An integrative approach method reveals the presence of a previously unreported species of Imparfinis Eigenmann and Norris 1900 (Siluriformes: Heptapteridae) in Argentina

Specimens of Imparfinis were recently collected in north-western Argentina from the Bermejo River basin (Salta and Jujuy Provinces), del Valle River (Salta Province) and Horcones River (Santiago del Estero Province). An integrative approach to taxonomy, combining a detailed morphological study and molecular phylogenetic analyses, was applied to determine the species identity of these specimens. A principal components analysis of morphological data clustered the specimens from north-western Argentina and from the Amazon basin, indicating a close morphological resemblance. Also, a molecular phylogenetic analysis showed populations of I. guttatus from Argentina and Peru forming a clade. According to the conducted haplotype network analysis these populations are distinct in two mutations. Thus, in the absence of morphological or molecular data indicating the contrary, the combined method supports the identity of the specimens from the tributaries of the Paraguay River in Argentina as I. guttatus, whose type locality is in the upper Beni River basin in Bolivia. This contribution is also the first record for this species from Argentina. The disjunct distribution of I. guttatus provides new evidence reinforcing the hypothesis for the origin of the Paraguayan ichthyofauna. We also provide an approach to the phylogenetic relationships of Imparfinis in Heptapteridae.

Neuroanatomical and neurophysiological mechanisms of acoustic and weakly electric signaling in synodontid catfish

To what extent do modifications in the nervous system and peripheral effectors contribute to novel behaviors? Using a combination of morphometric analysis, neuroanatomical tract‐tracing, and intracellular neuronal recording, we address this question in a sound‐producing and a weakly electric species of synodontid catfish, Synodontis grandiops, and Synodontis nigriventris, respectively. The same peripheral mechanism, a bilateral pair of protractor muscles associated with vertebral processes (elastic spring mechanism), is involved in both signaling systems. Although there were dramatic species differences in several morphometric measures, electromyograms provided strong evidence that simultaneous activation of paired protractor muscles accounts for an individual sound and electric discharge pulse. While the general architecture of the neural network and the intrinsic properties of the motoneuron population driving each target was largely similar, differences could contribute to species‐specific patterns in electromyograms and the associated pulse repetition rate of sounds and electric discharges. Together, the results suggest that adaptive changes in both peripheral and central characters underlie the transition from an ancestral sound to a derived electric discharge producing system, and thus the evolution of a novel communication channel among synodontid catfish. Similarities with characters in other sonic and weakly electric teleost fish provide a striking example of convergent evolution in functional adaptations underlying the evolution of the two signaling systems among distantly related taxa.

(Monogenea: Dactylogyridae) from Brazilian catfishes: new species, molecular data and new morphological contributions to the genus

This study describes two new species, Trinigyrus anthus n. sp. and Trinigyrus carvalhoi n. sp., from gills of Hypostomus spp. from the Upper Paraná River basin, Brazil. Trinigyrus peregrinus is redescribed based on examination of its holotype, paratypes and new material of specimens parasitizing Pterygoplichthys ambrosettii, also from the Upper Paraná River basin, Brazil. New morphological features were included in the diagnosis of the genus, such as the presence of a sclerotized border on the anchor base, and a weakly sclerotized fringe on the base of the male copulatory organ (MCO). Trinigyrus anthus n. sp. differs from other congeners by the shape of the MCO, presenting an enlarged base with sclerotized fringes resembling flower petals. Trinigyrus carvalhoi n. sp. and T. peregrinus are similar but can be differentiated from each other mainly by the sclerotization of the vagina (absent in the new species), and the morphology of the MCO (C-shaped versus one counterclockwise circle, respectively). For the first time, gene sequences of Trinigyrus spp. from Brazil were obtained (partial ribosomal 28S and mitochondrial cytochrome c oxidase I (mtCOI)). The genetic divergences among the new species and T. peregrinus varied from 2 to 3% (6‒18 pb) based on sequences of 28S ribosomal DNA (rDNA), and 6-7% (83‒92 pb) using mtCOI. Phylogenetic analyses based on partial 28S rDNA revealed that Trinigyrus, Heteropriapulus and Unilatus formed a monophyletic and well-supported clade of monogeneans from Neotropical freshwater loricariids, suggesting a closer relationship among these dactylogyrids and their hosts.

Contrasting geographic structure in evolutionarily divergent Lake Tanganyika catfishes

Geographic isolation is suggested to be among the most important processes in the generation of cichlid fish diversity in East Africa's Great Lakes, both through isolation by distance and fluctuating connectivity caused by changing lake levels. However, even broad scale phylogeographic patterns are currently unknown in many non-cichlid littoral taxa from these systems. To begin to address this, we generated restriction-site-associated DNA sequence (RADseq) data to investigate phylogeographic structure throughout Lake Tanganyika (LT) in two broadly sympatric rocky shore catfish species from independent evolutionary radiations with differing behaviors: the mouthbrooding claroteine, Lophiobagrus cyclurus, and the brood-parasite mochokid, Synodontis multipunctatus. Our results indicated contrasting patterns between these species, with strong lake-wide phylogeographic signal in L. cyclurus including a deep divergence between the northern and southern lake basins. Further structuring of these populations was observed across a heterogeneous habitat over much smaller distances. Strong population growth was observed in L. cyclurus sampled from shallow shorelines, suggesting population growth associated with the colonization of new habitats following lake-level rises. Conversely, S. multipunctatus, which occupies a broader depth range, showed little phylogeographic structure and lower rates of population growth. Our findings suggest that isolation by distance and/or habitat barriers may play a role in the divergence of non-cichlid fishes in LT, but this effect varies by species.

Taxonomic revision of the South American catfish genus Ageneiosus (Siluriformes: Auchenipteridae) with the description of four new species

The catfish genus Ageneiosus in the exclusively Neotropical family Auchenipteridae is revised. Species of Ageneiosus are widely distributed in all major South American continental drainages except the São Francisco River basin and small rivers along the Brazilian east coast. The taxonomic revision was based on examination of available type specimens, additional museum material and comparisons of original descriptions. A suite of morphometric, meristic and qualitative characters of internal and external anatomy were used to diagnose valid species and determine synonyms. Thirteen valid species are recognized in the genus Ageneiosus, some of which are widely distributed across South America. Ageneiosus pardalis is the only trans-Andean species in the genus. Ageneiosus polystictus and Ageneiosus uranophthalmus are more widely distributed than previously reported. Ageneiosus marmoratus is a junior synonym of Ageneiosus inermis. Ageneiosus dentatus is a valid species and its name is removed from the synonymy of Ageneiosus ucayalensis. Four new species are described: Ageneiosus akamai, Ageneiosus apiaka, Ageneiosus intrusus and Ageneiosus lineatus, all from the Amazon River basin. A dichotomous key for all 13 valid species of Ageneiosus species is provided.

Neoplecostomus doceensis: a new loricariid species (Teleostei, Siluriformes) from the rio Doce basin and comments about its putative origin

A new species of Neoplecostomus is described from the rio Doce basin representing the first species of this genus in the basin. The new species is distinguished from its congeners by having enlarged, fleshy folds between dentaries, two or three series of developed papillae anterior to premaxillary teeth and a adipose-fin membrane present, and by lacking enlarged odontodes along snout lateral margins in mature males, a well-developed dorsal-fin spinelet wider than dorsal-fin spine base, lower number of lateral-line figs and developed membrane on the dorsal portion of the first, second and third pelvic-fin branched rays. Additionally, we present a brief discussion of biogeographic scenarios that may explain the distribution of the new species in the rio Doce basin. We suggested that the ancestral lineage of the new species reached the rio Doce from the upper portions of rio Paraná drainages about 3.5 Mya (95% HPD: 1.6-5.5) indicating a colonization route of the N. doceensis ancestral lineage from the south end of Serra do Espinhaço, probably as a result of headwater capture processes between the upper rio Paraná and rio Doce basins.

Design of mini-barcode for catfishes for assessment of archival biodiversity

Recovery of DNA barcode sequences is often challenging from the archived specimens. However, short fragments of DNA may be recovered, which would significantly improve many unresolved taxonomic conflicts. Here, we designed a mini-barcode for catfishes comprising several species and many cryptic taxa. We analysed a data set of 3048 publicly available COI barcode sequences representing 547 worldwide catfish species and performed 152 628 interspecies comparisons. A significantly more positively correlated interspecies distance was detected with transversion (0.78, P < 0.001) than with transition (0.70, P < 0.001). This suggested that transversions were better diagnostics for species identification. In the aligned data set, two transversion-rich fragments (53 bp and 119 bp) were identified. Transition/transversion bias value was 1.04 in 53-bp fragment, 1.23 in 119-bp fragment and 1.50 in full-length barcode. The interspecies distance with full-length barcode was 0.212 ± 0.037, while that with 53-bp and 119-bp fragments was 0.325 ± 0.039 and 0.218 ± 0.045, respectively. Survey of 53-bp fragment showed a possibility of only 1144 barcodes, while that of 119-bp fragment showed >4 million barcodes. Thus, the 119-bp fragment is a viable mini-barcode for catfishes comprising >3000 extant species. Experiment with 82 archived catfishes showed successful recovery of this mini-barcode using the designed primer. The mini-barcode sequences showed species-specific similarity in the range of 98-100% with the global database. Therefore, survey of a transversion-rich fragment within the full-length barcode would be an ideal approach of mini-barcode design for biodiversity assessment.