Host-Sharing Dynamics at Play: First Record of Spiroxys contortus in Kinosternon scorpioides from Brazilian Amazon

The genus Spiroxys Schneider, 1866 comprises species that commonly parasitize chelonians of the suborder Cryptodira found in the Holarctic and Asian regions. Spiroxys contortus (Rudolphi, 1819) was described as parasitizing a freshwater turtle of the suborder Cryptodira in the Palearctic region and is 1 of the most widely recorded species of the genus worldwide, with records even extending to Brazil. Thus, this study aims to report the first record of S. contortus in Kinosternon scorpioides (Linnaeus, 1766), a cryptodiran freshwater turtle of the family Kinosternidae, from 3 municipalities in the Brazilian Amazon. Nematodes were collected from the turtles' stomachs and identified with light microscopy. We identified several intraspecific variations and provide additional morphological and morphometric data for the species. This is the first record of S. contortus in K. scorpioides and the first record of the species in the Brazilian Amazon. Our findings expand the known host distribution of S. contortus, highlight host-sharing patterns among parasites of freshwater turtles, and contribute to understanding parasite diversity in K. scorpioides.