Stranded Antarctic Prions Reveal Hidden Parasite Fauna on Brazil’s Northeast Coast

When two small seabirds washed ashore on the beaches of Aracaju, in the Brazilian state of Sergipe, the monitoring teams of the Sergipe-Alagoas Basin Beach Monitoring Project, run under the Petrobras-sponsored PMP-SEAL program, had little reason to suspect that the birds would rewrite a small corner of parasitology. The animals were Antarctic prions, Pachyptila desolata, pelagic members of the petrel family that spend most of their lives far to the south, skimming plankton from the cold waters of the Southern Ocean. Their appearance on a tropical coastline thousands of kilometers north of their usual range was already noteworthy. What the birds carried, however, proved to be even more remarkable: a community of parasites that includes species never before documented on this host in Brazil, and two worm species for which the Antarctic prion had never been recorded as a host anywhere in the world.

The findings, published in the journal Discover Ecology by a team led by André Mota Alves of the Fundação Mamíferos Aquáticos and the Universidade Federal de Sergipe, represent the first parasitological record of Pachyptila desolata in northeastern Brazil. Between July and August 2025, one of the two juvenile birds was found dead on the beach, while the other was rescued alive but in poor condition. The rescued individual presented a grim clinical picture: polytrauma with dislocation of the right tarsal-phalangeal joint, exposed bone in the proximal right phalanges, a bone callus on the left tibia, restricted movement of the left tibiotarsal joint, and a swollen, displaced tail suggesting a possible fracture of the pygostyle. The bird was also dehydrated, in low body condition, and bore whitish plaques on the tongue and multiple lacerations. Despite intensive care at the Centro de Reabilitação e Despetrolização of the Fundação Mamíferos Aquáticos in São Cristóvão, including antiparasitic treatment with cypermethrin and carbaryl against ectoparasites, the animal died a few days later and was sent for necropsy alongside the carcass of the first specimen.

Necropsy of the two juveniles, one male and one female, yielded a total of 31 parasites distributed across six taxa. Four species of chewing lice were recovered from the feathers: Ancistrona vagelli, Austromenopon stammeri, Naubates prioni, and Saemundssonia desolata. Two nematodes were found in the stomachs: Seuratia shipleyi, a member of the family Acuariidae, and a larval Contracaecum sp. from the family Anisakidae. The distribution between hosts was strikingly uneven. The male found alive harbored only the two helminth taxa and no ectoparasites, a result the authors attribute in part to the antiparasitic treatment administered on arrival at the rehabilitation center. The female found dead, by contrast, carried the full complement of six taxa, offering the researchers a far richer picture of the parasite community riding on this single vagrant seabird.

The most consequential of the ectoparasite findings concerns Ancistrona vagelli, a chewing louse recognized as the largest representative of the family Menoponidae. The specimens recovered from the stranded female were robust adults, so large and heavy-bodied that standard slide mounting proved impossible, complicating the visualization of fine structures such as antennae, mouthparts, and genitalia. Even so, the species’ distinctive morphology, a yellowish, dorsoventrally compressed body with brownish tones, a semicircular head with a deeply emarginated posterior margin, and a large bipartite corneous process on the ventral surface, allowed confident identification. This is the first record of A. vagelli on Pachyptila desolata in Brazil. The species had previously been reported from the Antarctic prion only in New Zealand and on subantarctic islands, where earlier authors recorded the genus Ancistrona without specifying the species. Because A. vagelli is currently considered the only valid species in the genus, those older records may well correspond to the same louse now documented on the Brazilian coast.

Three further louse species extended the known geographic ranges of parasite-host associations within Brazil. Austromenopon stammeri, Naubates prioni, and Saemundssonia desolata had previously been recorded on P. desolata only in the state of Rio de Janeiro, in a 2006 survey of chewing lice associated with albatrosses and petrels collected in Brazil. The new records push those distributions more than two thousand kilometers northward into the tropical Northeast. The morphological work accompanying these identifications carries independent taxonomic value. For N. prioni, the team provides updated illustrations of male and female antennae and poststernal plates, structures that earlier descriptions left unillustrated and that can hinder species identification. For S. desolata, a louse known for its strict host specificity to prions of the genus Pachyptila, the study supplies the first detailed illustrations of the clypeal signature, antennal segmentation, and male genitalia, including chaetotaxy that had been underrepresented in the existing literature.

The endoparasite findings are, if anything, more novel. No helminths had ever been reported from Pachyptila desolata in the scientific literature, making the Antarctic prion a new host record for both Seuratia shipleyi and Contracaecum sp. Seuratia shipleyi is a nematode frequently encountered in the stomachs of seabirds across Antarctic, subantarctic, tropical, and subtropical waters. The specimens recovered from the prions displayed the diagnostic features of the species: a thick cuticle bearing four longitudinal rows of spines, a bilobed cephalic hood armed with 74 progressively arranged spines, 37 on each side, three cervical spines sharing a common base, and, in the male, two conspicuously unequal spicules. Contracaecum larvae, identified only to genus, showed the typical three underdeveloped ventrolateral lips, a rounded ventricle with a ventricular appendix, and an intestinal caecum extending halfway along the esophagus. Both nematode genera are transmitted through trophic pathways, relying on fish and other aquatic organisms as intermediate or paratenic hosts, a life cycle entirely consistent with the prion’s diet of small planktonic crustaceans, fish, and squid.

To place these findings in context, the authors conducted a systematic survey of the global literature and found that only 11 studies worldwide have ever reported parasitological findings in Pachyptila desolata. The accumulated records span the species’ circumpolar domain, from the South Orkney Islands, South Georgia, and the Falkland Islands to Heard Island, Kerguelen, Macquarie Island, Tasmania, New Zealand, Chile, and Australia, and encompass chewing lice of the genera Austromenopon, Longimenopon, Naubates, Halipeurus, Saemundssonia, and Ancistrona, fleas of the genera Notiopsylla and Parapsyllus, the tick Ixodes kerguelenensis, and feather mites such as Zachvatkinia graciosa and species of Brephosceles. The louse species recovered in the new study, particularly A. stammeri, N. prioni, and S. desolata, recur across this range and appear largely restricted to birds of the genus Pachyptila, a pattern the authors interpret as suggestive of a long history of coevolution between prions and their mallophagan lice, though they caution that a complete host distribution list for these parasites remains to be documented.

The biogeographic implications extend beyond parasitology proper. The most recent parasitological record of P. desolata outside the Antarctic and subantarctic domain before this study was the Rio de Janeiro work published in 2006, and the two decades separating that survey from the present one underscore how sparse the data are for lower latitudes. Parasite communities with high host specificity can act as biological markers of host population connectivity, and records such as these hint at migratory or dispersive movements of Antarctic prions into tropical and subtropical Atlantic waters, possibly reflecting contact on wintering grounds or oceanographic events that carry weakened juvenile birds northward. Brazilian coastal records of the species, which range from Rio de Janeiro to southern Bahia, have always been rare and poorly updated, and the Sergipe specimens now extend that documented coastal presence to a state where the species had not previously been reported.

The authors are careful to frame the scope of their conclusions. With only two stranded juvenile birds examined, parasitological indices could not be calculated, and the sample cannot be taken as representative of the parasite fauna of the species as a whole. Ethical and legal constraints were nonetheless fully observed: the study involved no capture or experimental manipulation of live vertebrates, all parasite material was obtained opportunistically from carcasses within the framework of the federally licensed beach monitoring program, and collection was authorized under IBAMA license ABIO No. 1224/2019. The parasite specimens themselves are deposited in the collection curated by the Fundação Mamíferos Aquáticos under accession numbers 467315 and 137380, ensuring that the physical evidence remains available for future study.

What the study ultimately delivers is a baseline. The first Brazilian record of Ancistrona vagelli on the Antarctic prion, the northeastward extension of three louse species previously known in the country only from Rio de Janeiro, and the first helminth records for the host species anywhere together fill conspicuous gaps in a literature that has barely been touched since the mid-twentieth century. The detailed illustrations and morphological descriptions, prepared with stereomicroscopy, light microscopy, potassium hydroxide clearing, and Hoyer’s medium mounting, strengthen the taxonomic foundation for identifying ectoparasites of Procellariiformes, a group whose louse faunas have long been recognized as a window into seabird evolutionary history. For a species classified as of Least Concern by the IUCN but whose parasite fauna remains, in the authors’ words, still underexplored, the two small carcasses from an Aracaju beach demonstrate how much biological information can be recovered from animals that, by the time they reach a tropical shoreline, have already run out of luck.

Subject of Research: Parasite fauna of the Antarctic prion Pachyptila desolata stranded on the northeastern coast of Brazil

Article Title: Notes on the parasite fauna of Pachyptila desolata in the coastal zone of Northeast Brazil

Article References: Alves, A. M., Figueiredo, L. M., Santos Rodrigues, T. D., Simões, S. R. J. S., dos Santos, E. F., de Medeiros, I. G., de Brito, E. K., Boldrini, M. A., Lux Hoppe, E. G., Santana Lima, V. F., & Gomes Borges, J. C. (2026). Notes on the parasite fauna of Pachyptila desolata in the coastal zone of Northeast Brazil. Discover Ecology, 2(1), Article 22. https://doi.org/10.1007/s44396-026-00041-0

Image Credits: AI Generated

DOI: 10.1007/s44396-026-00041-0

Keywords: Antarctic prion, Pachyptila desolata, chewing lice, Ancistrona vagelli, Seuratia shipleyi, Contracaecum, seabird parasites, northeastern Brazil, Procellariiformes, host-parasite interactions, beach monitoring, biogeography