Abstract Cytogenetic characterization was performed on three wandering spiders: Ctenus amphora Mello-Leitão, 1930, C. crulsi Mello-Leitão, 1930 and C. villasboasi Mello-Leitão, 1949. The three species had similar karyotypes, with 2n = 28 (26 + X1X20) in males, with sex chromosomes exhibiting positive heteropicnosis in meiotic cells. 18S rDNA mapping revealed gene sites at the terminal region of one chromosomal pair for all species, with one C. crulsi individual, showing markings in two pairs. C. villasboasi showed markers only in the pachytene phase. The distribution pattern of constitutive heterochromatin was found to be characteristic for the genus, with markings in the centromeric region of all chromosomes, suggesting an acrocentric morphology for all chromosomes of the three analysed species. The results support the fusion of sex chromosomes as an evolutionary tendency for this spider group.

Cytogenetic analysis of the Amazon stingless bee Melipona seminigra merrillae, by conventional Giemsa staining and C-banding, revealed a different chromosome number for Melipona: 2n = 22 for females and diploid drones while the haploid drones present n = 11. There is no evidence of B chromosomes. This result contrasts with previous studies, in which the chromosome number of 19 Melipona species was determined as 2n = 18 for females and n = 9 for haploid males. Based on cytogenetic information available for other Melipona species, we propose that M. s. merrillae has a more derived diploid number. This indicates that chromosome number is not a conservative characteristic within the genus as previously thought. Cytogenetic data for stingless bees are scarce, especially in Amazon region. Additional studies will be very important in order to promote Melipona karyoevolution discussion and consequently a taxonomy review.

Karyotypes of six cichlid species of the genus Crenicichla were investigated. The species C. cincta, C. inpa, C. reticulata, C. lugubris, and C. cf. johanna were collected from Amazon basin, and C. britskii was collected from the Paraná-Paraguai basin. All of the analysed species showed 2n = 48 chromosomes; however, C. cincta, C. lugubris, C. cf. johanna, and C. britskii had a karyotype formula of 8M-SM+40ST-A, FN = 56, while C. inpa and C. reticulata exhibited the formula 6M-SM+42ST-A, FN = 54. Analysis of active Ag-NORs revealed two NOR-bearing chromosomes in all species; however, theses cistrons were located on different chromosome pairs and/or in different chromosome locations in each species. This condition bears evolutionary significance, since it is the main chromosome marker of the process of karyotypic evolution among the species of the genus Crenicichla. In general, C-banding revealed a similar constitutive heterochromatin pattern in all species, although it was possible to detect some features that led us to infer that Crenicichla also presents a species-specific heterochromatin pattern.

Comparative cytogenetic analyses of hatchetfishes Carnegiella marthae and Carnegiella strigata (Gasteropelecidae) from the Rio Negro basin were performed using conventional Giemsa staining, silver (Ag) -staining and C-banding. The diploid chromosome numbers of both species equaled 2n = 50 but their karyotypes were distinct. We found evidence for sex chromosomes in C. marthae since karyotype of males presented 20 M + 12 SM + 4 ST + 14 A and ZZ ST chromosomes while the females presented 20 M + 12 SM + 4 ST + 14 A and ZW ST chromosomes of distinct size. Conversely, C. strigata presented 4 M + 4 SM + 2 ST + 40 A chromosomes without sex chromosome heteromorphism. Karyotypes of both species had two NOR-bearing SM chromosomes of distinct size indicating the presence of multiple NOR phenotypes. The sex chromosome pair had specific C-banding pattern allowing identification of both Z and W. This heteromorphic system has previously been described for the gasteropelecids.

Quatro populações de Astyanax aff. fasciatus do alto rio Tibagi (município de Ponta Grossa, Paraná, Brasil) foram citogeneticamente e morfometricamente analisadas. Os dados citogenéticos mostram a ocorrência de distintos cariótipos (citótipos), aqui nomeados citótipo A, com 2n=48 (6m+18sm+14st+10a), citótipo B, com 2n=50 (8m+18sm+14st+10a) e citótipo C, com 2n=50 cromossomos (8m+18sm+14st+10a). O padrão de distribuição da heterocromatina constitutiva foi muito similar entre os citótipos A e B, mas mostrou-se divergente em relação ao citótipo C. Citótipos distintos podem ocorrer em simpatria na região do alto rio Tibagi, com exceção da amostra da Furna 2, a qual apresenta somente o citótipo A exclusivamente. Além disso, um exemplar com 2n=49 cromoossomos (7m+18sm+14st+10a) foi também encontrado e, pelas características apresentadas, pode ser uma conseqüência de um raro evento de hibridização entre os citótipos A e B. As análises morfométricas de variáveis canônicas indicam um isolamento consistente da amostra da Furna 2 enquanto as demais amostras analisadas se apresentam sobrepostas indicando um possível fluxo gênico ou evento de isolamento recente. Este modelo aponta para um complexo de espécies crípticas na região estudada.

Four populations of Astyanax aff. fasciatus of the upper rio Tibagi (municipal district of Ponta Grossa, Paraná State, Brazil), had their karyotypes and morphometry analyzed. The cytogenetic data show the occurrence of distinct karyotypes (cytotypes), here named cytotype A, with 2n=48 chromosomes (6m+18sm+14st+10a), cytotype B, with 2n=50 chromosomes (8m+18sm+14st+10a) and cytotype C, with 2n=50 chromosomes (8m+18sm+14st+10a). The distribution pattern of the constitutive heterochromatin was very similar between cytotypes A and B, but diverged in relation to cytotype C. Distinct cytotypes may occur in sympatry in the upper rio Tibagi region, with the exception of the Furna 2 sample, which presents cytotype A exclusively. In addition, a specimen with 2n=49 chromosomes (7m+18sm+14st+10a) was also found and, by the characteristics presented, may be a consequence of a rare hybridization event between cytotypes A and B. The morphometric analyses of canonical variates indicate a consistent isolation of the Furna 2 sample, while the other samples seem to be superimposed, indicating a possible gene flow or even a recent isolation event. This model points to a probable complex of cryptic species in the studied region.

Morphological and chromosomal markers were used to infer the structure and genetic variability of a population of fish of the genus Astyanax, geographically isolated at sinkhole 2 of Vila Velha State Park, Paraná, Brazil. Two morphotypes types were observed, the standard phenotype I and phenotype II which showed an anatomical alteration probably due to an inbreeding process. Fluctuating asymmetry (FA) analysis of different characters showed low levels of morphological variation among the population from sinkhole 2 and in another population from the Tibagi river (Paraná, Brazil). The Astyanax karyotype was characterized in terms of chromosomal morphology, constitutive heterochromatin and nucleolar organizer regions. Males and females presented similar karyotypes (2n=48, 6M+18SM+14ST+10A) with no evidence of a sex chromosome system. One female from sinkhole 2 was a natural triploid with 2n=3x=72 chromosomes (9M+27SM+21ST+15A). The data are discussed regarding the maintenance of population structure and their evolutionary importance, our data suggesting that Astyanax from the Vila Velha State Park sinkhole 2 is a recently isolated population.