Abstract
Abstract Birds of the genus Pachyptila (prions) are small seabirds typical of the Southern Ocean, a region that harbors the greatest diversity of Procellariiformes. The Antarctic prion (Pachyptila desolata), classified as of low conservation concern, is a pelagic species that feeds primarily on small planktonic crustaceans and forms large aggregations in plankton-rich areas. Although it is a subantarctic species, its occurrence in Brazil includes coastal records from Rio de Janeiro to southern Bahia, albeit rare and poorly updated, as is the information regarding its parasitic fauna. The present study documents the first record of parasites in P. desolata in northeastern Brazil, contributing to knowledge of its distribution and parasitic associations in the country. Two juvenile specimens were rescued under the Sergipe/Alagoas Basin Beach Monitoring Project – Petrobras (PMP-SEAL) between July and August 2025; one individual was found dead, and the other was found alive but exhibited polytrauma and died a few days later during the rehabilitation process. Both specimens were subjected to necropsy, and the parasites collected during the procedure were properly preserved and forwarded for parasitological analysis. Six parasite taxa were identified, comprising four species of chewing lice: Ancistrona vagelli, Austromenopon stammeri, Naubates prioni and Saemundssonia desolata, and two nematodes, Seuratia shipleyi and Contracaecum sp. [larva]. Detailed illustrations are provided to assist in the identification of the observed parasites. This study provides the first record of A. vagelli in P. desolata in Brazil. In addition, the known geographic distributions of A. stammeri and N. prioni are extended to northeastern Brazil, as these species had previously been recorded only in the state of Rio de Janeiro. Pachyptila desolata is also reported as a new host for the nematodes S. shipleyi and Contracaecum sp. These findings provide important baseline data for future ecological and biogeographical investigations of host-parasite interactions involving seabirds in the South Atlantic.