Abstract
BackgroundParasites can play various roles in the invasion of non-native species, but these are still understudied in marine ecosystems. This also applies to invasions from the Red Sea to the Mediterranean Sea via the Suez Canal, the so-called Lessepsian migration. In this study, we investigated the role of parasites in the invasion of the Lessepsian migrant Sphyraena chrysotaenia in the Tunisian Mediterranean Sea.MethodsWe compared metazoan parasite richness, prevalence and intensity of S. chrysotaenia (Perciformes: Sphyraenidae) with infections in its native congener Sphyraena sphyraena by sampling these fish species at seven locations along the Tunisian coast. Additionally, we reviewed the literature to identify native and invasive parasite species recorded in these two hosts.ResultsOur results suggest the loss of at least two parasite species of the invasive fish. At the same time, the Lessepsian migrant has co-introduced three parasite species during the initial migration to the Mediterranean Sea, that are assumed to originate from the Red Sea of which only one parasite species has been reported during the spread to Tunisian waters. In addition, we found that the invasive fish has acquired six parasite species that are native in the Mediterranean Sea. However, parasite richness, prevalence and intensity were overall much lower in the invasive compared to the native fish host in the Mediterranean Sea.DiscussionThese results suggest that the Lessepsian migrant may affect native fish hosts by potentially altering the dynamics of native and invasive parasite-host interactions via parasite release, parasite co-introduction and parasite acquisition. They further suggest that the lower infection levels in the invasive fish may result in a competitive advantage over native fish hosts (enemy release hypothesis). This study demonstrates that cross-species comparisons of parasite infection levels are a valuable tool to identify the different roles of parasites in the course of Lessepsian migrations.
Highlights
One of the potential explanations for the establishment and subsequent spread of invasive species in marine and other ecosystems is the enemy release hypothesis (Elton, 1958; Keane & Crawley, 2002)
After the dissections of 107 individuals of the native S. sphyraena and 148 individuals of the invasive S. chrysotaenia caught along the coast of Tunisia, ten different parasite species infecting the two fish were found
Based on samples from the Tunisian coast and additional literature data, our analyses indicate that the invasive Lessepsian migrant S. chrysotaenia lost two parasite species during its introduction to the Mediterranean Sea, but that the invasive fish co-introduced parasites from the Red Sea and acquired one generalist parasite from native fish hosts in the Mediterranean Sea (Table 2)
Summary
One of the potential explanations for the establishment and subsequent spread of invasive species in marine and other ecosystems is the enemy release hypothesis (Elton, 1958; Keane & Crawley, 2002). This parasite acquisition may have deleterious effects on naïve invasive host species (increased susceptibility hypothesis sensu Colautti et al, 2004), but may amplify native parasite population sizes, resulting in increased parasite loads in native hosts, a phenomenon which is referred to as parasite spillback (Kelly et al, 2009) While many of these mechanisms may result in a competitive advantage for invasive over native species, the magnitude of this advantage will depend on the actual difference in parasite infection levels between invasive and native hosts. These results suggest that the Lessepsian migrant may affect native fish hosts by potentially altering the dynamics of native and invasive parasite-host interactions via parasite release, parasite co-introduction and parasite acquisition. This study demonstrates that cross-species comparisons of parasite infection levels are a valuable tool to identify the different roles of parasites in the course of Lessepsian migrations
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