The synthetic dye malachite green found in food induces cytotoxicity and genotoxicity in four different mammalian cell lines from distinct tissuesw

Malachite green (MG) is a synthetic dye that uses ranges from its application as a tissue dye to that as an antiparasitic in aquaculture. Several studies have reported the presence of this compound in food dyes and in the meat of fish raised in captivity for human consumption, suggesting risks both for the end user and for as those who handle these products because of MG toxic properties described in the literature. Here we evaluated the cytotoxic and genotoxic profiles of MG in four different cell lines (ACP02, L929, MNP01, and MRC-5). Two of these cell lines are stomach cells (normal and cancer lineages) and the potential ingestion of MG makes this a relevant cell type. Cells were treated with MG at concentrations ranging from 0.1 μM to 100 μM, and tested by MTT assay, a differential apoptosis/necrosis assay (EB/OA), the micronucleus test (MN), and the comet assay. MG exhibits dose-dependent cytotoxicity toward all of the tested cell types; higher concentrations of MG cause cell necrosis, while lower concentrations induce apoptosis. MG has a genotoxic profile increasing the rates of micronuclei, nucleoplasmic bridges, nuclear buds, and DNA fragmentation; L929 and MRC-5 showed more sensibility than ACP02 and MNP01.

Karyotypes of Manatees: New Insights into Hybrid Formation (Trichechus inunguis × Trichechus m. manatus) in the Amazon Estuary

Great efforts have been made to preserve manatees. Recently, a hybrid zone was described between Trichechus inunguis (TIN) and the Trichechus manatus manatus (TMM) in the Amazon estuary. Cytogenetic data on these sirenians are limited, despite being fundamental to understanding the hybridization/introgression dynamics and genomic organization in Trichechus. We analyzed the karyotype of TMM, TIN, and two hybrid specimens ("Poque" and "Vitor") by classical and molecular cytogenetics. G-band analysis revealed that TMM (2n = 48) and TIN (2n = 56) diverge by at least six Robertsonian translocations and a pericentric inversion. Hybrids had 2n = 50, however, with Autosomal Fundamental Number (FNA) = 88 in "Poque" and FNA = 74 in "Vitor", and chromosomal distinct pairs in heterozygous; additionally, "Vitor" exhibited heteromorphisms and chromosomes whose pairs could not be determined. The U2 snDNA and Histone H3 multi genes are distributed in small clusters along TIN and TMM chromosomes and have transposable Keno and Helitron elements (TEs) in their sequences. The different karyotypes observed among manatee hybrids may indicate that they represent different generations formed by crossing between fertile hybrids and TIN. On the other hand, it is also possible that all hybrids recorded represent F1 and the observed karyotype differences must result from mechanisms of elimination.

Isolation and establishment of skin-derived and mesenchymal cells from south American bat Artibeus planirostris (Chiroptera - Phyllostomidae)

Animal models represent a crucial tool for biological research, so the establishment of new cultures is fundamental for the discovery of new therapies and the understanding of mechanisms of cell development in the most diverse animals. Here, we report the successful establishment of two new primary cell cultures derived from a South American bat (Artibeus planirostris). The establishment of a new bat culture can help in the investigation of new zoonoses since bats have been proposed as carriers of these diseases. We evaluated the chromosomal stability of cells from different passages. Primary cultures were collected from ear tissues and bone marrow of A. planirostris. Cultures were expanded, and osteogenic and adipogenic inductions were conducted for 21 days. For osteogenic differentiation, the medium was supplemented with 0.1 μM dexamethasone, 3 mM β-glycerophosphate, and 10 μM L-ascorbic acid 2-phosphate. For adipogenic differentiation, the medium was supplemented with 5 μM rosiglitazone, 0.4 μM insulin, 0.1 mM indomethacin, and 0.1 μM dexamethasone. After the induction period, the cells were stained with Alizarin Red to assess osteogenic differentiation and Oil Red O to assess adipogenic differentiation. We observed the appearance of lipid droplets in adipocytes and the extracellular deposition of calcium matrix by osteocytes, indicating that bone marrow-derived cells and skin-derived cells of A. planirostris could successfully differentiate into these lineages. Also, the number of chromosomes remained stable for both primary cultures during passages 2, 4, 6, and 8.

Betaine-loaded CaCO3 microparticles improve survival of vitrified feline preantral follicles through higher mitochondrial activity and decreased reactive oxygen species

Ovary fragments from six sexually mature cats were vitrified in the presence or absence of betaine or ascorbic acid, loaded (7.4 or 74µM betaine; 20 or 200µM ascorbic acid) or not (1mM betaine or 0.3mM ascorbic acid) into CaCO3 microparticles, and assessed for follicular morphology, oxidative stress and mitochondrial activity Feline ovarian tissue was successfully preserved after vitrification in the presence of 74µM betaine loaded in CaCO3 microparticles, as confirmed by morphological analysis and the density of preantral follicles and stromal cells, as well as by the increased mitochondrial activity and decreased production of reactive oxygen species.

Chromosome evolution in Lophyohylini (Amphibia, Anura, Hylinae)

The hyline tribe Lophyohylini includes 87 species of treefrogs, of which cytogenetics aspects have been studied in less than 20% of them. In order to evaluate the evolution of some of its chromosome characters (NOR position, C-bands, and DAPI/CMA₃ bands), we studied the karyotypes of 21 lophyohylines, 16 of them for the first time, and analyzed them in a phylogenetic context. Most species showed similar karyotypes regarding chromosome number (2n = 24) and morphology (FN = 48), excepting Phyllodytes edelmoi and Osteocephalus buckleyi with 2n = 22 (FN = 44) and 2n = 28 (FN = 50), respectively. The NOR location was variable among species and provided valuable phylogenetic information. This marker was located in pair 11 in all species of Trachycephalus, Itapotihyla langsdorffii, and Nyctimantis arapapa, representing the plesiomorphic condition of Lophyohylini. Besides, other apomorphic states were recovered for the clades comprising N. rugiceps and N. siemersi (NOR in pair 5), and Dryaderces pearsoni, Osteocephalus, and Osteopilus (NOR in pair 9). Phyllodytes presented variation for NORs position; they were in pair 2 in P. edelmoi, pair 7 in P. melanomystax, and pair 8 in P. gyrinaethes and P. praeceptor. Polymorphisms in size, number, and activity of this marker were observed for N. siemersi, Osteocephalus fuscifacies, and some species of Trachycephalus. Remarkably, in N. siemersi NORs were detected on a single chromosome in the two specimens studied by this technique, raising the question of how this complex polymorphism is maintained. Interstitial telomeric sequences were found in P. edelmoi, P. melanomystax, and Osteocephalus buckleyi, and their presence seems to be not related to the chromosome reorganization events. Finally, some species showed spontaneous rearrangements, possibly as a consequence of an uncommon phenomenon in anuran cytogenetics: the presence of fragile sites or secondary constrictions not associated with NORs. We propose that this rare feature would have played an important role in the evolution of this group of frogs. From the evidence obtained in this and previous studies, we conclude that Lophyohylini presents a complex chromosome evolution.

Karyotypic Diversity and Evolution in a Sympatric Assemblage of Neotropical Electric Knifefish

Chromosome changes can perform an important role in speciation by acting as post-zygotic reproductive barriers. The Neotropical electric fish genus Brachyhypopomus (Gymnotiformes, Hypopomidae) has 28 described species, but cytogenetic data are hitherto available only for four of them. To understand karyotype evolution and investigate the possible role of chromosome changes in the diversification of this genus, we describe here the karyotype of eight species of Brachyhypopomus from a sympatric assemblage in the central Amazon basin. We analyzed cytogenetic data in the context of a phylogenetic reconstruction of the genus and known patterns of geographical distribution. We found a strong phylogenetic signal for chromosome number and noted that sympatric species have exclusive karyotypes. Additional insights into the role of chromosome changes in the diversification of Brachyhypopomus are discussed.

Chromosome evolution in Cophomantini (Amphibia, Anura, Hylinae)

The hylid tribe Cophomantini is a diverse clade of Neotropical treefrogs composed of the genera Aplastodiscus, Boana, Bokermannohyla, Hyloscirtus, and Myersiohyla. The phylogenetic relationships of Cophomantini have been comprehensively reviewed in the literature, providing a suitable framework for the study of chromosome evolution. Employing different banding techniques, we studied the chromosomes of 25 species of Boana and 3 of Hyloscirtus; thus providing, for the first time, data for Hyloscirtus and for 15 species of Boana. Most species showed karyotypes with 2n = 2x = 24 chromosomes; some species of the B. albopunctata group have 2n = 2x = 22, and H. alytolylax has 2n = 2x = 20. Karyotypes are all bi-armed in most species presented, with the exception of H. larinopygion (FN = 46) and H. alytolylax (FN = 38), with karyotypes that have a single pair of small telocentric chromosomes. In most species of Boana, NORs are observed in a single pair of chromosomes, mostly in the small chromosomes, although in some species of the B. albopunctata, B. pulchella, and B. semilineata groups, this marker occurs on the larger pairs 8, 1, and 7, respectively. In Hyloscirtus, NOR position differs in the three studied species: H. alytolylax (4p), H. palmeri (4q), and H. larinopygion (1p). Heterochromatin is a variable marker that could provide valuable evidence, but it would be necesserary to understand the molecular composition of the C-bands that are observed in different species in order to test its putative homology. In H. alytolylax, a centromeric DAPI+ band was observed on one homologue of chromosome pair 2. The band was present in males but absent in females, providing evidence for an XX/XY sex determining system in this species. We review and discuss the importance of the different chromosome markers (NOR position, C-bands, and DAPI/CMA3 patterns) for their impact on the taxonomy and karyotype evolution in Cophomantini.

Extensive Karyotype Reorganization in the Fish Gymnotus arapaima (Gymnotiformes, Gymnotidae) Highlighted by Zoo-FISH Analysis

The genus Gymnotus (Gymnotiformes) contains over 40 species of freshwater electric fishes exhibiting a wide distribution throughout Central and South America, and being particularly prevalent in the Amazon basin. Cytogenetics has been an important tool in the cytotaxonomy and elucidation of evolutionary processes in this genus, including the unraveling the variety of diploid chromosome number (2n = from 34 to 54), the high karyotype diversity among species with a shared diploid number, different sex chromosome systems, and variation in the distribution of several Repetitive DNAs and colocation and association between those sequences. Recently whole chromosome painting (WCP) has been used for tracking the chromosomal evolution of the genus, showing highly reorganized karyotypes and the conserved synteny of the NOR bearing par within the clade G. carapo. In this study, painting probes derived from the chromosomes of G. carapo (GCA, 2n = 42, 30 m/sm + 12 st/a) were hybridized to the mitotic metaphases of G. arapaima (GAR, 2n = 44, 24 m/sm + 20 st/a). Our results uncovered chromosomal rearrangements and a high number of repetitive DNA regions. From the 12 chromosome pairs of G. carapo that can be individually differentiated (GCA1-3, 6, 7, 9, 14, 16, and 18-21), six pairs (GCA 1, 9, 14, 18, 20, 21) show conserved homology with GAR, five pairs (GCA 1, 9, 14, 20, 21) are also shared with cryptic species G. carapo 2n = 40 (34 m/sm + 6 st/a) and only the NOR bearing pair (GCA 20) is shared with G. capanema (GCP 2n = 34, 20 m/sm + 14 st/a). The remaining chromosomes are reorganized in the karyotype of GAR. Despite the close phylogenetic relationships of these species, our chromosome painting studies demonstrate an extensive reorganization of their karyotypes.

New insights of karyoevolution in the Amazonian turtles Podocnemis expansa and Podocnemis unifilis (Testudines, Podocnemidae)

BACKGROUND

Cytogenetic studies were conducted in the Brazilian Amazon turtles, Podocnemis expansa Schweigger, 1912 (PEX) and Podocnemis unifilis Troschel, 1848 (PUN) to understand their karyoevolution. Their chromosomal complements were compared using banding techniques (C, G-, Ag-NOR and Chromomycin A₃) and fluorescence in situ hybridization (FISH), and efforts were made to establish evolutionary chromosomal relationships within the Podocnemidae family.

RESULTS

Our results revealed that both species have a chromosome complement of 2n = 28. For PEX and PUN, the fundamental numbers (FNs) were 54 and 52, respectively and the karyotypic formulas (KFs) were 24 m/sm + 2st + 2a and 22 m/sm + 2st + 4a, respectively. G-banding evidenced homologies between the two species and allowed identify a heteromorphic pair (chromosome pair 10) in PUN. In PEX, constitutive heterochromatin (CH) was found in the centromeric regions of pairs 1, 2, 4, 6 and 11 and on 9p. In PUN, CH was observed in the centromeric regions of all chromosomes, and in small proximal bands on 1p, 2p, 3q, 4q, 5q, 9q, 10q and 11q. Moreover, CH amplification was seen in one of the homologs of pair 10 (the heteromorphic pair). The CMA3 staining results were consistent with the CH findings. Ag-NOR staining showed that nucleolar organizing regions (NORs) were localized in the pericentromeric region of pair 1 in both species, and this result was confirmed by the 18S rDNA FISH probe. FISH with telomeric probes identified telomeric sequences in the distal regions of all chromosomes. In addition, interstitial telomeric sequences (ITSs) were present in seven chromosome pairs of PUN, perhaps reflecting the amplification of telomere-like sequences. FISH with a probe against the transposable element (TE), Rex 6, revealed that it is dispersed in euchromatic regions of the first chromosome pairs of both species. This is the first report describing the FISH-based analysis of PEX and PUN for the 18S rDNA, Rex 6 and human telomeric sequences.

CONCLUSIONS

Our results contribute to clarifying the chromosomal homologies and rearrangement mechanisms that occurred during the evolution of these species, and may help researchers uncover new markers that will improve our understanding of the taxonomy and systematic classification of Podocnemidae.

TRIAL REGISTRATION

ISRCTN ISRCTN73824458. Registered 28 September 2014. Retrospectively registered.

Cryptic Species in Proechimys goeldii (Rodentia, Echimyidae)? A Case of Molecular and Chromosomal Differentiation in Allopatric Populations

The spiny rats of the genus Proechimys have a wide distribution in the Amazon, covering all areas of endemism of this region. We analyzed the karyotype and cytochrome b (Cyt b) sequences in Proechimys goeldii from 6 localities representing 3 interfluves of the eastern Amazon. A clear separation of P. goeldii into 2 monophyletic clades was observed, both chromosomally and based on Cyt b sequences: cytotype A (2n = 26x2640;/27x2642;, NF = 42) for samples from the Tapajos-Xingu interfluve and cytotype B (2n = 24x2640;/25x2642;, NF = 42) for samples from the Xingu-Tocantins interfluve and east of the Tocantins River. The karyotypes differ in a pericentric inversion and a centric fusion/fission and an average nucleotide divergence of 6.1%, suggesting cryptic species. Meiotic analysis confirmed the presence of a XX/XY1Y2 multiple sex chromosome determination system for both karyotypes. The karyotypes also vary from the literature (2n = 24, NF = 42, XX/XY). The autosome translocated to the X chromosome is different both in size and morphology to P. cf. longicaudatus, which also has a multiple sex chromosome determination system (2n = 14x2640;/15x2640;x2642;/16x2640;/17x2642;, NF = 14). The Xingu River is a barrier that separates populations of P. goeldii, thus maintaining their allopatric nature and providing an explanation for the molecular and cytogenetic patterns observed for the Xingu River but not the Tocantins River.

Diversity and Karyotypic Evolution in the Genus Neacomys (Rodentia, Sigmodontinae)

Neacomys (Sigmodontinae) comprises 8 species mainly found in the Amazonian region. We describe 5 new karyotypes from Brazilian Amazonia: 2 cytotypes for N. paracou (2n = 56/FNa = 62-66), 1 for N. dubosti (2n = 64/FNa = 68), and 2 for Neacomys sp. (2n = 58/FNa = 64-70), with differences in the 18S rDNA. Telomeric probes did not show ITS. We provide a phylogeny using Cytb, and the analysis suggests that 2n = 56 with a high FNa is ancestral for the genus, as found in N. paracou, being retained by the ancestral forms of the other species, with an increase in 2n occurring independently in N. spinosus and N. dubosti. Alternatively, an increase in 2n may have occurred in the ancestral taxon of the other species, followed by independent 2n-reduction events in Neacomys sp. and in the ancestral species of N. tenuipes, N. guianae, N. musseri, and N. minutus. Finally, a drastic reduction event in the diploid number occurred in the ancestral species of N. musseri and N. minutus which exhibit the lowest 2n of the genus. The karyotypic variations found in both intra- and interspecific samples, associated with the molecular phylogeny, suggest a chromosomal evolution with amplification/deletion of constitutive heterochromatin and rearrangements including fusions, fissions, and pericentric inversions.

Karyotypic and morphological divergence between two cryptic species of Eigenmannia in the Amazon basin with a new occurrence of XX/XY sex chromosomes (Gymnotiformes: Sternopygidae)

Eigenmannia species are widely distributed in the Neotropics, with eight valid species currently recognized. Populations of Eigenmannia from three locations in the eastern Amazon were investigated using cytogenetic and morphological techniques, revealing two taxa designated here as Eigenmannia sp. "A" and Eigenmannia sp. "B". The species differ in three morphometric characters, two meristic characters, and one osteological character. Eigenmannia sp. "A" presents 2n = 34 (22 m/sm+12 st/a) and Eigenmannia sp. "B" presents 2n = 38 (14 m/sm+24st/a) and simple differentiated sex chromosomes of the type XX/XY. In both species the Constitutive Heterochromatin (CH) rich in A-T bases is distributed in the centromeric region of all chromosomes. Eigenmannia sp. "B" also presents CH blocks in the interstitial region of chromosome pairs 8, 9 and X which are positively stained with CMA3, indicating G-C rich regions. The NOR is located on the short arm of chromosome pair 17 of Eigenmannia sp. "A" and on the short arm of pair 14 of Eigenmannia sp. "B". FISH with rDNA probes hybridized to different-sized regions between homologs, suggesting heteromorphism. The differentiation of the X chromosome in Eigenmannia sp. "B" could be the result of amplification of repetitive DNA sequences.

FISH in micronucleus test demonstrates aneugenic action of rotenone in a common freshwater fish species, Nile tilapia (Oreochromis niloticus)

Aneuploidies are numerical genetic alterations that lead to changes in the normal number of chromosomes due to abnormal segregation during cell division. This type of alteration can occur spontaneously or as a result of exposure to mutagenic agents. The presence of these agents in the environment has increased concern about potential damage to human health. Rotenone, derived from plants of the genera Derris and Lonchocarpus, is a product that is used all over the world as a pesticide and piscicide. Before establishing its potential and efficiency for these purposes, it is essential to know more about the possible adverse effects that it may cause. The current work aimed to evaluate the mutagenic potential of rotenone using fish from the species Oreochromis niloticus, as well as to help in understanding its action mechanism. Our results showed the mutagenic potential of rotenone evidenced by increased formation of micronuclei and nuclear buds at low doses of exposure. The use of fluorescence in situ hybridisation technique made it possible to measure the aneugenic potential of the substance, probably due to its impairment of mitotic spindle formation.

Two new cytotypes reinforce that Micronycteris hirsuta Peters, 1869 does not represent a monotypic taxon

Background

The genus Micronycteris is a diverse group of phyllostomid bats currently comprising 11 species, with diploid number (2n) ranging from 26 to 40 chromosomes. The karyotypic relationships within Micronycteris and between Micronycteris and other phyllostomids remain poorly understood. The karyotype of Micronycteris hirsuta is of particular interest: three different diploid numbers were reported for this species in South and Central Americas with 2n = 26, 28 and 30 chromosomes. Although current evidence suggests some geographic differentiation among populations of M. hirsuta based on chromosomal, morphological, and nuclear and mitochondrial DNA markers, the recognition of new species or subspecies has been avoided due to the need for additional data, mainly chromosomal data.

Results

We describe two new cytotypes for Micronycteris hirsuta (MHI) (2n = 26 and 25, NF = 32), whose differences in diploid number are interpreted as the products of Robertsonian rearrangements. C-banding revealed a small amount of constitutive heterochromatin at the centromere and the NOR was located in the interstitial portion of the short arm of a second pair, confirmed by FISH. Telomeric probes hybridized to the centromeric regions and weakly to telomeric regions of most chromosomes. The G-banding analysis and chromosome painting with whole chromosome probes from Carollia brevicauda (CBR) and Phyllostomus hastatus (PHA) enabled the establishment of genome-wide homologies between MHI, CBR and PHA.

Conclusions

The karyotypes of Brazilian specimens of Micronycteris hirsuta described here are new to Micronycteris and reinforce that M. hirsuta does not represent a monotypic taxon. Our results corroborate the hypothesis of karyotypic megaevolution within Micronycteris, and strong evidence for this is that the entire chromosome complement of M. hirsuta was shown to be derivative with respect to species compared in this study.

Genetic and morphological variability in South American rodent Oecomys (Sigmodontinae, Rodentia): evidence for a complex of species

The rodent genus Oecomys (Sigmodontinae) comprises ~16 species that inhabit tropical and subtropical forests in Central America and South America. In this study specimens of Oecomys paricola Thomas, 1904 from Belém and Marajó island, northern Brazil, were investigated using cytogenetic, molecular and morphological analyses. Three karyotypes were found, two from Belém (2n = 68, fundamental number (FN) = 72 and 2n = 70, FN = 76) and a third from Marajó island (2n = 70, FN = 72). No molecular or morphological differences were found between the individuals with differing cytotypes from Belém, but differences were evident between the individuals from Belém and Marajó island. Specimens from Belém city region may represent two cryptic species because two different karyotypes are present in the absence of significant differences in morphology and molecular characteristics. The Marajó island and Belém populations may represent distinct species that have been separated for some time, and are in the process of morphological and molecular differentiation as a consequence of reproductive isolation at the geographic and chromosomal levels. Thus, the results suggest that O. paricola may be a complex of species.

Chromosome evolution in dendropsophini (Amphibia, Anura, Hylinae)

Dendropsophini is the most species-rich tribe within Hylidae with 234 described species. Although cytogenetic information is sparse, chromosome numbers and morphology have been considered as an important character system for systematic inferences in this group. Using a diversity of standard and molecular techniques, we describe the previously unknown karyotypes of the genera Xenohyla, Scarthyla and Sphaenorhynchus and provide new information on Dendropsophus and Lysapsus. Our results reveal significant karyotype diversity among Dendropsophini, with diploid chromosome numbers ranging from 2n = 22 in S. goinorum, 2n = 24 in Lysapsus, Scinax, Xenohyla, and almost all species of Sphaenorhynchus and Pseudis, 2n = 26 in S. carneus, 2n = 28 in P. cardosoi, to 2n = 30 in all known Dendropsophus species. Although nucleolar organizer regions (NORs) and C-banding patterns show a high degree of variability, NOR positions in 2n = 22, 24 and 28 karyotypes and C-banding patterns in Lysapsus and Pseudis are informative cytological markers. Interstitial telomeric sequences reveal a diploid number reduction from 24 to 22 in Scarthyla by a chromosome fusion event. The diploid number of X. truncata corroborates the character state of 2n = 30 as a synapomorphy of Dendropsophus.

Chromosome painting reveals multiple rearrangements between Gymnotus capanema and Gymnotus carapo (Gymnotidae, Gymnotiformes)

The genus Gymnotus (Gymnotiformes) is a group of fishes with karyotypic plasticity, demonstrated by cytogenetic studies using whole chromosome probes of G. carapo (GCA, 2n = 42) that were obtained by flow-sorting from fibroblast cultures. In the present work we undertook comparative mapping of the karyotype of G. capanema (GCP, 2n = 34) with GCA, 2n = 42 painting probes. The results demonstrate that the karyotype of G. capanema is extensively rearranged when compared to G. carapo. From the 12 chromosome pairs of G. carapo that can be individually differentiated (GCA1-3, 6, 7, 9, 14, 16 and 18-21), only 4 pairs (GCA6, 7, 19, and 20) maintained conserved synteny in G. capanema. From these 4, GCA6 and GCA20 correspond to individual chromosomes (GCP8 and GCP15), while the other 2 share homology with parts of GCP1 and GCP2, respectively. The remaining GCP chromosomes showed more complex hybridization patterns with homologies to other GCA pairs. These results demonstrate that the level of reorganization in the genome of G. capanema is much greater than in GCA, 2n = 42 and in karyomorph GCA, 2n = 40 which was previously analyzed by chromosome painting.

A phylogenetic analysis using multidirectional chromosome painting of three species (Uroderma magnirostrum, U. bilobatum and Artibeus obscurus) of subfamily Stenodermatinae (Chiroptera-Phyllostomidae)

The species of genera Uroderma and Artibeus are medium-sized bats belonging to the family Phyllostomidae and subfamily Stenodermatinae (Mammalia, Chiroptera) from South America. They have a wide distribution in the Neotropical region, with two currently recognized species in Uroderma and approximately 20 species in Artibeus. These two genera have different rates of chromosome evolution, with Artibeus probably having retained the ancestral karyotype for the subfamily. We used whole chromosome paint probe sets from Carollia brevicauda and Phyllostomus hastatus on Uroderma magnirostrum, Uroderma bilobatum, and Artibeus obscurus. With the aim of testing the previous phylogenies of these bats using cytogenetics, we compared these results with published painting maps on Phyllostomidae. The genome-wide comparative maps based on chromosome painting and chromosome banding reveal the chromosome forms that characterize each taxonomic level within the Phyllostomidae and show the chromosome evolution of this family. Based on this, we are able to suggest an ancestral karyotype for Phyllostomidae. Our cladistic analysis is an independent confirmation using multidirectional chromosome painting of the previous Phyllostomidae phylogenies.

Proechimys (Rodentia, Echimyidae): characterization and taxonomic considerations of a form with a very low diploid number and a multiple sex chromosome system

Background

Proechimys is the most diverse genus in family Echimyidae, comprising 25 species (two of which are polytypic) and 39 taxa. Despite the numerous forms of this rodent and their abundance in nature, there are many taxonomic problems due to phenotypic similarities within the genus and high intraspecific variation. Extensive karyotypic variation has been noted, however, with diploid numbers (2n) ranging from 14 to 62 chromosomes. Some heteromorphism can be found, and 57 different karyotypes have been described to date.

Results

In the present work, we describe a cytotype with a very low 2n. Specimens of Proechimys cf. longicaudatus were collected from two different places in northern Mato Grosso state, Brazil (12°54″S, 52°22″W and 9°51′17″S, 58°14′53″W). The females and males had 16 and 17 chromosomes, respectively; all chromosomes were acrocentric, with the exception of the X chromosome, which was bi-armed. The sex chromosome system was found to be XY₁Y₂, originating from a Robertsonian rearrangement involving the X and a large acrocentric autosome. Females had two Neo-X chromosomes, and males had one Neo-X and two Y chromosomes. NOR staining was found in the interstitial region of one autosomal pair.

Conclusions

Comparison of this karyotype with those described in the literature revealed that Proechimys with similar karyotypes had previously been collected from nearby localities. We therefore suggest that this Proechimys belongs to a different taxon, and is either a new species or one that requires reassessment.

Are NORs always located on homeologous chromosomes? A FISH investigation with rDNA and whole chromosome probes in Gymnotus fishes (Gymnotiformes)

Gymnotus (Gymnotiformes, Gymnotidae) is the most diverse known Neotropical electric knife fish genus. Cytogenetic studies in Gymnotus demonstrate a huge karyotypic diversity for this genus, with diploid numbers ranging from 34 to 54. The NOR are also variable in this genus, with both single and multiple NORs described. A common interpretation is that the single NOR pair is a primitive trait while multiple NORs are derivative. However this hypothesis has never been fully tested. In this report we checked if the NOR-bearing chromosome and the rDNA site are homeologous in different species of the genus Gymnotus: G. carapo (2n = 40, 42, 54), G. mamiraua (2n = 54), G. arapaima (2n = 44), G. sylvius (2n = 40), G. inaequilabiatus (2n = 54) and G. capanema (2n = 34), from the monophyletic group G. carapo (Gymnotidae-Gymnotiformes), as well as G. jonasi (2n = 52), belonging to the G1 group. They were analyzed with Fluorescence in situ hybridization (FISH) using 18S rDNA and whole chromosome probes of the NOR-bearing chromosome 20 (GCA20) of G. carapo (cytotype 2n = 42), obtained by Fluorescence Activated Cell Sorting. All species of the monophyletic G. carapo group show the NOR in the same single pair, confirmed by hybridization with CGA20 whole chromosome probe. In G. jonasi the NORs are multiple, and located on pairs 9, 10 and 11. In G. jonasi the GCA20 chromosome probe paints the distal half of the long arm of pair 7, which is not a NOR-bearing chromosome. Thus these rDNA sequences are not always in the homeologous chromosomes in different species thus giving no support to the hypothesis that single NOR pairs are primitive traits while multiple NORs are derived. The separation of groups of species in the genus Gymnotus proposed by phylogenies with morphologic and molecular data is supported by our cytogenetic data.

Gymnotus capanema, a new species of electric knife fish (Gymnotiformes, Gymnotidae) from eastern Amazonia, with comments on an unusual karyotype

Gymnotus capanema n. sp. is described on the basis of cytogenetic, morphometric, meristic and osteological data from nine specimens (one male and eight females) from the municipality of Capanema, Pará, in the eastern Amazon of Brazil. Later, three additional specimens were found in museums and regarded as nontypes (not cytogenetically analysed). Gymnotus capanema, which occurs in sympatry with Gymnotus cf. carapo cytotype 2n = 42 (30m/sm + 12st/a) exhibits a novel karyotype for the genus, with 2n = 34 (20m/sm + 14st/a). Gymnotus capanema can be unambiguously diagnosed from all congeners on the basis of a combination of characters from external anatomy, pigmentation and osteology. The constitutive heterochromatin, rich in adenine-thymine (A-T) base pairs [4',6 diamidino-2-phenylindole dihydrochloride (DAPI) positive], occurs in the centromeric region of all of the chromosomes, and in the pericentromeric and the entire short arm of some chromosomes. The nucleolar organizing region (NOR), stained by silver nitrate, chromomycin A(3) (CMA(3)) and 18S ribosomal (r)DNA fluorescence in situ hybridization (FISH), occurs in the short arm of pair 15. FISH, with telomeric probes did not show interstitial telomeric sequences (ITS), despite the reduced 2n in comparison to the karyotypes of other species of Gymnotus. The karyotype of G. capanema, with a reduced 2n, is strikingly different from all other previously studied congeners.

Analysis of the heterochromatin of Cebus (Primates, Platyrrhini) by micro-FISH and banding pattern comparisons

The karyotype of the neotropical primate genus Cebus (Platyrrhini: Cebidae), considered the most ancestral one, shows the greatest amount of heterochromatin described among Platyrrhini genera. Banding techniques and restriction enzyme digestion have previously revealed great variability of quantity and composition of heterochromatin in this genus. In this context, we use fluorescence in situ hybridization (FISH) to analyse this genomic region and discuss its possible role in the diversification of Cebus.We used a heterochromatin probe for chromosome 11 of Cebus libidinosus (11qHe+ CLI probe), obtained by chromosome microdissection. Twenty-six specimens belonging to the families Atelidae, Cebidae, Callitrichidae and Pithecidae (Platyrrhini) were studied. Fourteen out of 26 specimens were Cebus (Cebidae) individuals of C. libidinosus, C. xanthosternos, C. apella, C. nigritus, C. albifrons, C. kaapori and C. olivaceus. In Cebus specimens, we found 6 to 22 positive signals located in interstitial and telomeric positions along the different species. No hybridization signal was observed among the remaining Ceboidea species, thus reinforcing the idea of a Cebus-specific heterochromatin composed of a complex system of repetitive sequences.

Genomic mapping of human chromosome paints on the threatened masked Titi monkey (Callicebus personatus)

Callicebus is a complex genus of neotropical primates thought to include 29 or more species. Currently, the genus is divided into 5 species groups: donacophilus, cupreus, moloch, torquatus and personatus. However, the phylogenetic relationships among the species are still poorly understood. This genus is karyotypically diverse and shows extensive variation in diploid number (2n = 16 to 50). To foster a better understanding of the chromosomal diversities and phylogenetic relationships among the species of Callicebus, we performed a chromosome-painting analysis on the Callicebus personatus genome using human probes, and compared the resulting hybridization map to those of previously mapped titi species. We detected 38 hybridization signals per haploid autosomal set of C. personatus. Few ancestral syntenies were conserved without rearrangement, but 4 human associations (HSA20/13, 3c/8b, 1b/1c and 21/3a/15a/14) were demonstrated to be apomorphic traits for C. persona tus. G-banding suggested that these associations are shared with C. nigrifrons and C. coimbrai (personatus group), while C. personatus is linked with C. pallescens (donacophilus group) by 2 synapomorphies: HSA10b/11 (submetacentric) and an inversion of HSA1a.

Chromosomal homologies among vampire bats revealed by chromosome painting (phyllostomidae, chiroptera)

Substantial effort has been made to elucidate karyotypic evolution of phyllostomid bats, mostly through comparisons of G-banding patterns. However, due to the limited number of G-bands in respective karyotypes and to the similarity of non-homologous bands, an accurate evolutionary history of chromosome segments remains questionable. This is the case for vampire bats (Desmodontinae). Despite several proposed homologies, banding data have not yet provided a detailed understanding of the chromosomal changes within vampire genera. We examined karyotype differentiation of the 3 species within this subfamily using whole chromosomal probes from Phyllostomus hastatus (Phyllostominae) and Carollia brevicauda (Carolliinae). Painting probes of P. hastatus respectively detected 22, 21 and 23 conserved segments in Diphylla ecaudata, Diaemus youngi, and Desmodus rotundus karyotypes, whereas 27, 27 and 28 were respectively detectedwith C. brevicauda paints. Based on the evolutionary relationships proposed by morphological and molecular data, we present probable chromosomal synapomorphies for vampire bats and propose chromosomes that were present in the common ancestor of the 5 genera analyzed. Karyotype comparisons allowed us to relate a number of conserved chromosomal segments among the 5 species, providing a broader database for understanding karyotype evolution in the family.

Chromosome phylogeny of the subfamily Pitheciinae (Platyrrhini, Primates) by classic cytogenetics and chromosome painting

BACKGROUND

The New World monkey (Platyrrhini) subfamily Pitheciinae is represented by the genera Pithecia, Chiropotes and Cacajao. In this work we studied the karyotypes of Pithecia irrorata (2n = 48) and Cacajao calvus rubicundus (2n = 45 in males and 2n = 46 in females) by G- and C-banding, NOR staining and chromosome painting using human and Saguinus oedipus whole chromosome probes. The karyotypes of both species were compared with each other and with Chiropotes utahicki (2n = 54) from the literature.

RESULTS

Our results show that members of the Pitheciinae have conserved several chromosome forms found in the inferred ancestral Platyrrhini karyotype (associations of human homologous segments 3a/21, 5/7a, 2b/16b, 8a/18, 14/15a and 10a/16a). Further, the monophyly of this subfamily is supported by three chromosomal synapomorphies (2a/10b, an acrocentric 15/14 and an acrocentric human 19 homolog). In addition, each species presents several autapomorphies. From this data set we established a chromosomal phylogeny of Pitheciinae, resulting in a single most parsimonious tree.

CONCLUSIONS

In our chromosomal phylogeny, the genus Pithecia occurred in a more basal position close to the inferred ancestor of Platyrrhini, while C. c. rubicundus and C. utahicki are closely related and are linked by exclusive synapomorphies.

Multiple rearrangements in cryptic species of electric knifefish, Gymnotus carapo (Gymnotidae, Gymnotiformes) revealed by chromosome painting

Background

Gymnotus (Gymnotidae, Gymnotiformes) is the Neotropical electric fish genus with the largest geographic distribution and the largest number of species, 33 of which have been validated. The diploid number varies from 2n = 39-40 to 2n = 54. Recently we studied the karyotype of morphologically indistinguishable samples from five populations of G. carapo sensu stricto from the Eastern Amazon of Brazil. We found two cytotypes, 2n = 42 (30 M/SM + 12 ST/A) and 2n = 40 (34 M/SM + 6 ST/A) and we concluded that the differences between the two cryptic species are due to pericentric inversions and one tandem fusion.

Results

In this study we use for the first time, whole chromosome probes prepared by FACS of the Gymnotus carapo sensu strictu species, cytotype with 2n = 42. Using two color hybridizations we were able to distinguish pairs 1, 2, 3, 7, 9, 14, 16, 18, 19, 20 and 21. It was not possible to separate by FACS and distinguish each of the following chromosome pairs even with dual color FISH: {4,8}; {10,11}; {5,6,17}; {12,13,15}. The FISH probes were then used in chromosome painting experiments on metaphases of the 2n = 40 cytotype. While some chromosomes show conserved synteny, others are rearranged in different chromosomes. Eight syntenic associations were found.

Conclusions

These results show that the karyotype differences between these cryptic species are greater than assumed by classical cytogenetics. These data reinforce the previous supposition that these two cytotypes are different species, despite the absence of morphological differences. Additionally, the homology of repetitive DNA between the two provides evidence of recent speciation.

Reciprocal chromosome painting between white hawk (Leucopternis albicollis) and chicken reveals extensive fusions and fissions during karyotype evolution of accipitridae (Aves, Falconiformes)

Evolutionary cytogenetics can take confidence from methodological and analytical advances that promise to speed up data acquisition and analysis. Drastic chromosomal reshuffling has been documented in birds of prey by FISH. However, the available probes, derived from chicken, have the limitation of not being capable of determining if breakpoints are similar in different species: possible synapomorphies are based on the number of segments hybridized by each of chicken chromosome probes. Hence, we employed FACS to construct chromosome paint sets of the white hawk (Leucopternis albicollis), a Neotropical species of Accipitridae with 2n = 66. FISH experiments enabled us to assign subchromosomal homologies between chicken and white hawk. In agreement with previous reports, we found the occurrence of fusions involving segments homologous to chicken microchromosomes and macrochromosomes. The use of these probes in other birds of prey can identify important chromosomal synapomorphies and clarify the phylogenetic position of different groups of Accipitridae.

Correlation between argyrophilic nucleolar organizer region staining and brain tumor classification and grading

Distinctions between benign and malignant tumors are less evident in the central nervous system than in other tissues. Since the level of cell proliferation is an important feature in tumor grading, we applied AgNOR in 50 cases of brain tumors with different grades and histological origins in order to check its efficiency in discriminating between benign and malignant cases. We found significant differences between the means of grade I (1.76) and grade IV (2.46) tumors. No significant differences were observed considering the same grading with distinct histological types or age of patients, reinforcing the efficiency of AgNOR.

Cytogenetic studies in Eigenmannia virescens (Sternopygidae, Gymnotiformes) and new inferences on the origin of sex chromosomes in the Eigenmannia genus

Background

Cytogenetic studies were carried out on samples of Eigenmannia virescens (Sternopygidae, Gymnotiformes) obtained from four river systems of the Eastern Amazon region (Para, Brazil).

Results

All four populations had 2n = 38, with ZZ/ZW sex chromosomes (Z, acrocentric; W, submetacentric). Constitutive heterochromatin (CH) was found at the centromeric regions of all chromosomes. The W chromosome had a heterochromatic block in the proximal region of the short arm; this CH was positive for DAPI staining, indicating that it is rich in A-T base pairs. The nucleolar organizer region (NOR) was localized to the short arm of chromosome pair 15; this result was confirmed by fluorescent in situ hybridization (FISH) with human 45S rDNA, and CMA₃ staining indicated that the region is G-C rich. FISH with telomeric probes did not show any evidence of interstitial telomeric sequences (ITS).

Conclusion

Previous studies have shown that the species Eigenmannia sp. 2 and E. virescens have differentiated sex chromosomes, and diverse sex chromosome systems have been described for E. virescens specimens obtained from different Brazilian rivers. A comparative analysis of the present data and prior reports suggests that the sex chromosomes of Eigenmannia may have arisen independently in the different populations.

Comparative chromosome painting between chicken and spectacled owl (Pulsatrix perspicillata): implications for chromosomal evolution in the Strigidae (Aves, Strigiformes)

The spectacled owl (Pulsatrix perspicillata), a species found in the Neotropical region, has 76 chromosomes, with a high number of biarmed chromosomes. In order to define homologies between Gallus gallus and Pulsatrixperspicillata (Strigiformes, Strigidae), we used chromosome painting with chicken DNA probes of chromosomes 1-10 and Z and telomeric sequences. This approach allowed a comparison between Pulsatrixperspicillata and other species of Strigidae already analyzed by chromosome painting (Strix nebulosa and Bubo bubo, both with 2n = 80). The results show that centric fusions and fissions have occurred in different chromosomal pairs and are responsible for the karyotypic variation observed in this group. No interstitial telomeric sequences were found. Although the largest pair of chromosomes in P. perspicillata and Bubo bubo are submetacentric, they are homologous to different chicken chromosomes: GGA1/GGA2 in P. perspicillata and GGA2/GGA4 in B. bubo.

Chromosomal evidence for a putative cryptic species in the Gymnotus carapo species-complex (Gymnotiformes, Gymnotidae)

BACKGROUND

In this study we examined the karyotypes of morphologically indistinguishable populations of the electric knifefish Gymnotus carapo sensu stricto from the Eastern Amazon of Brazil. These were identified unambiguously on the basis of external morphology, meristics, and pigmentation.

RESULTS

Specimens from one of five localities exhibited a karyotype previously not documented for Gymnotus species in the Amazon basin: 2n = 40 (34M/SM+6ST/A). Samples from the other four localities exhibited a different karyotype: 2n = 42 (30M/SM+12ST/A), which we had previously described. Specimens from all five localities presented constitutive heterochromatin in the centromeric region of almost all chromosomes, including in the distal and interstitial regions. Staining with 4'6-Diamidino-2-phenylindole revealed C-positive banding. In both karyotypes the Nucleolar Organizer Region (NOR) was located on the short arm of pair 20, and Chromomycin A3 stained the NORs. Fluorescent in situ hybridization with telomeric probes showed an Interstitial Telomeric Sequence (ITS) in the proximal short arm of a metacentric pair in the 2n = 40 karyotype.

CONCLUSION

The difference between the two karyotypes on the diploid number and chromosome morphology can be explained by rearrangements of the fusion-fission type and also by pericentric inversions. The presence of ITS in a metacentric pair of the 2n = 40 karyotype suggests that the difference in the diploid number of the karyotypes results from a fusion. The consistent 2n = 42 karyotype at four localities suggests an interbreeding population. However, because fusion-fission and pericentric inversions of this nature typically result in reproductive isolation, we speculate that the form with the 2n = 40 karyotype is a different species to that of the 2n = 42 form. Nonetheless, we did not observe evident differences in external morphology, meristics and pigmentation between the two forms, which suggest that they represent cryptic sympatric species in the G. carapo species complex. We speculate that the chromosomal speciation occurred recently, allowing insufficient time for the fixation of other differences following post-zygotic isolation.

Phylogenetic studies of the genus Cebus (Cebidae-Primates) using chromosome painting and G-banding

BACKGROUND

Chromosomal painting, using whole chromosome probes from humans and Saguinus oedipus, was used to establish karyotypic divergence among species of the genus Cebus, including C. olivaceus, C. albifrons, C. apella robustus and C. apella paraguayanus. Cytogenetic studies suggested that the species of this genus have conservative karyotypes, with diploid numbers ranging from 2n = 52 to 2n = 54.

RESULTS

Banding studies revealed morphological divergence among some chromosomes, owing to variations in the size of heterochromatic blocks. This analysis demonstrated that Cebus species have five conserved human associations (i.e., 5/7, 2/16, 10/16, 14/15, 8/18 and 3/21) when compared with the putative ancestral Platyrrhini karyotype.

CONCLUSION

The autapomorphies 8/15/8 in C. albifrons and 12/15 in C. olivaceus explain the changes in chromosome number from 54 to 52. The association 5/16/7, which has not previously been reported in Platyrrhini, was also found in C. olivaceus. These data corroborate previous FISH results, suggesting that the genus Cebus has a very similar karyotype to the putative ancestral Platyrrhini.

Low rate of genomic repatterning in Xenarthra inferred from chromosome painting data

Comparative cytogenetic studies on Xenarthra, one of the most basal mammalian clades in the Placentalia, are virtually absent, being restricted largely to descriptions of conventional karyotypes and diploid numbers. We present a molecular cytogenetic comparison of chromosomes from the two-toed (Choloepus didactylus, 2n = 65) and three-toed sloth species (Bradypus tridactylus, 2n = 52), an anteater (Tamandua tetradactyla, 2n = 54) which, together with some data on the six-banded armadillo (Euphractus sexcinctus, 2n = 58), collectively represent all the major xenarthran lineages. Our results, based on interspecific chromosome painting using flow-sorted two-toed sloth chromosomes as painting probes, show the sloth species to be karyotypically closely related but markedly different from the anteater. We also test the synteny disruptions and segmental associations identified within Pilosa (anteaters and sloths) against the chromosomes of the six-banded armadillo as outgroup taxon. We could thus polarize the 35 non-ambiguously identified chromosomal changes characterizing the evolution of the anteater and sloth genomes and map these to a published sequence-based phylogeny for the group. These data suggest a low rate of genomic repatterning when placed in the context of divergence estimates based on molecular and fossil data. Finally, our results provide a glimpse of a likely ancestral karyotype for the extant Xenarthra, a pivotal group for understanding eutherian genome evolution.

Reciprocal chromosome painting between two South American bats: Carollia brevicauda and Phyllostomus hastatus (Phyllostomidae, Chiroptera)

The Neotropical Phyllostomidae family is the third largest in the order Chiroptera, with 56 genera and 140 species. Most researchers accept this family as monophyletic but its species are anatomically diverse and complex, leading to disagreement on its systematics and evolutionary relationships. Most of the genera of Phyllostomidae have highly conserved karyotypes but with intense intergeneric variability, which makes any comparative analysis using classical banding difficult. The use of chromosome painting is a modern way of genomic comparison on the cytological level, and will clarify the intense intergenus chromosomal variability in Phyllostomidae. Whole chromosome probes of species were produced as a tool for evolutionary studies in this family from two species from different subfamilies, Phyllostomus hastatus and Carollia brevicauda, which have large morphological and chromosomal differences, and these probes were used in reciprocal chromosome painting. The hybridization of the Phyllostomus probes on the Carollia genome revealed 24 conserved segments, while the Carollia probes on the Phyllostomus genome detected 26 segments. Many chromosome rearrangements have occurred during the divergence of these two genera. The sequence of events suggested a large number of rearrangements during the differentiation of the genera followed by high chromosomal stability within each genus.

Phylogenetic inferences of Atelinae (Platyrrhini) based on multi-directional chromosome painting in Brachyteles arachnoides, Ateles paniscus paniscus and Ateles b. marginatus

We performed multi-directional chromosome painting in a comparative cytogenetic study of the three Atelinae species Brachyteles arachnoides, Ateles paniscus paniscus and Ateles belzebuth marginatus, in order to reconstruct phylogenetic relationships within this Platyrrhini subfamily. Comparative chromosome maps between these species were established by multi-color fluorescence in situ hybridization (FISH) employing human, Saguinus oedipus and Lagothrix lagothricha chromosome-specific probes. The three species included in this study and four previously analyzed species from all four Atelinae genera were subjected to a phylogenetic analysis on the basis of a data matrix comprised of 82 discrete chromosome characters. The results confirmed that Atelinae represent a monophyletic clade with a putative ancestral karyotype of 2n = 62 chromosomes. Phylogenetic analysis revealed an evolutionary branching sequence [Alouatta [Brachyteles [Lagothrix and Ateles]]] in Atelinae and [Ateles belzebuth marginatus [Ateles paniscus paniscus [Ateles belzebuth hybridus and Ateles geoffroyi]]] in genus Ateles. The chromosomal data support a re-evaluation of the taxonomic status of Ateles b. hybridus.

A new karyotype of an endangered primate species (Callicebus personatus) from the Brazilian Atlantic forests

The genus Callicebus has 28 species arranged in five groups: donacophilus, torquatus, moloch, cupreus and personatus. The personatus group occurs in the Brazilian Atlantic forests where it is isolated from the other Callicebus groups. The present paper is the first report on the karyotype of Callicebuspersonatus. We compared the karyotypes of C. personatus and C. nigrifrons utilizing the following classic banding techniques: G-, C-, NOR banding, G/C- and G/NOR sequential banding. The karyotype of C. personatus has 2n=44, while C. nigrifrons presented 2n=42. Both the species diverge in the diploid number in consequence of a rearrangement type centric fusion/fission. Our results support personatus as a valid group and the specific status for C. personatus and C. nigrifrons.

Chromosomal studies in Callicebus donacophilus pallescens, with classic and molecular cytogenetic approaches: multicolour FISH using human and Saguinus oedipus painting probes

This paper presents the karyotype of Callicebus donacophilus pallescens for the first time. The analysis included G-, C-, NOR-banding techniques and FISH with chromosome painting probes from Saguinus oedipus and Homo sapiens. The results were compared with the karyotypes of Callicebus moloch donacophilus and C. moloch previously published. These three karyotypes display the same diploid number (2n = 50) but diverge about the number of biarmed and acrocentric chromosomes. The acrocentrics 14 and 15 from C. m. donacophilus and C. moloch have undergone an in-tandem fusion originating a large acrocentric (pair 10) in C. d. pallescens. The major submetacentric pair (pair 1) from C. d. donacophilus and C. moloch have undergone fission originating two acrocentric pairs in C. d. pallescens (pairs 15 and 22). Herein was evidence that, in spite of the high interspecific variation among Callicebus, most of the chromosomes remained conserved.

Cytogenetic study of Callicebus hoffmannsii (Cebidae, Primates) and comparison with C. m. moloch

Callicebus is a neotropical primate genus divided into four or five groups of species. Species of the moloch group are distributed in the tropical forests of the Amazon basin. The karyotype of Callicebus hoffmannsii (moloch group) was studied by means of G- and C-banding, Ag-NOR staining and in situ hybridization of telomeric probes. C. hoffmannsii had 2n = 50 chromosomes, with ten biarmed and fourteen acrocentric autosomal pairs. The X chromosome was submetacentric and the Y chromosome was a minor acrocentric. Constitutive heterochromatin was detected in the centromeric regions of all chromosomes; in pairs 7 and 10, it was found in the distal regions of the short arms, and distally in the long arm of the X chromosome. Size heteromorphism in C-bands was detected in pairs 7 and 10. Ag-NOR staining revealed a maximum of three nucleolar organizers. Telomeric probes hybridized only at the terminal regions of all chromosomes. Additionally, a comparison was carried out between C. hoffmannsii and C. m. moloch (2n = 48), as previously reported. Both species shared gross chromosomal similarities diverging by a single rearrangement of centric fusion/fission. A high similarity between C. hoffmannsii and C. donacophilus indicated a close association between the moloch and donacophilus groups.

Cytogenetic studies on Choeroniscus minor (Chiroptera, Phyllostomidae) from the Amazon region

The Choeroniscus genus (Glossophaginae, Phyllostomidae) has five monotypic species: C. minor, C. godmani, C. intermedius, C. inca and C. periosus. This paper analyses the karyotype of a female C. minor, collected close to the Guama river (Belém, Para, Brazil). G-, C-banding and NOR-staining were performed. This species has 2n = 20 chromosomes, where there are two bi-armed pairs (numbers 1 and 9) and seven subtelocentric pairs (2, 3, 4, 5, 6, 7 and 8). The probable X chromosome is a submetacentric. The constitutive heterochromatin can be found in the short arm of five subtelocentric pairs (4, 5, 6, 7 and 8) and is centromeric in the bi-armed pairs numbers 1 and 9, and the X chromosome. The heterochromatic bands are heteromorphic in three pairs (1, 2 and 3). Active NOR were observed in the short arms of eight subtelocentric chromosomes, suggesting that at least four pairs are nucleolar organizers. This paper describes for the first time the karyotype of C. minor from the Amazon region.

A new karyotype in Callicebus torquatus (Cebidae, Primates)

We describe a new karyotype of Callicebus torquatus using conventional staining, G-banding with Wright Stain, CBG, Ag-NOR staining and fluorescence in situ hybridization (FISH) with human telomere probes and comparative analysis with the previously reported karyotype of C. torquatus torquatus (2n = 20). We studied a female specimen maintained in captivity at the Centro Nacional de Primatas (Para, Brazil). This titi monkey presented 2n = 22, with four large biarmed and six acrocentric autosome pairs; the X chromosome is a medium submetacentric. C-bands were revealed at the centromeric region of all acrocentrics and X chromosome; punctual C-bands also are visualized at the centromeric region in the large biarmed pairs. The NOR site was located at the long arm of pair 4, at the position of a conspicuous secondary constriction. Hybridization signals were detected exclusively at the terminal region of all chromosomes. The karyotype described here has one acrocentric pair more than that found in the literature and also differs by amount and distribution of constitutive heterochromatin. Our data support the notion that the torquatus group may be composed of distinct species, each with its own karyotype.

Restriction enzyme and fluorochrome banding analysis of the constitutive heterochromatin of Saguinus species (Callitrichidae, Primates)

Metaphases of Saguinas fuscicollis fuscicollis and Saguinas mystax were subjected to restriction enzyme banding (Alu I, Hae III, Hin fI, Rsa I, Dde I, Mbo I and Msp I) and sequenced C-banding, together with fluorochrome staining (CMA3 and DAPI). Both species showed large C-bands in the pericentromeric regions. S. f. fuscicollis also manifested distal C-bands in both arms of pair 5 and in the short arms of pairs 8-15. In each species the heterochromatin revealed different reactions to the restriction enzymes and fluorochromes. This was related to its location in the genome (centromeric, pericentromeric, distal), making possible the identification of distinct categories of constitutive heterochromatin. In S. f. fuscicollis there were at least five types, namely centromeric in bi-armed chromosomes, centromeric in acrocentrics, pericentromeric, distal, and cryptic bands, detected only with the Alu I. There were three types in S. mystax, viz centromeric in bi-armed chromosomes, centromeric in acrocentric, and pericentromeric chromosomes. Several aspects of their constitution and origin are discussed.

Chromosome comparison between two species of Phyllostomus (Chiroptera - Phyllostomidae) from Eastern Amazonia, with some phylogenetic insights

The karyotypes of Phyllostomus discolor and P. hastatus from Eastern Amazonia were studied by G-, C-, G/C sequential and Ag-NOR techniques. Both species presented 2n = 32, with the autosome complement composed of 30 bi-armed in P. discolor and 28 bi-armed plus 1 acrocentric in P. hastatus. In both species, the X chromosome is medium submetacentric while the Y is minute acrocentric. The present study found only one difference between the karyotypes of P. discolor and P. hastatus: the smallest autosome (pair 15) is bi-armed in discolor and acrocentric in hastatus, a result best explained by pericentric inversion. The C-banding revealed constitutive heterochromatin only at the centromeric regions of all chromosomes, with the NOR site located at the distal region of short arm of pair 15, in both species. The taxon P. discolor is considered primitive for genus Phyllostomus and the bi-armed form of pair 15 is the assumed primitive condition which, rearranged by a pericentric inversion originated the acrocentric from found in P. hastatus.

Chromosomal similarities and differences between tamarins, Leontopithecus and Saguinus (Platyrrhini, Primates)

The karyotypes of two taxa of genus Leontopithecus (rosalia and chrysomelas) are studied. Their G-, C- and NOR-banding patterns are compared with those of representatives of the genus Saguinus to determine chromosomal similarities and differences between the two genera and thus contribute to explaining phylogenetic relations between the tamarins. Leontopithecus, like the Saguinus, presents 2n = 46, 14 autosomes plus the Y acrocentric and 30 autosomes plus the X biarmed. No chromosomal rearrangement distinguishes the karyotypes of the representatives of genus Leontopithecus or genus Saguinus. The two genera are distinguished from each other by a paracentric inversion and pericentric inversions on at least four pairs of acrocentric autosomes, displacing the NORs of the small short arms in Leontopithecus to the proximal region of the long arms in Saguinus or vice versa. The tamarins are also distinguished by the distribution of noncentromeric constitutive heterochromatin. The data obtained indicate that the two tamarin genera are closely related chromosomally, suggesting that they probably originated from the same ancestral branch.

Radiation and speciation of spider monkeys, genus Ateles, from the cytogenetic viewpoint

The chromosomes of 22 animals of four subspecies of the genes Ateles (A. paniscus paniscus, A. p. chamek, A. belzebuth hybridus, and A. b. marginatus) were compared using G/C banding and NOR (nucleolar organizer region) staining methods. The cytogenetic data of Ateles in the literature were also used to clarify the phylogenetic relationships of the species and subspecies and to infer the routes of radiation and speciation of these taxa. Chromosomes 6 and 7 that showed more informative geographic variation and the apomorphic form 4/12, exclusively in A. p. paniscus, are the keys for understanding the evolution, radiation, and specification of the Ateles taxa. The ancestral populations of the genus originated in the southwestern Amazon Basin (the occurrence area of A. paniscus chamek) and spread in the Amazon Basin and westward, crossing the Andes and colonizing Central America and northwesternmost regions of South America. The evolutionary history of the northern South American taxa is interpreted using the model of biogeographical evolution postulated by Haffer [Science 185:131-137, 1969]. Ateles paniscus paniscus is the genetically most differentiated form and probably derives from A. belzebuth hybridus. Based on the karyotype differences, the populations of Ateles can be divided into four different groups. These findings indicate the necessity of a more coherent taxonomic arrangement for the taxa of Ateles.

Comparative chromosomal study of five taxa of genus Callithrix, group jacchus (Platyrrhini, Primates)

The karyotypes of four marmoset species of the Callithrix jacchus group (C. aurita, C. kuhlii, C. geoffroyi, and C. penicillata) were investigated. The patterns of G-, C-, and NOR-bands of these karyotypes were compared with those of C. jacchus, previously described, in order to clarify the taxonomic relationships of this species group. All species present 2n = 46, 14 uni- and 30 biarmed autosomes, a median size submetacentric X chromosome, and the same NOR-band patterns. No rearrangement or constitutive heterochromatic variation differentiate these species, which differ only in the morphology of the Y chromosome. The data obtained indicate that, from the chromosomal point stand, the marmoset species of C. jacchus group constitute a homogeneous clade.

Characterization of constitutive heterochromatin of Callithrix geoffroyi (Callitrichidae, Primates) by restriction enzymes and fluorochrome bands

The neotropical primate genus Callithrix comprises two groups of species, jacchus and argentata, which inhabit distinct geographical regions and manifest different fur coloration and constitutive heterochromatin (CH) markers in their karyotypes. In this investigation the CH of a representative of the jacchus group, Callithrix geoffroyi, was analysed using fluorochromes and restriction enzymes in situ. To clarify the source of the constitutive heterochromatin of both groups, the data obtained in the jacchus group were compared with those published in the argentata group obtained by the same techniques. The C-bands of C. geoffroyi (four specimens, 2n = 46) were centromeric in all chromosomes, and distally located in pairs 6 and 22. The Alu I, Hae III, Hin fI, Rsa I, Dde I, Mbo I, and Msp I restriction endonucleases and CMA3 and DAPI fluorochromes produced different bands, which allowed the characterization of four distinct types of constitutive heterochromatin in the C. geoffroyi genome. Several of these types of heterochromatin were present in the ancestor of the two groups of species, jacchus and argentata, while others originated after their cladogenesis.

Proposed chromosomal phylogeny for the South American primates of the Callitrichidae family (Platyrrhini)

Cytogenetic and cytotaxonomic studies (G, C, sequential G/C, and NOR banding) were performed on 110 specimens representing the four genera of South American primates of the family Callitrichidae: Cebuella (C. pygmaea), Callithrix, groups argentata (C. argentata, C. emiliae, C. chrysoleuca, C. humeralifera, C. mauesi), and jacchus (C. aurita, C. geoffroyi, C. jacchus, C. kuhli, C. penicillata), Leontopithecus (L. chrysomelas, L. rosalia), and Saguinus (S. midas midas, S. m. niger). Mitotic chromosomes are characterized, and the rearrangements distinguishing the karyotypes of the taxa are inferred from arm homologies. The results were then converted into numerical data and submitted to cladistic analysis. The following conclusions were achieved: 1) Five karyotypic classes were observed, which correspond to the five taxa studied. Differences between them are as follows: a) Cebuella (2n = 44, 10 acrocentrics, A + 32 bi-armed autosomes, bi) and the argentata group (2n = 44, 10A + 32bi) are different from each other due to a reciprocal translocation; b) both can be distinguished from the jacchus group (2n = 46, 14A + 30bi) by a centric fusion/fission rearrangement and a paracentric inversion; c) Leontopithecus (2n = 46, 14A + 30bi) and Saguinus (2n = 46, 14A + 30bi) differ from the jacchus group by a reciprocal translocation and three paracentric inversions; and d) Saguinus is different from the others by one paracentric inversion and pericentric inversions in at least four pairs of acrocentric autosomes. 2) The cladistic analysis separates Cebus (used as an outgroup) from the Callitrichidae groups, which forms a clade. Among the Callitrichidae, marmosets (Cebuella and Callithrix) form a sub-clade, Cebuella and the argentata group being more closely related to each other than both are to the jacchus group. Tamarins (Leontopithecus and Saguinus) are also quite close, so that if one was not derived from the other, they with the marmosets share a common ancestor. Among the tamarins, Leontopithecus is karyotypically closest to the marmosets, specifically to the jacchus group. 3) Based on the chromosome information and considering the possible direction of the evolutionary changes (primitivity or phyletic dwarfism hypothesis, previously advanced by other authors), it was possible to propose the ancestral karyotypes and to develop two alternatives for the origin, differentiation and dispersion of the callitrichid. Both proposals are plausible, but when the geographical distribution is considered, the phyletic dwarfism hypothesis seems to be the most probable.