary arms race, whereby trophically transmitted parasites manipulate their intermediate hosts to increase transmission rates, but with final hosts presumably experiencing selection to minimize the risks of infection and subsequent fitness costs [1,2]. As selection is likely to favour hosts reducing their costs of infection [4], final host populations could evolve behaviours that reduce their ingestion of prey infected with tropically transmitted parasites [4,5]. The development of these adaptive behaviours might be influenced by the host’s previous experience of the parasite, with experienced hosts likely to elicit stronger anti-parasite responses than naive hosts due to the presence/absence of shared eco-evolutionary histories [6]. We propose that comparative functional responses (CFRs), which compare prey consumption rate as functions of prey density [7,8,9], can assess
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