Diversity of Lice (Phthiraptera) on Brown Noddies (Anous stolidus) Stranded on the Northeastern Coast of Brazil: New Host and Locality Records

The Brown Noddy (Anous stolidus) is a widely distributed tropical seabird whose parasitic fauna remains poorly studied, particularly in the southwestern Atlantic. This study aimed to characterize the louse fauna (Phthiraptera) of An. stolidus specimens stranded in northeastern coast of Brazil between April 2024 and October 2025. Sixteen individuals from the Sergipe-Alagoas Basin Beach Monitoring Project were examined. During physical examinations and necropsies, ectoparasites were collected, preserved, and identified using standardized morphological techniques. Of the specimens examined, 13 birds were infested, yielding a total of 191 lice belonging to five species: Actornithophilus piceus, Austromenopon atrofulvum, Quadraceps separatus, Quadraceps birostris, and Saemundssonia remota. More lice were collected from male birds (156 lice collected) than from female birds (35 lice collected). Mean intensity ranged from 1.0 (Au. atrofulvum) to 11.0 (Q. birostris), whereas mean abundance ranged from 0.14 to 6.00, indicating low-to-moderate levels of infestation. Notably, this study provides the first records of Ac. piceus and Q. birostris in Brazil, as well as the first records of both species from An. stolidus, thereby expanding the known geographic distribution and host range of these ectoparasites. The remaining records corroborate previously documented associations with birds of the family Laridae. Although lice were present, there was no evidence that they caused harmful effects or contributed to the deaths of their hosts. These findings indicate that the parasitic diversity of An. stolidus in the region remains underestimated, reinforcing the need for systematic surveys with larger sample sizes and broader geographic coverage to achieve a more robust understanding of host–parasite interactions in the South Atlantic.