Toe pad morphology and adhesion in the miniaturized gecko, Chatogekko amazonicus (Gekkota: Sphaerodactylidae).

Chatogekko amazonicus is a miniaturized gecko from northern South America and is among the smallest of toe pad bearing lizards. The toe pads of C. amazonicus are miniscule, between 18% and 27% of the plantar surface area.

First Karyotypic Insights into Potamotrygon schroederi Fernández-Yépez, 1958: Association of Different Classes of Repetitive DNA.

Introduction: Currently, there are 38 valid species of freshwater stingrays, and these belong to the subfamily Potamotrygoninae. However, cytogenetic information about this group is limited, with studies mainly using classical techniques, Giemsa, and C-banding.

Methods: In this study, we used classical and molecular cytogenetic techniques - mapping of 18S and 5S rDNA and simple sequence repeats (SSRs) - in order to investigate the karyotypic composition of Potamotrygon schroederi and reveal the karyoevolutionary trends of this group.

Karyotypic characterization of Centromochlus schultzi Rössel 1962 (Auchenipteridae, Centromochlinae) from the Xingu River basin: New inferences on chromosomal evolution in Centromochlus.

Centromochlinae is a widely diverse subfamily with more than 50 species and several taxonomic conflicts due to morphological similarity between Tatia and Centromochlus species. However, cytogenetic studies on this group have been limited to only four species so far. Therefore, here we present the karyotype of Centromochlus schultzi from the Xingu River in Brazil using classic cytogenetic techniques, physical mapping of the 5S and 18S rDNAs, and telomeric sequences (TTAGGG)n.

Karyotypic variation of two populations of the small freshwater stingray Potamotrygon wallacei Carvalho, Rosa & Araújo 2016: A classical and molecular approach.

Potamotrygoninae comprises a group of Neotropical fishes with an ancient relationship with marine environments. In the last few years, 11 new Potamotrygon species were described, including Potamotrygon wallacei Carvalho, Araújo e Rosa 2016. Cytogenetic data about this species are limited to classical markers (Giemsa, C-Banding and Ag-NOR techniques), these studies highlighted a rare sexual chromosome system XX/X0 with males presenting 67 chromosomes and females 68 chromosomes.

Chromosomal rearrangements and the first indication of an ♀X X X X /♂X X Y sex chromosome system in Rineloricaria fishes (Teleostei: Siluriformes).

Rineloricaria is the most diverse genus within the freshwater fish subfamily Loricariinae, and it is widely distributed in the Neotropical region. Despite limited cytogenetic data, records from southern and south-eastern Brazil suggest a high rate of chromosomal rearrangements in this genus, mirrored in remarkable inter- and intraspecific karyotype variability. In the present work, we investigated the karyotype features of Rineloricaria teffeana, an endemic representative from northern Brazil, using both conventional and molecular cytogenetic techniques.

Karyotype variability in six Amazonian species of the family Curimatidae (Characiformes) revealed by repetitive sequence mapping.

Fishes of the Curimatidae family represent one of the most important freshwater ichthyofauna groups of Central and South America, with 117 recognized species distributed in eight genera. In this study, six species - Curimata inornata, Curimatella dorsalis, and Psectrogaster falcata collected from the Lower Araguaia River, Pará, Brazil; Curimata vittata, Curimatella meyeri, and Psectrogaster rutiloides collected from the Catalão Lake, Amazonas, Brazil - were cytogenetically analyzed, investigate the occurrence and distribution of repetitive DNA classes in the karyotypes. All species had 2n=54 metacentric/submetacentric chromosomes.

The Genetic Differentiation of (Teleostei, Characiformes) Species is Likely Influenced by Both Geographical Distribution and Chromosomal Rearrangements.

Allopatry is generally considered to be one of the main contributors to the remarkable Neotropical biodiversity. However, the role of chromosomal rearrangements including neo-sex chromosomes for genetic diversity is still poorly investigated and understood. Here, we assess the genetic divergence in five species using population genomics and combined the results with previously obtained cytogenetic data, highlighting that molecular genetic diversity is consistent with their chromosomal features.

Matamatas Chelus spp. (Testudines, Chelidae) have a remarkable evolutionary history of sex chromosomes with a long-term stable XY microchromosome system.

The genus Chelus, commonly known as Matamata is one of the most emblematic and remarkable species among the Neotropical chelids. It is an Amazonian species with an extensive distribution throughout Negro/Orinoco and Amazonas River basins. Currently, two species are formally recognized: Chelus orinocensis and Chelus fimbriata and although it is still classified as "Least Concern" in the IUCN, the Matamatas are very appreciated and illegally sold in the international pet trade.

Against the mainstream: exceptional evolutionary stability of ZW sex chromosomes across the fish families Triportheidae and Gasteropelecidae (Teleostei: Characiformes).

Teleost fishes exhibit a breath-taking diversity of sex determination and differentiation mechanisms. They encompass at least nine sex chromosome systems with often low degree of differentiation, high rate of inter- and intra-specific variability, and frequent turnovers. Nevertheless, several mainly female heterogametic systems at an advanced stage of genetic differentiation and high evolutionary stability have been also found across teleosts, especially among Neotropical characiforms.

Tracking the Evolutionary Trends Among Small-Size Fishes of the Genus (Characiforme, Lebiasinidae): New Insights From a Molecular Cytogenetic Perspective.

Miniature fishes have always been a challenge for cytogenetic studies due to the difficulty in obtaining chromosomal preparations, making them virtually unexplored. An example of this scenario relies on members of the family Lebiasinidae which include miniature to medium-sized, poorly known species, until very recently. The present study is part of undergoing major cytogenetic advances seeking to elucidate the evolutionary history of lebiasinids.

Adding New Pieces to the Puzzle of Karyotype Evolution in (Siluriformes, Loricariidae): Investigation of Amazonian Species.

A remarkable morphological diversity and karyotype variability can be observed in the Neotropical armored catfish genus . These fishes offer a useful model to explore both the evolution of karyotypes and sex chromosomes, since many species possess male-heterogametic sex chromosome systems and a high rate of karyotype repatterning. Based on the karyotype organization, the chromosomal distribution of several repetitive DNA classes, and the rough estimates of genomic divergences at the intraspecific and interspecific levels via Comparative Genomic Hybridization, we identified shared diploid chromosome numbers (2n = 54) but different karyotype compositions in (20m + 26sm + 8a) and sp.

Revisiting the Karyotypes of Alligators and Caimans (Crocodylia, Alligatoridae) after a Half-Century Delay: Bridging the Gap in the Chromosomal Evolution of Reptiles.

Although crocodilians have attracted enormous attention in other research fields, from the cytogenetic point of view, this group remains understudied. Here, we analyzed the karyotypes of eight species formally described from the Alligatoridae family using differential staining, fluorescence in situ hybridization with rDNA and repetitive motifs as a probe, whole chromosome painting (WCP), and comparative genome hybridization. All Caimaninae species have a diploid chromosome number (2n) 42 and karyotypes dominated by acrocentric chromosomes, in contrast to both species of Alligatorinae, which have 2n = 32 and karyotypes that are predominantly metacentric, suggesting fusion/fission rearrangements.

: Current Knowledge on Natural History, Medical Importance, and Clinical Toxinology.

is a rattlesnake subspecies mainly found in Roraima, the northernmost state of Brazil. Envenomings caused by this subspecies lead to severe clinical manifestations (e.g.

Cytogenetic Analysis of Panaqolus tankei Cramer & Sousa, 2016 (Siluriformes, Loricariidae), an Ornamental Fish Endemic to Xingu River, Brazil.

Despite conservation of the diploid number, a huge diversity in karyotype formulae is found in the Ancistrini tribe (Loricariidae, Hypostominae). However, the lack of cytogenetic data for many groups impairs a comprehensive understanding of the chromosomal relationships and the impact of chromosomal changes on their evolutionary history. Here, we present for the first time the karyotype of Panaqolus tankei Cramer & Sousa, 2016.

Looking for genetic effects of polluted anthropized environments on Caiman crocodilus crocodilus (Reptilia, Crocodylia): A comparative genotoxic and chromosomal analysis.

The Amazon aquatic ecosystems have been modified by the human population growth, going through changes in their water bodies and aquatic biota. The spectacled alligator (Caiman crocodilus crocodilus) has a wide distribution and adaptability to several environments, even those polluted ones. This study aimed to investigate if a Caiman species living in urban streams of Manaus city (Amazonas State, Brazil) is affected by environmental pollution.

Chromosomal Evolution in Aspredinidae (Teleostei, Siluriformes): Insights on Intra- and Interspecific Relationships with Related Groups.

The family Aspredinidae comprises a clade of complex systematic relationships, both from molecular and morphological approaches. In this study, conventional and molecular cytogenetic studies coupled with nucleotide sequencing were performed in 6 Aspredininae species (Amaralia hypsiura, Bunocephalus cf. aloikae, Bunocephalus amaurus, Bunocephalus aff.

Revisiting the Karyotype Evolution of Neotropical Boid Snakes: A Puzzle Mediated by Chromosomal Fissions.

The Boidae family is an ancient group of snakes widely distributed across the Neotropical region, where several biogeographic events contributed towards shaping their evolution and diversification. Most species of this family have a diploid number composed of 2n = 36; however, among Booidea families, the Boidae stands out by presenting the greatest chromosomal diversity, with 2n ranging between 36 and 44 chromosomes and an undifferentiated XY sex chromosome system. Here, we applied a comparative chromosome analysis using cross-species chromosome paintings in five species representing four Boidae genera, to decipher the evolutionary dynamics of some chromosomes in these Neotropical snakes.

Comparative cytogenetic of six species of Amazonian Peacock bass (, Cichlinae): intrachromosomal variations and genetic introgression among sympatric species.

Cytogenetic data for the genus Bloch et Schneider, 1801 are still very limited, with only four karyotype descriptions to date. The sum of the available cytogenetic information for species, points to a maintenance of the diploid number of 48 acrocentric chromosomes, considered a typical ancestral feature in cichlids. In the current study, we performed molecular and classical cytogenetic analyses of the karyotype organization of six species of , the earliest-diverging genus of Neotropical cichlids.

The Amazonian Red Side-Necked Turtle (Spix, 1824) (Testudines, Chelidae) Has a GSD Sex-Determining Mechanism with an Ancient XY Sex Microchromosome System.

The Amazonian red side-necked turtle is an endemic Amazonian Chelidae species that occurs in small streams throughout Colombia and Brazil river basins. Little is known about various biological aspects of this species, including its sex determination strategies. Among chelids, the greatest karyotype diversity is found in the Neotropical species, with several 2 configurations, including cases of triploidy.

Landscape of snake' sex chromosomes evolution spanning 85 MYR reveals ancestry of sequences despite distinct evolutionary trajectories.

Most of snakes exhibit a ZZ/ZW sex chromosome system, with different stages of degeneration. However, undifferentiated sex chromosomes and unique Y sex-linked markers, suggest that an XY system has also evolved in ancestral lineages. Comparative cytogenetic mappings revealed that several genes share ancestry among X, Y and Z chromosomes, implying that XY and ZW may have undergone transitions during serpent's evolution.

Centric Fusions behind the Karyotype Evolution of Neotropical Pencilfishes (Characiforme, Lebiasinidae): First Insights from a Molecular Cytogenetic Perspective.

Lebiasinidae is a Neotropical freshwater family widely distributed throughout South and Central America. Due to their often very small body size, Lebiasinidae species are cytogenetically challenging and hence largely underexplored. However, the available but limited karyotype data already suggested a high interspecific variability in the diploid chromosome number (2), which is pronounced in the speciose genus , a popular taxon in ornamental fish trade due to its remarkable body coloration.

Cytogenetics of the small-sized fish, Copeina guttata (Characiformes, Lebiasinidae): Novel insights into the karyotype differentiation of the family.

Lebiasinidae is a small fish family composed by miniature to small-sized fishes with few cytogenetic data (most of them limited to descriptions of diploid chromosome numbers), thus preventing any evolutionary comparative studies at the chromosomal level. In the present study, we are providing, the first cytogenetic data for the red spotted tetra, Copeina guttata, including the standard karyotype, C-banding, repetitive DNA mapping by fluorescence in situ hybridization (FISH) and comparative genomic hybridization (CGH), providing chromosomal patterns and novel insights into the karyotype differentiation of the family. Males and females share diploid chromosome number 2n = 42 and karyotype composed of 2 metacentric (m), 4 submetacentric (sm) and 36 subtelocentric to acrocentric (st-a) chromosomes.

Interspecific Genetic Differences and Historical Demography in South American Arowanas (Osteoglossiformes, Osteoglossidae, ).

The South American arowanas (Osteoglossiformes, Osteoglossidae, ) are emblematic species widely distributed in the Amazon and surrounding basins. Arowana species are under strong anthropogenic pressure as they are extensively exploited for ornamental and food purposes. Until now, limited genetic and cytogenetic information has been available, with only a few studies reporting to their genetic diversity and population structure.

Comparative Cytogenetics and Neo-Y Formation in Small-Sized Fish Species of the Genus Pyrrhulina (Characiformes, Lebiasinidae).

Although fishes have traditionally been the subject of comparative evolutionary studies, few reports have concentrated on the application of multipronged modern molecular cytogenetic techniques (such as comparative genomic hybridization = CGH and whole chromosome painting = WCP) to analyze deeper the karyotype evolution of specific groups, especially the historically neglected small-sized ones. Representatives of the family Lebiasinidae (Characiformes) are a notable example, where only a few cytogenetic investigations have been conducted thus far. Here, we aim to elucidate the evolutionary processes behind the karyotype differentiation of species on a finer-scale cytogenetic level.