Ticks (Parasitiformes: Ixodida) comprise about 1008 species worldwide, distributed among the families Argasidae, Ixodidae, and Nuttalliellidae. In the Neotropics, the family Ixodidae represents approximately 14% of global diversity and includes genera of medical and veterinary importance such as Amblyomma, Dermacentor, Haemaphysalis, Ixodes, and Rhipicephalus. However, the taxonomic delimitation and distribution of several neotropical species remain uncertain due to the existence of cryptic species complexes, unreliable historical records, and the lack of consistent morphological descriptions or molecular analyses. The Neotropical species Amblyomma crassum Robinson, 1926 represents a case of taxonomic ambiguity, as only females are known; it shows morphological similarities with other species, some of its records have been questioned, and molecular information is scarce. In this study, adult (females) and immature (nymphs) specimens of A. crassum are reported and confirmed morphologically and molecularly, providing the description of the nymphal stage. Additionally, the association of A. crassum with wildlife hosts from Brazil and Colombia is recorded, including amphibians (Rhinella marina), reptiles (Iguana iguana), and mammals (Didelphis albiventris and Didelphis marsupialis). Our results expand knowledge about tick diversity in the Neotropics and validate the taxonomic identity of A. crassum, based on the morphological description of the nymph and confirmation of certain morphological differences in adults (females) compared to species that have traditionally caused confusion, such as Amblyomma humerale and Amblyomma sabanerae.
Martínez‐Sánchez et al. (Fri,) studied this question.