The 5S rDNA in two Abracris grasshoppers (Ommatolampidinae: Acrididae): molecular and chromosomal organization.

The 5S ribosomal DNA (rDNA) sequences are subject of dynamic evolution at chromosomal and molecular levels, evolving through concerted and/or birth-and-death fashion. Among grasshoppers, the chromosomal location for this sequence was established for some species, but little molecular information was obtained to infer evolutionary patterns. Here, we integrated data from chromosomal and nucleotide sequence analysis for 5S rDNA in two Abracris species aiming to identify evolutionary dynamics. For both species, two arrays were identified, a larger sequence (named type-I) that consisted of the entire 5S rDNA gene plus NTS (non-transcribed spacer) and a smaller (named type-II) with truncated 5S rDNA gene plus short NTS that was considered a pseudogene. For type-I sequences, the gene corresponding region contained the internal control region and poly-T motif and the NTS presented partial transposable elements. Between the species, nucleotide differences for type-I were noticed, while type-II was identical, suggesting pseudogenization in a common ancestor. At chromosomal point to view, the type-II was placed in one bivalent, while type-I occurred in multiple copies in distinct chromosomes. In Abracris, the evolution of 5S rDNA was apparently influenced by the chromosomal distribution of clusters (single or multiple location), resulting in a mixed mechanism integrating concerted and birth-and-death evolution depending on the unit.

DNA barcode of parodontidae species from the La Plata river basin - applying new data to clarify taxonomic problems

In the past years, DNA barcoding has emerged as a quick, accurate and efficient tool to identify species. Considering the difficulty in identifying some Parodontidae species from the La Plata basin and the absence of molecular data for the group, we aimed to test the effectiveness of DNA barcoding and discuss the importance of using different approaches to solve taxonomic problems. Eight species were analyzed with partial sequences of Cytochrome c oxidase I. The mean intraspecific K2P genetic distance was 0.04% compared to 4.2% for mean interspecific K2P genetic distance. The analyses of distance showed two pairs of species with K2P genetic divergence lower than 2%, but enough to separate these species. Apareiodon sp. and A. ibitiensis, considered as the same species by some authors, showed 4.2% genetic divergence, reinforcing their are different species. Samples of A. affinis from the Uruguay and Paraguay rivers presented 0.3% genetic divergence, indicating a close relationship between them. However, these samples diverged 6.1% from the samples of the upper Paraná River, indicating that the latter represents a potentially new species. The results showed the effectiveness of the DNA barcoding method in identifying the analyzed species, which, together with the morphological and cytogenetic available data, help species identification.

Nos últimos anos o DNA barcoding surgiu como uma ferramenta rápida, precisa e eficiente para identificar espécies. Considerando a dificuldade na identificação de algumas espécies de Parodontidae da bacia do rio da Prata e da ausência de dados moleculares para o grupo, testamos a eficácia do código de barras de DNA e discutimos a importância do uso de diferentes abordagens para resolver problemas taxonômicos. Oito espécies foram analisadas com sequencias parciais do gene citocromo c oxidase I. A distância genética média K2P intraespecífica foi de 0,04% comparado com 4,2% para distância genética média K2P interespecífica. As análises de distância mostraram dois pares de espécies com divergência genética K2P inferior a 2%, mas o suficiente para separar estas espécies. Apareiodon sp. e A. ibitiensis, consideradas a mesma espécie por alguns autores, mostraram 4,2% de divergência genética, confirmando serem espécies diferentes. Amostras de A. affinis dos rios Uruguai e Paraguai apresentaram 0,3% de divergência genética, indicando um maior grau de relação entre elas, no entanto, esses exemplares divergiram em 6,1% em relação aos exemplares do alto rio Paraná, o que indica que estes últimos representam uma espécie potencialmente nova. Os resultados mostraram a eficácia do método de DNA barcoding na identificação das espécies analisadas, os quais, em conjunto com os dados morfológicos e citogenéticos disponíveis auxiliam na identificação inequívoca das espécies.

A new miniature characid (Ostariophysi: Characiformes: Characidae), with phylogenetic position inferred from morphological and molecular data.

Erythrocharax altipinnis is described from the Serra do Cachimbo, Pará, Brazil. The new taxon is distinguished from all of the Characidae genera by having the pelvic bones firmly attached through the isquiatic processes; a nearly triangular hiatus in the musculature covering the anterior chamber of the swim bladder between the first and second pleural ribs (pseudotympanum); the pedunculate, notably expanded and distally compressed teeth in both jaws; circumorbital series represented by antorbital and four infraorbital bones with laterosensory canals not enclosed; a single tooth row in the premaxillary with the teeth perfectly aligned and similar in shape and cusp number; the first three branched dorsal-fin rays distinctly elongate in males; a bright red adipose and caudal fins in life; a conspicuous dark midlateral stripe extending from the opercle to the tip of the median caudal-fin rays; and by the absence of a humeral spot. The phylogenetic position of the new taxon is discussed using morphological and molecular datasets, with conflicting results of both approaches discussed. Additionally, a summarized discussion on the current problems in the Characidae taxonomy is presented and the principal biases in the morphological dataset are also discussed.

DNA barcodes identify marine fishes of São Paulo State, Brazil.

Anthropogenic impacts are an increasing threat to the diversity of fishes, especially in areas around large urban centres, and many effective conservation actions depend on accurate species identification. Considering the utility of DNA barcoding as a global system for species identification and discovery, this study aims to assemble a DNA barcode reference sequence library for marine fishes from the coastal region of São Paulo State, Brazil. The standard 652 bp 'barcode' fragment of the cytochrome c oxidase subunit I (COI) gene was PCR amplified and bidirectionally sequenced from 678 individuals belonging to 135 species. A neighbour-joining analysis revealed that this approach can unambiguously discriminate 97% of the species surveyed. Most species exhibited low intraspecific genetic distances (0.31%), about 43-fold less than the distance among species within a genus. Four species showed higher intraspecific divergences ranging from 2.2% to 7.6%, suggesting overlooked diversity. Notably, just one species-pair exhibited barcode divergences of <1%. This library is a first step to better know the molecular diversity of marine fish species from São Paulo, providing a basis for further studies of this fauna - extending the ability to identify these species from all life stages and even fragmentary remains, setting the stage for a better understanding of interactions among species, calibrating the estimations about species composition and richness in an ecosystem, and providing tools for authenticating bioproducts and monitoring illegal species exploitation.