Effects of temperature and a manipulative parasite on the swimming behaviour of Gammarus pulex in flowing water

Abstract

Numerous freshwater acanthocephalans are able to alter the behaviour of their intermediate hosts to increase their predation risk by final hosts, thereby enhancing trophic transmission between their two hosts. Because temperature is widely expected to impact freshwater host-parasite interactions, we investigated how it can affect movements of both uninfected and Pomphorhynchus laevis-infected Gammarus pulex in an artificial stream in 5 cm/s water flow. We found that P. laevis infection of G. pulex induced both higher frequency and higher amplitude of movements along the artificial stream. Moreover, at warmer temperature (21°C), uninfected and P. laevis-infected G. pulex moved more in the artificial stream than at 15°C. In this regard, warmer temperature could then impact gammarids distribution and increase P. laevis transmission rate toward their definitive host in freshwater ecosystems. Firstly, this study provides new insights into how the key temperature factor influences gammarids species movements in the stream. Secondly, elevated temperature did not influence the intensity of P. laevis manipulation in G. pulex intermediate host. This work highlights that warmer temperature might affect the distribution and the behaviour of infected or uninfected freshwater gammarids with no direct effect on acanthocephalan trophic transmission through manipulation.

Environmental parasitology: stressor effects on aquatic parasites

“…Contrastingly, field studies from the same host parasite system found little evidence that temperature modified host-parasite interaction, and highlighted the possible difference between laboratory experiments and natural settings [61]. Likewise, studies from acanthocephalan hostparasite systems have shown that temperature changes within existing and predicted distribution ranges appear to have no impact on these behavioural changes in hosts and subsequent transmission outcomes [62,63]. Altogether, these findings emphasise the stark differences across various host-parasite associations.…”

Acanthocephalan parasites reflect ecological status of freshwater ecosystem

“…The acanthocephalan"s particular position within the food web in freshwater ecosystems requires complex biological interactions and depends on the viability of intermediate and definitive host populations (Galli et al, 1998;Hatcher et al, 2012). At their different developmental stages, acanthocephalan endoparasites are impacted either directly by their environment or indirectly through effects on their hosts (Galli et al, 2001;Hatcher et al, 2012;Fanton et al, 2021). Therefore, environmental perturbations affecting either their free-living stages or their hosts will also lead to physiological, ecological and behavioural changes for acanthocephalans (Marcogliese, 2008;Labaude et al, 2017;Sanchez-Thirion et al, 2019).…”