Morph‐dependent nematode infection and its association with host movement in the land snail <i>Cepaea nemoralis</i> (Mollusca, Gastropoda)

Abstract Host behaviour can be influenced by parasitic risk and infection through a variety of direct indirect mechanisms. We expect individuals expressing different phenotypes to also differ in the ways their is altered parasites. used land snail Cepaea nemoralis , species with various shell colour morphs differing physiology, as model study link between parasite response individual variation. analysed metazoan abundance its relation (movement food intake) snails from three (from light unbanded darker five‐banded) two neighbouring populations contrasting environments. Snails were parasitized mites, trematodes, nematodes, rarest most frequent. confirm that terrestrial gastropods defend against trapping nematodes shell. show encapsulated shells uncover past infections even when population currently nematode‐free, possibly due seasonality. present new observations suggesting not only but mites might shells. Infection levels varied morphs, harbouring fewer nematodes. Behaviour was linked nematode, trematode infection. Individuals higher nematode load ate less, irrespective morph population. The most‐infected (unbanded snails) showed reduced activity nematode‐infected compared one nematode‐free at sampling time. As result, parasites may cancel previously described behavioural differences morphs. discuss possible mechanisms explaining morph‐dependent responses parasites, how an unseen force shaping C. variation space conclude ecological consequences link, mediated colour, thermal immune responses.