Parasite-Induced Changes in Behavior and Color Make Gammarus Pulex More Prone to Fish Predation

Abstract

The acanthocephalan parasite Pomphorhynchus laevis is transmitted by crustaceans such as Gammarus pulex to its paratenic or final hosts, fish. The conspicuous orangeyellow parasite is visible through the transparent cuticle of G. pulex. Infected gammarids are significantly less photophobic than uninfected ones. When hungry three-spined sticklebacks (Gasterosteus aculeatus), one of the hosts of this parasite, were offered equal numbers of uninfected and infected prey, G. pulex infected with P. laevis were eaten significantly more often. We tested experimentally whether parasite color and parasite-induced changes in host behavior affected the predation rate of G. pulex. Color effects were tested with uninfected G. pulex by painting an orange spot on their cuticle that simulated infection. Behavioral effects were tested with infected G. pulex by covering the place through which the orange parasite was visible with inconspicuous brown paint. We showed for the first time that both parasite color and changed intermediate host behavior promote the transmission of P. laevis to its next host. The evolution of orange parasite color, and why sticklebacks do not avoid infected prey, are discussed.

Does the acanthocephalan parasite Polymorphus minutus modify the energy reserves and antitoxic defences of its intermediate host Gammarus roeseli?

“…Our study underlined higher glycogen contents in P. minutusinfected G. roeseli as compared to uninfected ones, whatever the gender. We can hypothesize that the higher glycogen content in infected gammarids could be due to their immobility, since P. minutus-infected gammarids are known to stay at the water surface where they become more vulnerable to final host predation (Bakker et al 1997;Bauer et al 2000Bauer et al , 2005Cézilly and Perrot-Minnot, 2005;Médoc et al 2006).…”

From population-level effects to individual response: modelling temperature dependence in Gammarus pulex

“…At the same time, G. pulex may behave as a predator and as a cannibal (MacNeil et al, 1997;Kelly et al, 2002). It is a model organism for the study of several topics, for instance parasitology and sexual selection (Bollache and Cézilly, 2004;Dahl and Greenberg, 1996), understanding longitudinal drift (Elliott, 2002) and predation (Bakker et al, 1997). The life span of G. pulex varies between 1 and 2years (Sutcliffe et al, 1981).…”

“…In field monitoring, food shortage could be thought of as being more severe because of competition with other shredders (F4). Additionally, a temperature-dependent increase in the food demand of predators, for instance by fish (Bakker et al, 1997), could amplify the temperature response of mortality of their prey. Moreover, cannibalism (MacNeil et al, 1997) may vary depending on temperature and food availability.…”

Parasite manipulation of brain monoamines in California killifish ( Fundulus parvipinnis ) by the trematode Euhaplorchis californiensis

“…Typically, altered behaviours appear to increase parasite fitness by enhancing the likelihood of transmission between hosts in the parasite's life cycle (Holmes & Bethel 1972;Barber et al 2000;Combes 2001;Moore 2002;Kuris 2003; reviews in Thomas et al 2005). Predator hosts often consume a higher proportion of infected prey-whose manipulated behaviours render them easier to catch-a phenomenon termed parasite-increased trophic transmission (PITT ;Carney 1969;Holmes & Bethel 1972;Brassard et al 1982;Hoogenboom & Dijkstra 1987;Lafferty 1992;Lafferty & Morris 1996;Bakker et al 1997;Thomas & Poulin 1998;Lafferty 1999;McCurdy et al 1999;Berdoy et al 2000;Knudsen et al 2001). From both a proximate and an ultimate perspective, it remains of considerable interest whether the behavioural changes of the infected prey result from the side effects of general debilitation, orwhether the parasites actively target the host's neuroendocrine systems (reviewed in Thomas et al 2005).…”