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.

Karyotype, evolution and phylogenetic reconstruction in Micronycterinae bats with implications for the ancestral karyotype of Phyllostomidae.

BACKGROUND: The Micronycterinae form a subfamily of leaf-nosed bats (Phyllostomidae) that contains the genera Lampronycteris Sanborn, 1949, and Micronycteris Gray, 1866 (stricto sensu), and is characterized by marked karyotypic variability and discrepancies in the phylogenetic relationships suggested by the molecular versus morphological data. In the present study, we investigated the chromosomal evolution of the Micronycterinae using classical cytogenetics and multidirectional chromosome painting with whole-chromosomes probes of Phyllostomus hastatus and Carollia brevicauda. Our goal was to perform comparative chromosome mapping between the genera of this subfamily and explore the potential for using chromosomal rearrangements as phylogenetic markers. RESULTS: The Micronycterinae exhibit great inter- and intraspecific karyotype diversity, with large blocks of telomere-like sequences inserted within or adjacent to constitutive heterochromatin regions. The phylogenetic results generated from our chromosomal data revealed that the Micronycterinae hold a basal position in the phylogenetic tree of the Phyllostomidae. Molecular cytogenetic data confirmed that there is a low degree of karyotype similarity between Lampronycteris and Micronycteris specimens analyzed, indicating an absence of synapomorphic associations in Micronycterinae. CONCLUSIONS: We herein confirm that karyotypic variability is present in subfamily Micronycterinae. We further report intraspecific variation and describe a new cytotype in M. megalotis. The cytogenetic data show that this group typically has large blocks of interstitial telomeric sequences that do not appear to be correlated with chromosomal rearrangement events. Phylogenetic analysis using chromosome data recovered the basal position for Micronycterinae, but did not demonstrate that it is a monophyletic lineage, due to the absence of common chromosomal synapomorphy between the genera. These findings may be related to an increase in the rate of chromosomal evolution during the time period that separates Lampronycteris from Micronycteris.

Cryopreservation of domestic cat (Felis catus) ovarian tissue: Comparison of two vitrification methods.

We aimed to evaluate the effect of two vitrification methods on the morphology and functionality of vitrified feline preantral follicles. Feline ovarian tissue was vitrified with EG + trehalose combined or not with dimethyl sulphoxide (DMSO), using two different techniques (open or closed systems). Morphology, developmental capacity and mRNA expression of markers for follicle survival and quality were assessed before and after in vitro culture (IVC). Both vitrification and culture media were serum-free. Vitrification of feline ovarian tissue from five adult domestic cats was performed with EG + trehalose combined or not with DMSO. Two systems were used: the open system solid-surface vitrification (SSV) and the closed system ovarian tissue cryosystem (OTC). Histological analysis of follicle integrity showed that the percentages of normal follicles in previously vitrified ovarian fragments decreased after 7 days of in vitro culture (IVC), independently of the protocol used. Although follicular activation was observed by Ki-67 labelling, this was accompanied by extensive follicular degeneration as detected by a 3-4-fold decrease in follicular density. Remarkable follicle activation was observed in the ovarian tissue vitrified using OTC and subjected to IVC, probably due to a higher rate of degeneration of developing follicles. Even with such follicular loss, the results are promising for the combination of EG + DMSO + trehalose in a serum-free medium when applying the SSV method, with this approach resulting in the highest rates of normal developing follicles (19%) after 7 days IVC, together with granulosa cells proliferating at the same rate observed in fresh tissue.

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.

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.

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.

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.

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.

Neo-XY body: an analysis of XY1Y2 meiotic behavior in Carollia (Chiroptera, Phyllostomidae) by chromosome painting.

Classical and molecular cytogenetic analyses of mitotic and meiotic cells were performed on two species of Carollia from the family Phyllostomidae (Chiroptera), which have an XX/XY(1)Y(2) sex determination system. Our results show that the species Carollia perspicillata and Carollia brevicauda have the same Xq-autosome translocation (neo-X). Using multicolor FISH we observed different levels of condensation of the original X and Y chromosomes when compared to the translocated autosomal segment, a likely consequence of the nucleolar organizer region blocking spreading of inactivation to the autosomal region of the neo-X. The use of chromosome painting showed the behavior of the sex chromosome trivalent--here called the 'neo-XY body'--in meiosis. We compared the variation between the condensation of the original X and Y and the autosome-sex chromosome axis and described the pairing between the original X-Y segments (pseudoautosomal region) and the XY(2) homologous segments, suggesting genetic activity of the latter during meiosis.

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.

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.

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.