Abstract Epinephelidae (groupers) is an astonishingly diverse group of carnivorous fish widely distributed in reef environments around the world, with growing economic importance. The first chromosomal inferences suggested a conservative scenario for the family. However, to date, this has not been validated using biogeographic and phylogenetic approaches. Thus, to estimate karyotype diversification among groupers, eight species from the Atlantic and Indian oceans were investigated using conventional cytogenetic protocols and fluorescence in situ hybridization of repetitive sequences (rDNA, microsatellites, transposable elements). Despite the remarkable persistence of some symplesiomorphic karyotype patterns, such as all species sharing 2n=48 and most preserve a basal karyotype (2n=48 acrocentrics), the chromosomal diversification in the family revealed an unsuspected evolutionary dynamic, where about 40% of the species escape from the ancestral karyotype pattern. These karyotype changes showed a relation with the historical biogeography, likely as a byproduct of the progressive occupancy of new areas (huge diversity of adaptive and speciation conditions). In this context, oceanic regions harboring more recent clades such as those of the Indo-Pacific, exhibited a higher karyotype diversity. Therefore, the karyotype evolution of Epinephelidae fits well with the expansion and geographic contingencies of its clades, providing a more complex and diverse scenario than previously assumed.

Resumo Alguns peixes pelágicos de grande porte são alvos preferenciais para a pesca esportiva e comercial. Apesar de sua importância econômica, os dados citogenéticos sobre seus processos evolutivos e de manejo são muito deficientes, principalmente devido às dificuldades logísticas. Aqui são apresentadas informações cromossômicas de duas espécies carismáticas, o tarpão, Megalops atlanticus (Elopiformes: Megalopidae), e o agulhão-vela, Istiophorus platypterus (Istiophoriformes: Istiophoridae), ambos com ampla distribuição no oceano Atlântico. Os dados citogenéticos foram obtidos usando métodos convencionais (coloração em Giemsa, técnica de Ag-NORs e bandamento C), coloração com fluorocromos específicos e hibridização fluorescente in situ (FISH) com sondas DNAr. Megalops atlanticus possui 2n = 50 cromossomos, todos acrocêntricos (NF = 50), enquanto Istiophorus platypterus possui 2n = 48 cromossomos, 2m + 2st + 44a (NF = 52). Populações de M. atlanticus do Atlântico Sul e Caribe compartilham padrões cariotípicos idênticos, provavelmente associados ao fluxo gênico entre regiões. Por sua vez, I. platypterus apresenta semelhanças cariotípicas micro e macroestruturais com grupos filogeneticamente próximos, como Carangidae. As características cromossômicas destas espécies destacam seus caminhos evolutivos independentes. Adicionalmente, os dados apresentados contribuem com novos aspectos da fauna pelágica e apoiarão futuros estudos comparativos com espécies congenéricas, esclarecendo as tendências evolutivas do cariótipo destes grupos de peixes.

Abstract Some pelagic and usually large sized fishes are preferential targets for sport and commercial fishing. Despite their economic importance, cytogenetic data on their evolutionary processes and management are very deficient, especially due to logistical difficulties. Here, information for two of such charismatic species, the tarpon, Megalops atlanticus (Elopiformes: Megalopidae), and the sailfish, Istiophorus platypterus (Istiophoriformes: Istiophoridae), both with a wide Atlantic distribution, were provided. Cytogenetic data were obtained using conventional methods (Giemsa staining, Ag-NORs technique, and C-banding), base-specific fluorochrome staining and fluorescence in situ hybridization (FISH) with rDNA probes. Megalops atlanticus has 2n = 50 chromosomes, all acrocentric ones (NF = 50), while Istiophorus platypterus has 2n = 48 chromosomes, 2m + 2st + 44a (NF = 52). Megalops atlanticus populations from the South Atlantic and Caribbean share identical karyotypic patterns, likely associated with gene flow between them. In turn, I. platypterus presents karyotype similarities with phylogenetically close groups, such as Carangidae. The chromosomal characteristics of these species highlight their independent evolutionary paths. Additionally, the current data contribute to knowledge of new aspects of pelagic fish fauna and will support further comparative studies with congeneric species, clarifying evolutionary karyotype trends of these fish groups.

Abstract The freshwater family Siluridae occurs in Eurasia and is especially speciose in South and Southeast Asia, representing an important aquaculture and fishery targets. However, despite the restricted cytogenetic data, a high diploid number variation (from 2n=40 to 92) characterizes this fish group. Considering the large genomic divergence among its species, silurid genomes have experienced an enormous diversification throughout their evolutionary history. Here, we aim to investigate the chromosomal distribution of several microsatellite repeats in 12 Siluridae species and infer about their possible roles in the karyotype evolution that occurred in this group. Our results indicate divergent patterns of microsatellite distribution and accumulation among the analyzed species. Indeed, they are especially present in significant chromosome locations, such as the centromeric and telomeric regions, precisely the ones associated with several kinds of chromosomal rearrangements. Our data provide pieces of evidence that repetitive DNAs played a direct role in fostering the chromosomal differentiation and biodiversity in this fish family.

Cattleya granulosa é uma orquídea ameaçada de extinção endêmica da região litorânea do Nordeste do Brasil. Este estudo teve como objetivos avaliar os níveis de agregação espacial em uma população preservada da espécie, em uma área de 4.225 m2 da unidade de conservação do Parque das Dunas, em Natal, RN. Além de caracterizar o hábito de vida da população, foi utilizada a função de segunda ordem da densidade de vizinhos (NDF) para determinar o padrão espacial nas classes de distância, com o uso do programa SpPack. Quanto ao hábito de vida, 73% das plantas eram epífitas (N = 136) e 27% terrestres (N = 50). As epífitas têm especificidade com um único forófito, indivíduos arbóreos de Eugenia spp. (Myrtaceae). C. granulosa possui padrão espacial agregado, com maior densidade de vizinhos (NDF) no raio de até 5 m. Esses dados sugerem um potencial dispersivo restrito e com influência direta sobre ações de conservação biológica da espécie.

Cattleya granulosa is an endemic and endangered orchid species of the coastal region of northeastern Brazil. This study aimed to evaluate the levels of spatial aggregation in a preserved population, in an area of 4.225 m2 of the conservation unit of ‘Parque das Dunas’ Natal, Rio Grande do Norte state, Brazil. We evaluated the life form of the population as well as its neighborhood density factor (NDF) to determine the spatial distribution in distance classes, using the SpPack software program. Regarding the life form, 73% of the plants (N = 136) were epiphyte and 27% were terrestrial (N = 50). The epiphytes present specificity with a single host tree, Eugenia spp. (Myrtaceae). The spatial pattern of Cattleya granulosa is aggregated, with the highest density of neighbors (NDF) within a radius of 5 m. These data suggest restricted dispersion with direct influence on actions for conservation of the species.

O objetivo deste trabalho foi estimar o nível e a distribuição da variabilidade genética em reprodutores brasileiros do camarão marinho (Litopenaeus vannamei). Nove dos maiores laboratórios de maturação do país foram analisados por meio de marcadores microssatélites codominantes e altamente polimórficos. Os resultados obtidos a partir da genotipagem de dez locos de microssatélites são indicativos de variabilidade genética compatível com aquela encontrada em populações naturais de L. vannamei no México e na América Central. Uma possível explicação é a origem altamente diversificada e relativamente recente dos plantéis disponíveis. A análise bayesiana detectou sinal correspondente a cinco populações originais. A distribuição das distâncias genéticas reflete parcialmente a localização geográfica, e essa informação será útil na formação de novos plantéis. Portanto, a variabilidade genética de L. vannamei entre nove dos maiores laboratórios de maturação nacionais pode ser considerada alta.

The objective of this work was to estimate the genetic variability level and distribution in Brazilian broodstocks of marine shrimp (Litopenaeus vannamei). Nine of the country's largest hatcheries were evaluated using codominant and highly polymorphic microsatellite markers. The results obtained from genotyping of ten microsatellite loci are indicative of genetic variability that is compatible with that found in wild populations of L. vannamei in Mexico and Central America. A possible explanation is the highly diversified and relatively recent origin of the available broodstocks. Bayesian analysis detected a signal for five founding populations. The distribution of genetic distances partially reflects geographical location, and this information will be useful for the creation of new broodstocks. Therefore, L. vannamei genetic variability among nine of the largest national hatcheries can be considered high.

The order Anguilliformes comprises 15 families, 141 genera and 791 fish species. Eight families had at least one karyotyped species, with a prevalence of 2n = 38 chromosomes and high fundamental numbers (FN). The only exception to this pattern is the family Muraenidae, in which the eight species analyzed presented 2n = 42 chromosomes. Despite of the large number of Anguilliformes species, karyotypic reports are available for only a few representatives. In the present work, a species of Ophichthidae, Myrichthys ocellatus (2n = 38; 8m+14sm+10st+6a; FN = 70) and four species of Muraenidae, Enchelycore nigricans (2n = 42; 6m+8sm+12st+16a; FN = 68), Gymnothorax miliaris (2n = 42; 14m+18sm+10st; FN = 84), G. vicinus (2n = 42; 8m+6sm+28a; FN = 56) and Muraena pavonina (2n = 42; 6m+4sm+32a; FN = 52), collected along the Northeastern coast of Brazil and around the St Peter and St Paul Archipelago were analyzed. Typical large metacentric chromosomes were observed in all species. Conspicuous polymorphic heterochromatic regions were observed at the centromeres of most chromosomes and at single ribosomal sites. The data obtained for Ophichthidae corroborate the hypothesis of a karyotypic diversification mainly due to pericentric inversions and Robertsonian rearrangements, while the identification of constant chromosome numbers in Muraenidae (2n = 42) suggests a karyotype diversification through pericentric inversions and heterochromatin processes.

The Lutjanidae or snappers are a family of perciform fishes, mainly marine but with some members living in estuaries and entering fresh water to feed. Some are important food fish. Cytogenetic data for Lutjanidae are scarce. In the present work, we cytogenetically characterized through conventional Giemsa staining techniques, Ag-NOR and C-banding the species Ocyurus chrysurus, Lutjanus analis, L. alexandrei, L. cyanopterus, L. jocu and L. synagris, all found along the Brazilian coast. Karyotype analysis of all six species showed a modal value of 2n = 48 acrocentric chromosomes. Single NORs were found at pericentromeric position on the long arms of the 2nd pair in O. chrysurus, L. alexandrei and L. cyanopterus, on the 5th pair in L. analis and on the 23rd pair in L. synagris. The species L. jocu presented multiple NORs located on the 2nd pair at a pericentromeric region and on the 5th pair at a telomeric region. Heterochromatic blocks were identified at the centromeric region of all chromosomes of the studied species. These results indicate that, despite of the chromosomal stability of this family, a relative structural diversification seems to have occurred in the chromosome evolution of the group. Such diversification was evidenced by divergent number and location of ribosomal sites among species. The NOR-bearing pairs represented an efficient cytotaxonomic marker for most of the analyzed species. The data suggest that the presence of interstitially located single NORs on a large acrocentric pair should represent a basal condition for lutjanids.

Cytogenetic analyses performed in populations of the Neotropical freshwater fish Leporinus elongatus of the Upper Paraná River basin showed a chromosome polymorphism involving heterochromatic segments of the nucleolar organizing pair in this species. The NOR-bearing chromosome pair was characterized by two phenotypes identified by the absence (C¹) or presence (C²) of a heterochromatic segment located in an interstitial position of the long arm in this pair. The meiotic segregation of these variations results in three distinct cytotypes, C¹C¹, C¹C² and C²C². Both populations were in Hardy-Weinberg equilibrium. Sex-related cytotype divergence was identified and multivariate analyses revealed that the C²C² individuals presented morphometric differentiation relative to body height in relation to the other cytotypes. A chromosome differentiation and a cytotype proportion difference observed between both populations suggest the occurrence of population subdivision within this species along the Upper Paraná River basin. These findings might contribute to the knowledge of the population biology of this fish and for its conservation.

Although several cases of natural triploidy in fish have already been described, spontaneous polyploidy in species with differentiated sex chromosomes are rare. We report the occurrence of a triploid fish (3n = 81) Leporinus cf. elongatus, a species characterized by a highly differentiated ZZ/ZW sex chromosome system, from the São Francisco river. The occurrence of a ZZZ triploid adult indicates the viability of this chromosome constitution in this fish.

Damselfishes (Pomacentridae, Perciformes) occur in all major oceans of the world and, with approximately 320 species, represent one of the most diverse families of marine Teleostei. The taxonomy of these reef fishes is problematic because of the large number of complex species and the range of color patterns they display, which vary among individuals and populations of the same species. In this study, we examined the cytogenetic composition of four species of Stegastes (S. pictus, S. fuscus, S. variabilis and S. leucostictus) found along the coast of Brazil. Stegastes pictus had a chromosomal number of 2n = 48 (14m+28sm+2st+4a, fundamental number (FN) = 92), S. fuscus had 2n = 48 (20m+22sm+6a, FN = 90), S. variabilis had 2n = 48 (18m+22sm+8a, FN = 88), and S. leucostictus had 2n = 48, (18m+22sm+8a, FN = 88). The nucleolar organizing regions were single and homologous in all of the species, and were located in the interstitial region on the short arm of the first submetacentric pair. The heterochromatin segments were reduced in size and were distributed conservatively over the centromeric and pericentromeric regions of most of the chromosomes. The marked divergence in the number of chromosomal arms, compared to other perciformes (2n = 48, FN = 48), indicated that varying degrees of multiple pericentric inversions had occurred during the karyotypic evolution of the Pomacentridae. Subtle karyotypic differences between S. variabilis and S. leucostictus suggested a recent divergence or that their karyotypes were less susceptible to changes. These results indicate that cytogenetic analyses could provide important complementary data for the characterization of populations and species of Stegastes and damselfishes in general.

Cromossomos mitóticos de duas especies de peixes neotropicais, Leporinus elongatus (Characiformes) e Liposarcus anisitsi (Siluriformes), foram estudados por diferentes métodos de bandamentos, com o intuito de investigar a diferenciação da heterocromatina. Enquanto que a macroestrutura cariotípica de L. elongatus já foi objeto de estudos anteriores, o cariótipo de L. anisitsi está sendo apresentado pela primeira vez. Em ambas as espécies, a coloração dos cromossomos com a mitramicina (MM), fluorocromo GC específico, evidenciou sinais brilhantes em alguns segmentos heterocromáticos também positivos ao bandamento C, sugerindo ser esta fração da heterocromatina rica em seqüências de bases GC. O tratamento dos cromossomos com solução salina aquecida e posterior coloração com Giemsa demonstrou resultados similares, documentando a estabilidade térmica do DNA rico em bases GC, presente na heterocromatina constitutiva. Em L. elongatus a Ag-NOR também seguiu os padrões de bandamentos acima. Em L. anisitsi, contudo, a Ag-NOR apresentou-se MM+ mas negativamente corada após o bandamento C e o tratamento com solução salina aquecida. Por outro lado, em L. elongatus, alguns segmentos que foram positivos ao bandamento C mostraram-se negativos à coloração com mitramicina, assim como à coloração com Giemsa após o tratamento térmico com solução salina. Os resultados obtidos evidenciam a heterogeneidade da heterocromatina no complemento cariotípico das espécies estudadas.

The chromosomes of two neotropical freshwater fish species, namely Liposarcus anisitsi (Siluriformes, Loricariidae) and Leporinus elongatus (Characiformes, Anostomidae), were investigated by means of C-banding, Ag-NORs, fluorochrome staining and banding by hot saline solution (HSS) treatment, to reveal patterns of heterochromatin differentiation. The karyotype of L. anisitsi is described for the first time. Staining with the GC-specific fluorescent antibiotic mithramycin (MM) revealed bright signals in some C-banded blocks in both species, suggesting that these MM+ heterochromatin contains GC-rich DNA. Banding by denaturation employing HSS, followed by Giemsa staining, yielded corresponding results documenting the thermal stability of GC-rich DNA part of heterochromatin positive after C-banding. In L. elongatus the Ag-NOR also followed the above banding patterns. However, in L. anisitsi the Ag-NOR was MM+ but negatively stained after C-banding and HSS treatment. L. elongatus also showed C-banded segments that were negative for mithramycin staining and HSS treatment. The results obtained evidence the heterochromatin heterogeneity in these fish species.