Phylogeography of Baryancistrus xanthellus (Siluriformes: Loricariidae), a rheophilic catfish endemic to the Xingu River basin in eastern Amazonia.

Baryancistrus xanthellus (Loricariidae) is an endemic fish species from the Xingu River basin with its life history in the shallow rapid waters flowing over bedrock substrates. In order to investigate the genetic diversity and demographic history of B. xanthellus we analyzed sequence data for one mitochondrial gene (Cyt b) and introns 1 and 5 of nuclear genes Prolactin (Prl) and Ribosomal Protein L3 (RPL3). The analyses contain 358 specimens of B. xanthellus from 39 localities distributed throughout its range. The number of genetically diverged groups was estimated using Bayesian inference on Cyt b haplotypes. Haplotype networks, AMOVA and pairwise fixation index was used to evaluate population structure and gene flow. Historical demography was inferred through neutrality tests and the Extended Bayesian Skyline Plot (EBSP) method. Five longitudinally distributed Cyt b haplogroups for B. xanthellus were identified in the Xingu River and its major tributaries, the Bacajá and Iriri. The demographic analysis suggests that rapids habitats have expanded in the Iriri and Lower Xingu rivers since 200 ka (thousand years) ago. This expansion is possibly related to an increase in water discharge as a consequence of higher rainfall across eastern Amazonia. Conversely, this climate shift also would have promoted zones of sediment trapping and reduction of rocky habitats in the Xingu River channel upstream of the Iriri River mouth. Populations of B. xanthellus showed strong genetic structure along the free-flowing river channels of the Xingu and its major tributaries, the Bacajá and Iriri. The recent impoundment of the Middle Xingu channel for the Belo Monte hydroelectric dam may isolate populations at the downstream limit of the species distribution. Therefore, future conservation plans must consider the genetic diversity of B. xanthellus throughout its range.

Diversity of Loricariidae (Actinopterygii: Siluriformes) assemblages in two Conservation Areas of the Middle Xingu River, Brazilian Amazon, and their suitability for sustainable ornamental fisheries

The Xingu River has one of the most diverse fish faunas in the Amazon region. Loricariidae stands out as the most diverse family in the basin, comprising more than 60 species distributed over 26 genera. Species of Loricariidae are some of the most economically valued in the ornamental market worldwide. The loss of fishing environments in Altamira region due to dam impacts is driving a shift of ornamental fishing to areas upstream, among which are included the Xingu River and Iriri River Extractive Reserve Areas. Thus, the objective of this work was to inventory fish species with ornamental potential in these extractive reserves to serve as a baseline to help guide the future management of ornamental fishing in those areas. Thirty-two species of Loricariidae were collected in these reserves through either free diving or diving with compressed air. The composition of species varied according to the sampling method and area. The majority of species found in the reserves are also found in the impacted areas of Belo Monte near Altamira. The study areas showed high diversity of fish species in rapids environments, suggesting that this area could serve as an additional source of income for the residents of these reserves.(AU)

O rio Xingu possui umas das mais diversas ictiofaunas da região Amazônica. Loricariidae destaca-se como a família mais diversa nessa bacia, compreendendo mais de 60 espécies distribuídas em 26 gêneros. As espécies de Loricariidae estão entre as mais valorizadas economicamente no mercado ornamental mundial. A perda de ambientes de pesca na região de Altamira devido aos impactos das barragens está provocando uma mudança da pesca ornamental para áreas a montante, entre as quais estão incluídas as áreas das Reservas Extrativistas do Rio Xingu e do Rio Iriri. Assim, o objetivo deste trabalho foi o de inventariar espécies de peixes com potencial ornamental nestas reservas extrativistas para servir de linha de base para ajudar a orientar o gerenciamento futuro da pesca ornamental nestas áreas. Trinta e duas espécies de Loricariidae foram coletadas nestas reservas através de mergulho livre ou mergulho com ar comprimido. A composição das espécies variou de acordo com o método de amostragem e a área de conservação. A maioria das espécies encontradas nas reservas também são encontradas nas áreas impactadas de Belo Monte, perto de Altamira. As áreas de estudo mostraram grande diversidade de espécies de peixes em ambientes rápidos, sugerindo que esta área poderia servir como uma fonte adicional de renda para os residentes destas reservas.(AU)

Karyotypic Evolution and Chromosomal Organization of Repetitive DNA Sequences in Species of Panaque, Panaqolus, and Scobinancistrus (Siluriformes and Loricariidae) from the Amazon Basin.

Loricariidae family comprises the greatest variability of Neotropical catfish species, with more than 800 valid species. This family shows significant chromosomal diversity. Mapping of repetitive DNA sequences can be very useful in exploring such diversity, especially among groups that appear to share a preserved karyotypic macrostructure. We describe the karyotypes of Panaque armbrusteri and Panaqolus sp., as assessed using classical cytogenetic methods. Moreover, we offer a map of their repetitive sequences, including 18S and 5S ribosomal DNAs, the Rex1 and Rex3 retrotransposons, and the Tc1-mariner transposon in P. armbrusteri, Panaqolus sp., Scobinancistrus aureatus, and Scobinancistrus pariolispos. Those species share chromosome numbers of 2n = 52, but are divergent in their chromosome structures and the distributions of their repetitive DNA sequences. In situ hybridization with 18S and 5S rDNA probes confirms chromosome location in different pairs; in Panaqolus sp. these sites are in synteny. This multigene family organization can be explained by the occurrence of chromosome rearrangements, and possible events, such as transposition and unequal crossing-over. Rex1 and Rex3 retrotransposons and the Tc1-mariner transposon appeared predominantly dispersed and in small clusters in some chromosome regions. These data emphasize the importance of repetitive sequences in promoting the karyotypic evolution of these species.

Integrated Cytogenetic and Mitochondrial DNA Analyses Indicate That Two Different Phenotypes of Hypancistrus (L066 and L333) Belong to the Same Species.

The diversity of Hypancistrus species in the Xingu River is remarkable and the variation in color morphs represents a real challenge to taxonomists to delimit species boundaries. One of the most recognizable Hypancistrus complexes is the worm-lined species, known in the aquarium trade as King Tiger Plec in English, Hypancistrus "pão" in Portuguese or under the L-numbers L066 and L333 that represent two melanic pigment pattern phenotypes. To assess the identity of these two phenotypes, we described their karyotypes and sequenced part of the mitochondrial cytochrome oxidase I gene (DNA barcode). These fishes have 52 chromosomes (40 meta-submetacentric and 12 subtelo-acrocentric) and a strong heteromorphism in chromosome pair 21 was observed, which does not correlate with the two phenotypes or sex. DNA barcodes separated the samples analyzed from Hypancistrus zebra and other publicly available sequences of Loricariidae showing no divergence between the two phenotypes. The data set indicates that worm-lined Hypancistrus from the Xingu form a single species with clear chromosomal and melanic pigment pattern polymorphisms.