A new species of Kalicephalus (Nematoda: Diaphanocephalidae), a parasite of Bothrops atrox (Serpentes: Viperidae) from the Brazilian Amazon.

Kalicephalus (Molin, 1861) comprises 33 species of gastrointestinal snake and lizard parasites with a cosmopolitan distribution, with seven taxa occurring in the Neotropical realm. In the present study, we describe Kalicephalus atroxi n. sp., found parasitising the snake Bothrops atrox, from the Eastern Amazon in the State of Amapá, North of Brazil. We used an integrative approach that included light microscopy, scanning electron microscopy, and sequencing of the internal transcribed spacer 1 (ITS1) region to describe Kalicephalus atroxi n. sp. The new species has a buccal capsule characteristic of the genus, a slight cuticular inflation in the cephalic region. The females have an amphidelphic reproductive system, a vulva with prominent lips, and a long tail, tapering posteriorly. The males have long and alate spicules, and the copulatory bursa is lobed with dorsal rays with distinct morphology compared to their congeners. Molecular analyses and phylogenetic reconstructions cluster the new species into a well-supported clade with K. costatus costatus, from Chironius fuscus, from the same locality in northern Brazil. Kalicephalus atroxi n. sp. is the eighth species of the genus in the Neotropics, the seventh in Brazil, the second described parasitising B. atrox in Brazil, and the first species of snake nematode described in the State of Amapá.