Helminth parasites of terrestrial and freshwater chelonians in the Neotropical region: Biogeographic distribution and new record for Phrynops geoffroanus (Schweigger, 1812) (Testudines: Chelidae) in the Brazilian semi-arid region.

The Neotropical region is considered a biodiversity hotspot for reptiles, with eight families of terrestrial and freshwater chelonians. Parasites are of great importance to aquatic ecosystems and are essential to host communities. They help understand the patterns and phylogenetic relationships of their hosts and act to control populations. A literature survey on helminth parasites of chelonians in the Neotropical region was conducted, examining the most commonly found groups of helminths, the most parasitized hosts, compiling their biogeographical and political distribution and recording the parasite fauna of Phrynops geoffroanus in the state of Paraíba, northeastern Brazil. Considering the literature from 1850 to 2024, 202 helminth taxa were recorded. The Mesoamerican dominion had the highest number of helminth taxa, and Brazil was the political unit that recorded the most helminth taxa, followed by Mexico. Nematoda was the group with the highest number of taxa and occurred in all biogeographical units, with the species Spiroxys contortus being the most commonly found, followed by Trematoda, represented by the most commonly found species, Nematophila grandis. Hosts from the Chelidae family had the highest number of helminth taxa, followed by the Kinosternidae family. The most parasitized host species were Chelonoidis denticulatus and Phrynops hilarii. For the host Phrynops geoffroanus, the first occurrence of the nematode helminth Spiroxys contortus was recorded. This is the first study to include all parasitic helminths of terrestrial and freshwater chelonians in the Neotropical region, including a new occurrence in a chelonian host in the hinterland of Paraíba, Brazil.