Cytogenetics and DNA barcode reveal an undescribed Apareiodon species (Characiformes: Parodontidae)

Parodontidae is a small group of fish and some species are particularly difficult to identify due to the lack of sufficiently consistent morphological traits. Cytogenetically, the species possess 2n = 54 chromosomes and are either sex-homomorphic or sex-heteromorphic (regarding its chromosomes). We evaluated data on color, tooth morphology, cytogenetics, and mitochondrial markers (COI) in Apareiodon specimens from the Aripuanã River (Amazon basin) and the results were compared to other congeneric taxa. Morphological results show an overlap of body color and tooth morphology to other known Apareiodon. The cytogenetics data showed that the 2n = 54 chromosomes, 50 m/sm + 4 st and, a ZZ/ZW sex chromosome system in Apareiodon sp. are common to other species of the genus. However, the number and chromosomal localization of the 45S ribosomal and pPh2004 satellite DNA sites, in addition to W chromosome localization of the pPh2004 appear to be exclusive cytogenetic features in Apareiodon sp. Our phylogenetic tree revealed well-supported clades and confirmed, by barcode species delimitation analysis, a new Molecular Operational Taxonomic Unit (MOTU) for Apareiodon sp. (Aripuanã River). As a whole, the above features support the occurrence of a new species of the Apareiodon, thus far unknown for the Parodontidae.