Review of the Acanthocephalans of Turtles: Diversity, Distribution, and Turtle Host–Parasite Associations

Turtle acanthocephalans, within the genus Neoechinorhynchus, are a relatively understudied group of organisms, and most of these reports are scattered throughout the literature. This has resulted in a relatively poor understanding of host–parasite associations for turtle Neoechinorhynchus species. Therefore, the goal of this review was to assess the literature for acanthocephalan reports in turtle hosts to better understand host–parasite trends relating to turtle acanthocephalans. Additionally, a meta-analysis of prevalence and intensity was derived from the available data. A thorough assessment was conducted from peer-reviewed publications, theses, online museum databases, and novel data from turtle surveys throughout Oklahoma and acquired worms from collaborators across the United States. A total of 73 unique reports (peer-reviewed publications, theses, and nonpublished museum voucher records) were identified in this review. Results from this review indicate that turtle acanthocephalans have been reported from 26 states in the United States and 4 states in Mexico. Acanthocephalan species diversity appeared highest in the southeastern and southwestern regions of the United States, with few species reported in Mexico and no reports from Canada. Among all reports of turtle acanthocephalans, the overall meta-prevalence was 58%, and the meta-intensity was 110 worms per turtle. A total of 21 species of turtles have been identified as potential hosts for acanthocephalans, making up 27% of all North American turtle species. The most common turtle family reported was Emydidae, with Trachemys scripta containing the most acanthocephalan species (9 of the 10 currently described species). Lastly, 4 acanthocephalan species, Neoechinorhynchus chrysemydis, Neoechinorhynchus emydis, Neoechinorhynchus emyditoides, and Neoechinorhynchus pseudemydis, appeared the most successful in terms of distribution and turtle host range. Overall, these results suggest that turtle acanthocephalans are common freshwater turtle parasites in the United States and contain a relatively low degree of host specificity. There are likely additional turtle species for which acanthocephalans have yet to be reported and new species to be described. This review provides a novel database of turtle acanthocephalan reports and helps fill in several knowledge gaps regarding turtle–acanthocephalan biogeography, ecology, and host specificity. Finally, suggestions are provided to guide future researchers in testing novel hypotheses that will likely promote turtle acanthocephalan research.