Abstract
Escape from parasites in their native range is one of many mechanisms that can contribute to the success of an invasive species. Gnathiid isopods are blood-feeding ectoparasites that infest a wide range of fish hosts, mostly in coral reef habitats. They are ecologically similar to terrestrial ticks, with the ability to transmit blood-borne parasites and cause damage or even death to heavily infected hosts. Therefore, being highly resistant or highly susceptible to gnathiids can have significant fitness consequences for reef-associated fishes. Indo-Pacific red lionfish (Pterois volitans) have invaded coastal habitats of the western tropical and subtropical Atlantic and Caribbean regions. We assessed the susceptibility of red lionfish to parasitic gnathiid isopods in both their native Pacific and introduced Atlantic ranges via experimental field studies during which lionfish and other, ecologically-similar reef fishes were caged and exposed to gnathiid infestation on shallow coral reefs. Lionfish in both ranges had very few gnathiids when compared with other species, suggesting that lionfish are not highly susceptible to infestation by generalist ectoparasitic gnathiids. While this pattern implies that release from gnathiid infestation is unlikely to contribute to the success of lionfish as invaders, it does suggest that in environments with high gnathiid densities, lionfish may have an advantage over species that are more susceptible to gnathiids. Also, because lionfish are not completely resistant to gnathiids, our results suggest that lionfish could possibly have transported blood parasites between their native Pacific and invaded Atlantic ranges.
Highlights
Parasites make up about 40% of the earth’s biodiversity and parasitism constitutes the most common type of ecological interaction [1]
At two invaded localities, most red lionfish did not become infested with gnathiids, whereas most individuals of the native comparison species did
Even when the experiment was repeated at invaded sites with much higher abundances of gnathiids (Virgin Islands), the results were similar; a higher proportion of lionfish became infested with at least one gnathiid, but densities were far lower than on native grunts
Summary
Parasites make up about 40% of the earth’s biodiversity and parasitism constitutes the most common type of ecological interaction [1]. Because of their effects on host population dynamics, parasites directly or indirectly influence the dynamics and structure of ecological communities [2]. The effects of host-specialists are easiest to predict and have received the most attention as components of ‘‘enemy release’’ [4], [5]: introduced species likely leave behind specialist parasites from their native range and are likely avoided, at least initially, by specialist parasites in the introduced range due to a lack of shared evolutionary history. Some other studies of wild-caught hosts revealed that non-native species tend to have fewer generalist parasites (external crustaceans and internal helminths) than their sympatric, native counterparts [12], [13]
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