Roper et al data on mite transmission between slugs

Transmission between hosts is crucial to the growth, development and
reproduction of many parasites. As a consequence, parasites are under
selection to maximise transmission success and exhibit many behavioural
and morphological adaptations that allow detection of, and movement
between, hosts. However, transmission success is not determined by
parasites alone, but is also shaped by host behaviours. Often, host
behaviours function to minimise the risk of exposure to parasites; in some
cases, however, host behaviours may be manipulated by parasites to
increase transmission success. In this study, we investigated transmission
of the ectoparasitic mite Riccardoella oudemansi between slug (Limacus
maculatus) hosts, considering the role of both host and parasite behaviour
in determining transmission success. Host-host transmission occurred when
slugs were in physical contact, but that mites were also capable of moving
across the substrate to locate new hosts, a process facilitated by mucus
trails. We found no strong evidence that slugs avoid parasitised
conspecifics, or that mites manipulate slug behaviour to increase
transmission. Finally, mites showed a preference for the mucus of
parasitised slugs, but did not discriminate between mucus from their own
host versus another parasitised slug. A general preference for mucus from
parasitised slugs is likely to be important in encouraging mites to remain
in close contact with their host and may also facilitate host-switching
and outbreeding. We encourage further study of parasitism by Riccardoella
in limacid slugs, where cross-species variation in host social behaviour
may drive differences in the rate and success of parasite transmission
across slug species.