Seasonal changes in host phenotype manipulation by an acanthocephalan: time to be transmitted?

Abstract

Many complex life cycle parasites exhibit seasonal transmission between hosts. Expression of parasite traits related to transmission, such as the manipulation of host phenotype, may peak in seasons when transmission is optimal. The acanthocephalan Acanthocephalus lucii is primarily transmitted to its fish definitive host in spring. We assessed whether the parasitic alteration of 2 traits (hiding behaviour and coloration) in the isopod intermediate host was more pronounced at this time of year. Refuge use by infected isopods was lower, relative to uninfected isopods, in spring than in summer or fall. Infected isopods had darker abdomens than uninfected isopods, but this difference did not vary between seasons. The level of host alteration was unaffected by exposing isopods to different light and temperature regimes. In a group of infected isopods kept at 4 xC, refuge use decreased from November to May, indicating that reduced hiding in spring develops during winter. Keeping isopods at 16 xC instead of 4 xC resulted in higher mortality but not accelerated changes in host behaviour. Our results suggest that changes in host and/or parasite age, not environmental conditions, underlie the seasonal alteration of host behaviour, but further work is necessary to determine if this is an adaptive parasite strategy to be transmitted in a particular season.

Increased temperature has no consequence for behavioral manipulation despite effects on both partners in the interaction between a crustacean host and a manipulative parasite

“…A seasonal effect of manipulation was also documented in gammarids infected by acanthocephalan parasites 71 , although the mechanisms explaining such seasonality were not identified. Our study supports the hypothesis made by Benesh et al 67 who suggested that seasonal changes in manipulation might not be caused by proximal abiotic conditions. In other studies, only light properties were shown to affect manipulation 68,69 , while other factors such as the quantity of resources available did not affect manipulation either 45 .…”

Host manipulation in the face of environmental changes: Ecological consequences

“…Several manipulative parasites also present seasonal variations, not only in their prevalence, but also in the intensity of their manipulation. For instance, some acanthocephalan parasites induce a stronger change in refuge use by their isopod hosts during spring, compared to summer or fall ( Benesh et al., 2009a ). Benesh et al.…”

“…For instance, some acanthocephalan parasites induce a stronger change in refuge use by their isopod hosts during spring, compared to summer or fall ( Benesh et al., 2009a ). Benesh et al. (2009a) suggested that seasonal variations in isopod behavioral alterations could result from a manipulation strategy adjusted to seasonal variation in the diet of definitive hosts.…”

Impact of olfactory non-host predator cues on aggregation behaviour and activity in Polymorphus minutus infected Gammarus pulex

“…Bakker et al, 1997;Maynard et al, 1998;Médoc et al, 2006;Kaldonski et al, 2008;Benesh et al, 2009), where the amphipods serve as intermediate hosts that have to be ingested by birds or fishes, the parasite's final hosts (Crompton & Nickol, 1985). Fish parasites of the genus Pomphorhynchus are known to manipulate the photophobic behaviour (Bethel & Holmes, 1973;Kennedy et al, 1978;Bakker et al, 1997), the response to predator fish cues (Baldauf et al, 2007;Perrot-Minnot et al, 2007) as well as the activity of their amphipod intermediate hosts, and make them more conspicuous as the yellow-orange cystacanths are clearly visible through their cuticle (Bakker et al, 1997).…”