Phylogenetic relationships of populations and species within Potamorrhaphis, a genus of freshwater South American needlefishes, were assessed using mitochondrial cytochrome b sequences. Samples were obtained from eight widely distributed localities in the Amazon and Orinoco rivers, and represented all three currently recognized species of Potamorrhaphis. The phylogeny of haplotypes corresponded imperfectly to current morphological species identities: haplotypes from P. guianensis, the most widespread species, did not make up a monophyletic clade. Geography played a strong role in structuring genetic variation: no haplotypes were shared between any localities, indicating restricted gene flow. Possible causes of this pattern include limited dispersal and the effects of current and past geographical barriers. The haplotype phylogeny also showed a complex relationship between fishes from different river basins. Based on the geographical distribution of clades, we hypothesize a connection between the middle Orinoco and Amazon via rivers of the Guianas. More ancient divergence events may have resulted from Miocene alterations of river drainage patterns. We also present limited data for two other Neotropical freshwater needlefish genera: Belonion and Pseudotylosurus. Pseudotylosurus showed evidence of substantial gene flow between distant localities, indicating ecological differences from Potamorrhaphis.

DNA barcoding is a recently proposed global standard in taxonomy based on DNA sequences. The two main goals of DNA barcoding methodology are assignment of specimens to a species and discovery of new species. There are two main underlying assumptions: i) reciprocal monophyly of species, and ii) intraspecific divergence is always less than interspecific divergence. Here we present a phylogenetic analysis of the family Potamotrygonidae based on mitochondrial cytochrome c oxidase I gene, sampling 10 out of the 18 to 20 valid species including two non-described species. Potamotrygonidae systematics is still not fully resolved with several still-to-be-described species while some other species are difficult to delimit due to overlap in morphological characters and because of sharing a complex color patterns. Our results suggest that the family passed through a process of rapid speciation and that the species Potamotrygon motoro, P. scobina, and P. orbignyi share haplotypes extensively. Our results suggest that systems of identification of specimens based on DNA sequences, together with morphological and/or ecological characters, can aid taxonomic studies, but delimitation of new species based on threshold values of genetic distances are overly simplistic and misleading.

Freshwater stingrays (Potamotrygonidae) are the only elasmobranchs completely adapted for living in freshwater and all species studied so far presented a reproductive mode described as matrotrophic viviparity with development of trophonemata. Several specimens were collected, dissected and had their reproductive parameters studied. The following species are being studied: Potamotrygon motoro, P. orbignyi, P. schroederi, P. scobina, Potamotrygon sp., Paratrygon aiereba and Plesiotrygon iwamae. The reproductive cycle in the potamotrygonid species observed is directly related to the hydrologic cycle. All species studied have defined reproductive periods with the following sequence of events: gonadal maturation, copulation, pregnancy, birth and resting. Each species analyzed presented a different reproductive periodicity. Gonadal maturation lasts for an average of about 3 months. Copulation does not happen during the same period of the year for all species and it takes place during the rainy or dry season. The lowest average uterine fecundity observed corresponded to 1 and the highest average value was 8. The gestation period varied and lasted between 3 to 9 months. Birth season also presented variation and may last from 3 to 4 months. A resting interval was observed in the reproductive cycle of most species. It is expected that the observation of reproductive aspects of freshwater stingrays contributes to the understanding of population dynamics of these species.

Specimens of Potamotrygonocestus used in the present taxonomic and phylogenetic study were collected in freshwater potamotrygonids from the Rio Paraná (Puerto Reconquista, Santa Fé, Argentina; 59°42′W, 29°29′S) during February 1995, and from the Amazon region of Brazil during September to December 1996, supplemented by specimens previously deposited in museum collections. Six species of Potamotrygonocestus were recognized (P. amazonensis, P. chaoi sp. n., P. fitzgeraldae sp. n., P. magdalenensis, P. maurae sp. n., P. travassosi), for which an identification key is provided. Potamotrygonocestus orinocoensis is considered a junior synonym of P. travassosi. Additional specimens of Potamotrygonocestus may represent two undescribed species. A phylogenetic analysis of six morphological characters for the six named species of Potamotrygonocestus generated a single tree eight steps long, with a consistency index of 0.87, a retention index of 0.90, and a rescaled consistency index of 0.79 with the following topology: (P. maurae sp. n. ((P. amazonensis + P. magdalenensis) (P. chaoi sp. n. (P. fitzgeraldae sp. n. + P. travassosi)))).

A new species of Potamotrygon is described from the Rio Negro drainage, Amazonas, Brazil. In spite of being cited or pictured several times in the scientific and aquarium fish literature since the 19th Century, it had been misidentified and still lacked a scientific name. Potamotrygon wallacei, n. sp., is diagnosed by the following characters: dorsal surface of disc light brown, with black irregularly-shaped vermiculate markings forming an amphora- or Ω-shaped figure on mid-disc, delimiting light brown reniform areas at disc center, and with subcircular light brown ocellate markings on disc margins; small body size (smallest known Potamotrygon species; largest examined specimen measured 310 mm DW); dorsal spines on tail usually rather low, without broad bases, in one to rarely three irregular rows, but extending posteriorly only to tail mid-length and not to caudal stings, with altogether relatively few spines; denticles on posterior mid-disc and tail base Y-shaped, with a central, anterior, bulbous cusp and usually two posterior pairs of smaller, rounded cusps; and single (anterior) angular cartilage. The new species is similar to P. orbignyi and other "reticulated" species in having a single (anterior) angular cartilage and in the color pattern of the tail, but is easily distinguished based on its size, dorsal tail spine arrangement, and specific details of color pattern.

The objective of this study was to compare and correlate the ecology of neonates and young individuals of Potamotrygon wallacei, Potamotrygon motoro and Paratrygon aiereba with regard to their hematological profile and the physicochemical parameters of the water that they inhabit. Principal component analysis (PCA) on the complete blood count revealed total variation of 72.92%, thus demonstrating a differentiation system for oxygen demand. On the other hand, P. motoro was considered to be an intermediate species, given that its complete blood count characteristics interacted with both P. wallacei and with P. aiereba. The interaction among the biochemical variables was shown to total 64.67% of the factors. This allowed differentiation of P. wallacei from P. aiereba, while P. motoro maintained an intermediate position. These characteristics of differentiation within the preferred environment corroborate the PCA of the present study and confirm that these species can be differentiated through considering the complete blood count and biochemical parameters. The PCA on water properties showed 68.57% differentiation, mainly comprising the x axis (49.44%). It can be affirmed that P. motoro has the capacity to inhabit the preferential areas of P. wallacei and P. aiereba, as well as occupying localities in which other stingrays are not found. In conclusion, P. wallacei presents patterns differentiating it from P. aiereba, while P. motoro is a species that presents intermediate characteristics. The latter can be considered to be a more broadly distributed species regarding its ecophysiological characteristics.Keywords: hematology, potamotrygonids, physiology, differences, ecology. Interações ecofisiológicas e dos parâmetros físico-químico da água em arraias de água doce ResumoEste trabalho tem por objetivo investigar o perfil hematológico e os parâmetros físico-químicos da água, comparando e correlacionando ecologicamente entre neonatos e jovens de Potamotrygon wallacei (arraia cururu), Potamotrygon motoro e Paratrygon aiereba. A análise de componentes principais (PCA) do hemograma revelou um total 72,92% de variação, constituindo-se em um sistema de diferenciação na demanda por oxigênio. P. wallacei apresenta diferenciação no eixo X quando comparada a P. aiereba, por outro lado P. motoro constitui-se como uma espécie intermediária que apresenta as características do hemograma interagindo tanto com P. wallacei quanto com P. aiereba. A interação entre as variáveis bioquímica demonstram um total de 64,67% dos fatores, no qual foi possível diferenciar, a arraia P. wallaceiBraz.

No abstract

The family Potamotrygonidae is monophyletic comprising three genera: Paratrygon Duméril, Potamotrygon Garman and Plesiotrygon Rosa, Castello & Thorson. The distribution of most species in this family is restricted to a single basin or fluvial system. Only Potamotrygon motoro, Potamotrygon orbignyi and Paratrygon aiereba are found in more than one river basin. In this study we investigate genetic structuring of Paratrygon aiereba, from five rivers of the Amazon region: Negro, Solimões-Amazon-Estuary system, Tapajós, Xingu and Araguaia. Sixty-three individuals were sequenced for ATPase 6, and a representative subsample of 27 individuals was sequenced for COI. The COI dataset analysis indicated that Paratrygon is sister to all other potamotrygonid genera and species. Population parameters inferred from the analysis of ATPase 6 sequences revealed that the populations of this species are structured within each river, with no or nearly non-existent gene flow occurring between rivers and a positive correlation between geographic and genetic distances. Paratrygon aiereba is comprised of three geographically restricted clades with K2P interclade distances of at least 2%. Intraspecific divergence within P. aiereba is similar to the interspecific divergence observed in Potamotrygon spp. sampled throughout the same geographic area. Using the premises of COI barcoding and the allopatric distribution of the three P. aiereba clades, the taxon P. aiereba most likely comprises three distinct biological species. Since freshwater stingrays of the family Potamotrygonidae are highly exploited for the aquarium trade, management and conservation strategies need to be implemented at the level of each river basin, rather than at the level of the Amazon basin.A família Potamotrygonidae forma um clado monofilético com três gêneros: Paratrygon Duméril, Potamotrygon Garman e Plesiotrygon Rosa, Castello & Thorson. A maioria das espécies dessa família possui distribuição restrita a uma única bacia ou sistema fluvial, e somente as espécies Potamotrygon motoro, Potamotrygon orbignyi e Paratrygon aiereba estão presentes em mais de uma bacia hidrográfica. O presente estudo teve como objetivo investigar a estrutura genética de Paratrygon aiereba em alguns rios da região Amazônica: Negro, sistema Solimões-Amazonas, Tapajós, Xingu, e Araguaia. Para tal foram utilizados como marcador molecular os genes de ATPase subunidade 6, e COI. As análises com o fragmento de COI indicaram que o gênero Paratrygon é grupo irmão dos outros gêneros da família potamotrygonidae. Os resultados para o fragmento de ATPase mostraram que essas populações estão estruturadas dentro dos rios, com fluxo gênico restrito, ou mesmo sem fluxo gênico, apresentando uma correlação positiva entre distância genética e distância geográfica. Paratrygon aiereba é composta por três clados com distância genética de pelo menos 2%. A divergência encontrada dentro desse grupo é semelhante à observada entre Potamotrygon spp. Segundo as premissas para barcoding COI e a distribuição alopátrica de...