birdchromosomedatabase) we have compiled data on the chromosome numbers of 1,067 bird species and chromosome painting data on 96 species. We found considerable variation in the diploid numbers, which ranged from 40 to 142, although most (around 50%) of the species studied up to now have between 78 and 82 chromosomes. Despite its importance for cytogenetic research, chromosome painting has been applied to less than 1% of all bird species. The BCD will enable researchers to identify the main knowledge gaps in bird cytogenetics, including the most under-sampled groups, and make inferences on chromosomal homologies in phylogenetic studies. © 2020 S. Karger AG, BaselDatabases present a valuable source of information for research on a wide range of topics, including species inventories, cytogenetics of some key groups, chromosomal mapping of rDNA, and even complete genomic sequences [Peruzzi and Bedini, 2014;Jarvis et al., 2015;Cardoso et al., 2018;Gill and Donsker, 2018; Paresque et al., AbstractBird chromosomes, which have been investigated scientifically for more than a century, present a number of unique features. In general, bird karyotypes have a high diploid number (2n) of typically around 80 chromosomes that are divided into macro-and microchromosomes. In recent decades, FISH studies using whole chromosome painting probes have shown that the macrochromosomes evolved through both inter-and intrachromosomal rearrangements. However, chromosome painting data are available for only a few bird species, which hinders a more systematic approach to the understanding of the evolutionary history of the enigmatic bird karyotype. Thus, we decided to create an innovative database through compilation of the cytogenetic data available for birds, including chromosome numbers and the results of chromosome painting with chicken ( Gallus gallus ) probes. The data were obtained through an extensive literature review, which focused on cytogenetic studies published

Birds are characterized by a low proportion of repetitive DNA in their genome when compared to other vertebrates. Among birds, species belonging to Piciformes order, such as woodpeckers, show a relatively higher amount of these sequences. The aim of this study was to analyze the distribution of different classes of repetitive DNA—including microsatellites, telomere sequences and 18S rDNA—in the karyotype of three Picidae species (Aves, Piciformes)—Colaptes melanochloros (2n = 84), Colaptes campestris (2n = 84) and Melanerpes candidus (2n = 64)–by means of fluorescence in situ hybridization. Clusters of 18S rDNA were found in one microchromosome pair in each of the three species, coinciding to a region of (CGG)10 sequence accumulation. Interstitial telomeric sequences were found in some macrochromosomes pairs, indicating possible regions of fusions, which can be related to variation of diploid number in the family. Only one, from the 11 different microsatellite sequences used, did not produce any signals. Both species of genus Colaptes showed a similar distribution of microsatellite sequences, with some difference when compared to M. candidus. Microsatellites were found preferentially in the centromeric and telomeric regions of micro and macrochromosomes. However, some sequences produced patterns of interstitial bands in the Z chromosome, which corresponds to the largest element of the karyotype in all three species. This was not observed in the W chromosome of Colaptes melanochloros, which is heterochromatic in most of its length, but was not hybridized by any of the sequences used. These results highlight the importance of microsatellite sequences in differentiation of sex chromosomes, and the accumulation of these sequences is probably responsible for the enlargement of the Z chromosome.

The order Charadriiformes comprises three major clades: Lari and Scolopaci as sister group to Charadrii. Until now, only three Charadriiformes species have been studied by chromosome painting: Larus argentatus (Lari), Burhinus oedicnemus and Vanellus chilensis (Charadrii). Hence, there is a lack of information concerning the third clade, Scolapaci. Based on this, and to gain a better understanding of karyotype evolution in the order Charadriiformes, we applied conventional and molecular cytogenetic approaches in a species belonging to clade Scolopaci-the wattled jacana (Jacana jacana)-using Gallus gallus and Zenaida auriculata chromosome-specific probes. Cross-species evaluation of J. jacana chromosomes shows extensive genomic reshuffling within macrochromosomes during evolution, with multiple fission and fusion events, although the diploid number remains at high level (2n=82). Interestingly, this species does not have the GGA7-8 fusion, which was found in two representatives of Charadrii clade, reinforcing the idea that this fusion may be exclusive to the Charadrii clade. In addition, it is shown that the chromosome evolution in Charadriiformes is complex and resulted in species with typical and atypical karyotypes. The karyotypic features of Scolopaci are very different from those of Charadrii and Lari, indicating that after divergence, each suborder has undergone different chromosome rearrangements.

As in many other bird groups, data on karyotype organization and distribution of repetitive sequences are also lacking in species belonging to the family Hirundinidae. Thus, in the present study, we analyzed the karyotypes of 3 swallow species (Progne tapera, Progne chalybea, and Pygochelidon cyanoleuca) by Giemsa and AgNOR staining, C-banding, and FISH with 11 microsatellite sequences. The diploid chromosome number was 2n = 76 in all 3 species, and NORs were observed in 2 chromosome pairs each. The microsatellite distribution pattern was similar in both Progne species, whereas P. cyanoleuca presented a distinct organization. These repetitive DNA sequences were found in the centromeric, pericentromeric, and telomeric regions of the macrochromosomes, as well as in 2 interstitial blocks in the W chromosome. Most microchromosomes had mainly telomeric signals. The Z chromosome displayed 1 hybridization signal in P. tapera but none in the other species. In contrast, the W chromosome showed an accumulation of different microsatellite sequences. The swallow W chromosome is larger than that of most Passeriformes. The observed enlargement in chromosome size might be explained by these high amounts of repetitive sequences. In sum, our data highlight the significant role that microsatellite sequences may play in sex chromosome differentiation.

The distribution of 45S rDNA cluster in avian karyotypes varies in different aspects, such as position, number of bearer chromosomes, and bearers being macro-or microchromosomes. The present study investigated the patterns of variation in the 45S rDNA-bearer chromosomes of birds in order to understand the evolutionary dynamics of the cluster configuration and its contribution to the evolution of bird karyotypes. A total of 73 bird species were analyzed, including both published data and species for which rDNA-FISH was conducted for the first time. In most birds, the 45S rDNA clusters were located in a single pair of microchromosomes. Hence, the location of 45S rDNA in macrochromosomes, observed only in Neognathae species, seems to be a derived state, probably the result of chromosomal fusion between microchromosomes and distinct macrochromosomes. Additionally, the 45S rDNA was observed in multiple microchromosomes in different branches of the bird phylogeny, suggesting recurrence of dispersion processeses, such as duplications and translocations. Overall, this study indicated that the redistribution of the 45S rDNA sites in bird chromosomes followed different evolutionary trajectories with respect to each lineage of the class Aves.

Trogons are forest birds with a wide distribution, being found in Africa, Asia, and America, and are included in the order Trogoniformes, family Trogonidae. Phylogenetic studies using molecular data have not been able to determine the phylogenetic relationship among the different genera of trogons. So far, no cytogenetic data for these birds exist. Hence, the aim of this study was to characterize the karyotype of Trogon surrucura surrucura by means of classical and molecular cytogenetics. We found a diploid chromosome number of 2n = 82, similar to most birds, with several derived features compared to chicken and the putative ancestral avian karyotype. T. s. surrucura showed 3 pairs of microchromosomes bearing 18S rDNA clusters. The Z and W sex chromosomes were of similar size but could readily be identified by morphological differences. Using chromosome painting with whole chromosome probes from Gallus gallus and Leucopternis albicollis, we found that the chromosomes homologous to chicken chromosomes 2 and 5 correspond to 2 different pairs in T. s. surrucura and L. albicollis, due to the occurrence of centric fissions. Paracentric inversions were detected in the segment homologous to chicken chromosome 1q, and we confirmed the recurrence of breakpoints when our results were compared to other species of birds already analyzed by FISH or by in silico genome assembly.

Penguins are classified in the order Sphenisciformes into a single family, Spheniscidae. The genus Pygoscelis Wagler, 1832, is composed of three species, Pygoscelis antarcticus Forster, 1781, P. papua Forster, 1781 and P. adeliae Hombron & Jacquinot, 1841. In this work, the objective was to describe and to compare the karyotypes of Pygoscelis penguins contributing genetic information to Sphenisciformes. The metaphases were obtained by lymphocyte culture, and the diploid number and the C-banding pattern were determined. P. antarcticus has 2n = 92, P. papua 2n = 94 and P. adeliae exhibited 2n = 96 in males and 2n = 95 in females. The difference of diploid number in P. adeliae was identified as a multiple sex chromosome system where males have Z1Z1Z2Z2 and females Z1Z2W. The C-banding showed the presence of a heterochromatic block in the long arm of W chromosome and Z2 was almost entirely heterochromatic. The probable origin of a multiple system in P. adeliae was a translocation involving the W chromosome and the chromosome ancestral to Z2. The comparison made possible the identification of a high karyotype homology in Sphenisciformes which can be seen in the conservation of macrochromosomes and in the Z chromosome. The karyotypic divergences in Pygoscelis are restricted to the number of microchromosomes and W, which proved to be highly variable in size and morphology. The data presented in this work corroborate molecular phylogenetic proposals, supporting the monophyletic origin of penguins and intraspecific relations.

Domestic buffaloes are divided into two group based on cytogenetic characteristics and habitats: the “river buffaloes” with 2n = 50 and the “swamp buffaloes”, 2n = 48. Nevertheless, their hybrids are viable, fertile and identified by a 2n = 49. In order to have a better characterization of these different cytotypes of buffaloes, and considering that NOR-bearing chromosomes are involved in the rearrangements responsible for the karyotypic differences, we applied silver staining (Ag-NOR) and performed fluorescent in situ hybridization (FISH) experiments using 18S rDNA as probe. Metaphases were obtained through blood lymphocyte culture of 21 individuals, including river, swamp and hybrid cytotypes. Ag-NOR staining revealed active NORs on six chromosome pairs (3p, 4p, 6, 21, 23, 24) in the river buffaloes, whereas the swamp buffaloes presented only five NOR-bearing pairs (4p, 6, 20, 22, 23). The F1 cross-breed had 11 chromosomes with active NORs, indicating expression of both parental chromosomes. FISH analysis confirmed the numerical divergence identified with Ag-NOR. This result is explained by the loss of the NOR located on chromosome 4p in the river buffalo, which is involved in the tandem fusion with chromosome 9 in this subspecies. A comparison with the ancestral cattle karyotype suggests that the NOR found on the 3p of the river buffalo may have originated from a duplication of ribosomal genes, resulting in the formation of new NOR sites in this subspecies.