Artemia franciscana is an invasive crustacean expanding its range in hypersaline wetlands in the Mediterranean region and replacing native Artemia parthenogenetica and Artemia salina. Native brine shrimps are known as intermediate hosts of cestodes; infected individuals exhibit changes in their behaviour and appearance, thus facilitating the parasite transmission to the avian hosts by predation. To assess whether invasive brine shrimps participate in the cestode life cycles to the same extent as the native species, we examined the natural infections in seven populations of Artemia spp. along the southern coast of Spain and Portugal: three populations of each A. franciscana and A. parthenogenetica and one population of A. salina. Ten cestode species were found in A. parthenogenetica, while only six were recorded in each of A. salina and A. franciscana. The overall infection was consistently higher in native than in invasive populations. For a particular cestode species, the prevalence or abundance was significantly higher in a native population for 54 pairwise comparisons and only higher for an invasive population for 4 pairwise comparisons. These results suggest that cestodes may influence competitive interactions between native and invasive brine shrimps, thus partly explaining the invasive success of A. franciscana.

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Although the red colour of brine shrimps has previously been supposed to be associated with cestode parasitism, no evidence has been provided that red and transparent brine shrimps differ in their role for cestode circulation. We compared the cestode infections in 100 red and 100 transparent Artemia parthenogenetica collected from the Odiel salt pans in Spain. Seven cestode species were recorded in red, and only four of them were recorded in transparent brine shrimps. The red brine shrimps were more infected with cysticercoids than transparent individuals (prevalence, 87 vs 21%; mean intensity, 1.56 vs 1.00; mean abundance, 1.35 vs 0.21). Three cestode species (Flamingolepis liguloides, Anomotaenia tringae and Confluaria podicipina) had significantly higher prevalence and mean abundance in red brine shrimps. These results suggest that red brine shrimps have a more important role for the circulation of avian cestodes than transparent individuals of the same population.