Overcoming chemical barriers: a new species of <i>Rhabdias</i> (Nematoda: Rhabdiasidae) from <i>Dendrobates tinctorius</i> (Anura: Dendrobatidae) in the Brazilian Amazon

The nematode genus <i>Rhabdias</i> comprises over 100 species of parasitic nematodes that infect amphibians and reptiles, with a wide geographical distribution. To date, 25 species have been reported from the Neotropical region. Despite this diversity, few integrative studies, combining morphological and molecular data have been conducted to characterize species within the genus. Therefore, the main objective of the present study is to describe, through an integrative approach, a new species of <i>Rhabdias</i> found parasitizing the lungs of an anuran with a high concentration of skin toxins, <i>Dendrobates tinctorius</i>, from the Brazilian Amazon. The new species of <i>Rhabdias</i> is characterized by an elongated body, uniform cuticular inflation attenuated at the extremities, 4 submedian lips and 2 lateral lips, a cup-shaped buccal capsule, and an elongated tail. The morphology of the buccal capsule in <i>Rhabdias camposi</i> n. sp. is also unique among <i>Rhabdias</i> representatives, as this morphological character is known so far. Thus, we emphasize that a detailed study of this morphological trait for species of the genus will be crucial for species diagnosis. Molecular and phylogenetic analyses were performed using mitochondrial COI gene sequences. We observed that the new taxon is closely related to <i>Rhabdias waiapi</i>, a parasite of <i>Pristimantis chiastonotus. Rhabdias camposi</i> n. sp. represents the 26th species of the genus reported from the Neotropics in amphibians and the first described from a <i>Dendrobates tinctorius</i> host in Brazil.