The Hoplias malabaricus group encompasses six valid species and still is believed to harbors cryptic diversity. In this work, an integrative approach including morphological, DNA barcoding, and cytogenetic considerations was conducted to characterize a population of H. malabaricus from the Amazon basin that was recently allocated in the same mitochondrial lineage with H. misionera, a species originally described from La Plata basin. The DNA barcoding analysis revealed that the Amazon population nested together with H. misionera specimens from the La Plata basin (BIN AAB1732) in the same cluster. The intragroup distance (0.5%) was 12 times lower than the nearest neighbor (6%) distance. The morphometric analysis demonstrated slightly variation between Amazon and La Plata populations, being the former composed by larger specimens. Further morphological data supported the molecular evidence of H. misionera inhabiting Amazon basin. The karyotype characterization of H. misionera in the Amazon population showed 2n=40 and karyotypic formulae 20m+20sm, that added to C-banding, Ag-NOR and 18S results are suggestive of the similarity to karyomorph C of H. malabaricus. This work reveals the first record of H. misionera outside of La Plata basin and expands the species distribution for 2500 km northward until the Marajó Island, estuary of Amazonas River.

Morphological and molecular evidence for a new species of longnose skate (Rajiformes: Rajidae: Dipturus ) from Argentinean waters based on DNA barcoding

Zearaja chilensis has been reported from Southern Brazil in the Southwest Atlantic (SWA) to northern Chile in the Southeast Pacific (SEP), and it was listed as vulnerable by the IUCN. Recent molecular studies have called into question the conspecificity between specimens from these opposite coasts of South America, which can have implications for the conservation status of the species. To verify the identity of specimens identified as Z . chilensis , 47 individuals from SWA and 22 from SEP were examined. By comparing external morphology, spinulation pattern, clasper, egg cases, and mitochondrial cytochrome c oxidase I (COI) sequence data, differences between groups were found. Adults from SWA presented longer snout length and shorter tail than those from SEP. Dermal denticles were restricted to the rostral area in SWA skates, whereas in SEP skates most of the dorsal surface was covered with denticles. Marked differences in the morphology of several components of clasper were noticeable. Egg cases of SWA skates had thinner lateral keels than those of SEP. Molecular analysis revealed two well-defined cohesive clusters, corresponding to SWA and SEP specimens, respectively. Average K2P distance between groups was 3.4%, higher than expected for intraspecific differences, and sequences were assigned to different BINs. These integrative approaches strongly support that specimens from SWA known as Z . chilensis correspond to a different nominal species than those from SEP. Herein, Z . brevicaudata (Marini 1933) is resurrected from synonymy with Z . chilensi s.

The family Sciaenidae comprises about 300 species. The black drum Pogonias cromis was the only valid species of the genus. Herein, Pogonias courbina Lacepède 1803 is redescribed based on morphological and molecular evidence and a neotype is designated. Pogonias courbina is distinguished by the following characters: the occurrence of characteristic thickening of the dorsal spines VII to XI in all specimens larger than 250 mm SL; all pterygiophores in the dorsal-fin laminar, thin; anal-fin pterygiophores slender excluded those of spines; lateral projections of gas bladder with few finger-like projections; genetic distance between both species 1%; exclusive occurrence of characters in six informative sites of COI (58 G; 214 G; 328 A; 331 A; 553C; 580 G). The method Automatic Barcode gap Discovery detected gaps in nucleotid distance congruent with the NJ, MP, and ML tree analysis. Also, advertisement calls are three times shorter in duration in P. courbina than in P. cromis. In addition, two monophyletic groups for P. cromis and P. courbina appear in trees obtained with different methodologies, emphasizing the absence of shared haplotypes. A gap of about 8000 km occurs in the distribution of both species along coastal areas of the Atlantic Ocean.

The Squalus genus comprises a group of small demersal sharks occurring circumglobally, popularly known as dogfish sharks. This genus exhibits a conserved morphology, thus making correct morphological identification difficult. Considering these taxonomic problems and the scarcity of molecular data, the present study aimed to identify Squalus genus MOTUs, using DNA barcoding for species delimitation via ABGD (automatic barcode gap discovery), PTP (Poisson tree process), and GMYC (general mixed Yule coalescent) employing the mitochondrial COI gene. A total of 69 sequences were generated from samples obtained from the American coast in both the Atlantic and Pacific Oceans. The ABGD analysis was the most conservative among the three applied delimitations, indicating three taxonomic units, while the PTP analysis revealed nine MOTUs, with two conflicting units noted between S. clarkae + S. mitsukurii and S. albicaudus + S. cubensis. The GMYC analysis indicated an excessive division, with S. acanthias and S. mitsukurii subdivided into six MOTUs each and S. blainville, into four. These findings demonstrated that Squalus presents a complex of previously defined species, with misidentified samples deposited in databases leading to difficulties in analyzing the real distribution and diversity of species belonging to this genus. Thus, further efforts to highlight possible new species are recommended.