Predation on transmission stages reduces parasitism: sea anemones consume transmission stages of a barnacle parasite

Abstract

While parasites serve as prey, it is unclear how the spatial distribution of parasite predators provides transmission control and influences patterns of parasitism. Because many of its organisms are sessile, the rocky intertidal zone is a valuable but little used system to understand spatial patterns of parasitism and elucidate the underlying mechanisms driving these patterns. Sea anemones and barnacles are important space competitors in the rocky intertidal zone along the Pacific coast of North America. Anemones are voracious, indiscriminate predators; thus, they may intercept infectious stages of parasites before they reach a host. We investigate whether a sea anemone protects an associated barnacle from parasitism by Hemioniscus balani, an isopod parasitic castrator. At Coal Oil Point, Santa Barbara, California USA, 29% of barnacles were within 1 cm from an anemone at the surveyed tidal height. Barnacles associated with anemones had reduced parasite prevalence and higher reproductive productivity than those remote from sea anemones. In the laboratory, anemones readily consumed the transmission stage of the parasite. Hence, anemone consumption of parasite transmission stages may provide a mechanism by which community context regulates parasite prevalence at a local scale. Our results suggest predation may be an important process providing parasite transmission control.

Parasite and host biomass and reproductive output in barnacle populations in the rocky intertidal zone

“…This productivity has important implications for connectivity between populations and ecosystems. Predators often consume free-living parasites (e.g., Kaplan et al ., 2009; Orlofske et al ., 2012); in the rocky intertidal zone, in particular, intertidal anemones readily consume H. balani cryptonisci (Fong and Kuris, 2017). Parasite larvae are substantially larger than barnacle larvae and may be consumed by different species of predators, which may influence food web dynamics.…”

“…Another possibility has to do with predators on parasite infective stages. For example, anemones consume H. balani infective stages and reduce fine-scale parasite prevalence (Fong and Kuris, 2017). Thus, spatial differences among sites in levels of predation on parasites may also explain the strong variability in levels of parasitism among sites.…”

Influences of land use and ecological variables on trematode prevalence and intensity at the salt marsh‐upland ecotone

“…If we instead assume some level of causation in the correlation, G. demissa, as a filter feeder, could affect parasite infection levels directly by consuming cercaria larvae. Filter feeders can reduce the free-living infective stages of parasites as they move from one host to the next (Thieltges et al 2008, Welsh et al 2014, Fong and Kuris 2017. For example, barnacle hosts living near anemones have been known to have reduced infection burdens by their castrating isopod parasite, Hemioniscus balani (Fong and Kuris 2017).…”

“…Filter feeders can reduce the free-living infective stages of parasites as they move from one host to the next (Thieltges et al 2008, Welsh et al 2014, Fong and Kuris 2017. For example, barnacle hosts living near anemones have been known to have reduced infection burdens by their castrating isopod parasite, Hemioniscus balani (Fong and Kuris 2017). It is also possible that G. demissa shells simply provide an alternative settlement substrate for the cercariae, passively removing them from completing their life cycle (Welsh et al 2014).…”

“…Furthermore, species interactions can alter where parasites can survive and proliferate. If a predator preferentially feeds on infected prey, areas of high predator abundance can be areas of low infection prevalence (Fong and Kuris 2017, Gehman et al 2017a). For parasites with multiple hosts, the distribution of upstream hosts can influence the parasite distribution.…”