A new species of Characidium (Characiformes: Crenuchidae) from the rio Doce basin, Brazil

Abstract

A new species of Characidium is described from the tributaries of the upper and middle rio Doce basin, Minas Gerais, Brazil. The new species is distinguished from most congeners, except C. cricarense, C. hasemani, C. helmeri, C. kalunga, C. pterostictum, C. schubarti, C. summus, and C. travassosi by lacking scales in the area between the anterior limit of the isthmus and the anterior margin of cleithrum. The new species differs from the aforementioned species by a series of characters, including the presence of the adipose fin, 2–4 scales between the anus and anal fin, two rows of dentary teeth, presence of the parietal branch of the supraorbital canal, 4 scale rows above the lateral line, and absence of two conspicuous inclined dark bands on each caudal-fin lobe. The new species further differs from most congeners with an unscaled ventral surface of the isthmus by the presence of 33–34 pored scales on the lateral line and by the dark dashes on the caudal fin-rays not forming well-defined bands.

Past riverine connectivity effects in population structure and distribution of an endemic freshwater fish from northeastern Brazilian rivers: Phylogeographic, taxonomic, and conservation implications

“…A recent molecular study (including both phylogenetic analysis and species delimitation) identified two distinct lineages within C. bahiense, which clustered as paraphyletic groups (Oliveira-Silva, 2022). Our results based on mtDNA also support these two groups and recovered C. bahiense as a non-monophyletic species (see Figure 1).…”

“…In addition, the taxon sampling also included 4 specimens of C. cf. lagosantense due to its close phylogenetic relationship with C. bahiense (see Oliveira-Silva, 2022). The samples of C. cf.…”

“…bahiense have been reported, respectively, to Sapão River, a tributary of the Preto River (São Francisco freshwater ecoregion-SF) (Lima & Caires, 2011) and to the Piauí River, a tributary of the Parnaíba River (Parnaíba freshwater ecoregion-PA) (Ramos et al, 2014: Figure 1a). A recent study for delimitation of Characidium species from the freshwater ecoregions in northeastern Brazil revealed population differentiation between the specimens from the Sapão River and other populations attributed to C. bahiense, forming two distinct clades based on cytochrome c oxidase subunit I (COI) sequences (see Oliveira-Silva, 2022). (SF ecoregion).…”

“…(SF ecoregion). In addition, traditional morphological data did not recover differences between the specimens from the Sapão River and the others attributed to C. bahiense (Oliveira-Silva, 2022). Thus, the inconsistencies in the species delimitation based on both mitochondrial DNA (mtDNA) and morphological data of C. bahiense, associated with its disjunct geographical distribution in three different freshwater ecoregions, make this species ideal to investigate the role of disjunct distribution through distinct river basins on taxonomic boundaries and biogeographic history.…”