Chromosomal Mapping of the Histone Multigene Family and U2 snRNA in Hypancistrus Species (Siluriformes, Loricariidae) from the Brazilian Amazon.

Loricariidae (Siluriformes) comprises ∼1026 species of neotropical fish, being considered the most diverse among the Siluriformes. Studies on repetitive DNA sequences have provided important data on the evolution of the genomes of members of this family, especially of the Hypostominae subfamily. In this study, the chromosomal mapping of the histone multigene family and U2 snRNA was performed in two species belonging to the Hypancistrus genus, Hypancistrus sp. "pão" (2n = 52, 22m + 18sm +12st) and Hypancistrus zebra (2n = 52, 16m + 20sm +16st). The presence of dispersed signals of histones H2A, H2B, H3, and H4 in the karyotype of both species, with each sequence displaying a varied level of accumulation and dispersion of these sequences between them was observed; in addition, U2 snDNA probe only showed positive results in H. zebra, which present this multigene in the terminal region of three chromosomal pairs. The obtained results resemble data already analyzed in the literature, in which the action of transposable elements interfere in the organization of these multigene families, in addition to other evolutionary processes that shape the evolution of the genome, such as circular or ectopic recombination. This study also shows that the dispersion of the multigene histone family is quite complex, and from this, these data serve as a point of discussion for the evolutionary processes that occur in the Hypancistrus karyotype.

Fishway in hydropower dams: a scientometric analysis.

Building dams for hydroelectric use causes several negative effects on the aquatic fauna with special attention to fish communities. In fact, among other impacts, dams act as a barrier for migratory fish, causing discontinuities in rivers and not allowing fish to move to the headwaters to breed and back to the lower portions of rivers, to grow. For more than 300 years, fishways have been used to minimize the impact of dams. Here, we assess the worldwide knowledge about fishways, identifying the temporal and spatial pattern and the situation of Brazil in this global pattern. For this, we conducted scientometric research on the Web of Science repository with the following words: weir, fish, facilities, ladder, pass, dam, fish ladder, fish pass, fishway, hydropower, Petromyzon, and salmon between 1985 and 2019. Initially, we obtained 1282 articles. After a selection, 324 articles aimed to describe fishway efficiency and the relationship with the fish fauna remained. Most of the articles on dams, fishways, and fish are from North America and Europe. Among the articles in South America, most are from Brazil. Nonetheless, information on the topic is incipient in Brazil, since the country has one of the biggest hydropower in the world and 42 scientific articles about fishways published in the international scientific database. Ecology is the area of knowledge with most articles, with continuous growth in the last 10 years. Studies in the field of ecology are strategical, as this field can integrate different areas of knowledge to test the efficiency of fishways in fish conservation and may be able to answer the question: "Are fishways an ecological trap?" Research focusing on this question is important to understand the efficiency of fishways to better evaluate solutions to minimize the negative effects of dams on fish and increase the effectiveness of fishways.

In Situ Localization of Ribosomal Sites in Peckoltia and Ancistomus (Loricariidae: Hypostominae) from the Amazon Basin.

Loricariidae is a diverse group of fish from the neotropical region, occupying a wide variety of freshwater environments. Cytogenetic data have brought important insights into Loricariidae diversity because they help validate undescribed species as well as our understanding of inter- and intraspecific diversity. However, conventional cytogenetic approaches are limited in their ability to detect variability in some lineages, as seen in the Peckoltia clade, owing to their apparent conserved karyotype. Thus, the aim of this work was to map 5S and 18S ribosomal (rDNA) sites in five species of Peckoltia and one species of Ancistomus from the Amazon basin, and discusses the mechanisms of organization and diversification of these clusters. The species analyzed were found to have 2n = 52 and share KF = 38 m-sm +14st-a chromosomes, except Peckoltia vittata with KF = 34 m-sm +18st-a. Extensive variations in the number and location of 5S and 18S rDNA sites were observed among species. These data indicate that inversions are not the most important events in karyotype evolution in this group, and should prove useful in identifying the species studied here. In addition to inversions, transpositions are important evolutionary events that are involved at least in rDNA clusters spreading in Peckoltia and probably in other species of Hypostominae.

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.