Exploring the diversity of Brazilian camallanids: a checklist of the family Camallanidae (Nematoda) from Brazil with a new key to identification of the genera in the family

Abstract The family Camallanidae includes nematodes traditionally classified based on the morphology of their buccal capsules. However, several questions have been raised about the validity of these characteristics for their classification. Despite having a remarkable diversity, our knowledge of camallanids in Brazil remains limited, leaving gaps in our understanding of the true species diversity in the country, their geographical distribution and host species associations. Therefore, this study presents a checklist of species in the family Camallanidae recorded in Brazil, including a review for the classificationa and new dichotomous key for identifying the genera. Camallanidae comprises 2 subfamilies with 13 valid genera, classified based on the morphology of the buccal capsule and trident, and on the presence, shape and distribution of internal ridges on the capsule. Thirty-seven species, distributed across 7 genera, have been recorded in Brazil so far, parasitizing 276 host taxa, including fish, chelonians and snakes, with no records of these nematodes parasitizing amphibians in the country. We reallocated five species of Spirocamallanus and 2 species of Procamallanus to Denticamallanus , and 1 species of Camallanus was reallocated to Serpinema. Spirocamallanus is the most diverse genus, with 16 species, and Spirocamallanus inopinatus exhibited the highest host taxa association diversity (144) and the widest geographical distribution. Until further molecular studies are conducted, the new dichotomous key presented in this checklist contributes to a better understanding of the classification of the family Camallanidae, based on the morphology of the buccal capsule and accessory structures.