An Insight into the Chromosomal Evolution of Lebiasinidae (Teleostei, Characiformes)

Abstract

Lebiasinidae fishes have been historically neglected by cytogenetical studies. Here we present a genomic comparison in eleven Lebiasinidae species, in addition to a review of the ribosomal DNA sequences distribution in this family. With that, we develop ten sets of experiments in order to hybridize the genomic DNA of representative species from the genus Copeina, Copella, Nannostomus, and Pyrrhulina in metaphase plates of Lebiasina melanoguttata. Two major pathways on the chromosomal evolution of these species can be recognized: (i) conservation of 2n = 36 bi-armed chromosomes in Lebiasininae, as a basal condition, and (ii) high numeric and structural chromosomal rearrangements in Pyrrhulininae, with a notable tendency towards acrocentrization. The ribosomal DNA (rDNA) distribution also revealed a marked differentiation during the chromosomal evolution of Lebiasinidae, since both single and multiple sites, in addition to a wide range of chromosomal locations can be found. With some few exceptions, the terminal position of 18S rDNA appears as a common feature in Lebiasinidae-analyzed species. Altogether with Ctenoluciidae, this pattern can be considered a symplesiomorphism for both families. In addition to the specific repetitive DNA content that characterizes the genome of each particular species, Lebiasina also keeps inter-specific repetitive sequences, thus reinforcing its proposed basal condition in Lebiasinidae.

Keywords: Neotropical fishes; comparative genomic hybridization; cytogenetics; karyotype; ribosomal DNA.

Figure 1

Map of the central portion of South America showing the Brazilian sample sites of Copeina guttata, Copella nattereri, Lebiasina melanoguttata, Nannostomus eques, N. marginatus, N. trifasciatus, N. unifasciatus, Pyrrhulina australis, Pyrrhulina aff. australis, P. brevis and P. semifasciata. The map was produced using the software QGis 3.4.4 (https://qgis.org), Inkscape 0.92 (https://inkscape.org), and Adobe Photoshop CC 2015 (San Jose, CA, USA).

Figure 2

Schematic representation of chromosomes of Lebiasinidae and Ctenoluciidae species, highlighting the position of 5S rDNA (green) and 18S rDNA (red). The small box highlights a sex chromosome system in Pyrrhulina semifasciata, while the bigger box highlights the Ctenoluciidae members. FISH data were taken from [3,4,5,6,7,24]. Letters correspond to the investigated genera: (a)—Boulengerella, (b)—Nannostomus, (c)—Lebiasina, (d)—Copeina, and (e)—Pyrrhulina.

Figure 3

Comparative genomic hybridization using the gDNA of Lebiasina melanoguttata, Copeina guttata, and Copella nattereri against the chromosomal background of Lebiasina melanoguttata. Genomic probes from L. melanoguttata and Copeina guttata hybridized against L. melanoguttata chromosomes (a–d). Genomic probes from L. melanoguttata and Copella nattereri hybridized against L. melanoguttata chromosomes (e–h). The first column (a,e): DAPI images (blue); second column (b,f): hybridization patterns using gDNA probe from L. melanoguttata; third column (c,g): hybridization patterns using gDNA probes from Copeina guttata and Copella nattereri, respectively; fourth column (d,h) merged images of both genomic probes and DAPI staining depicting the common regions in yellow. Scale bar = 5 µm.

Figure 4

Comparative genomic hybridization using the gDNA of Lebiasina melanoguttata and Pyrrhulina species against a chromosomal background of Lebiasina melanoguttata. Genomic probes from L. melanoguttata and P. australis hybridized against L. melanoguttata chromosomes (a–d). Genomic probes from L. melanoguttata and Pyrrhulina aff. australis hybridized against L. melanoguttata chromosomes (e–h). Genomic probes from L. melanoguttata and P. brevis hybridized against L. melanoguttata chromosomes (i–l). Genome from L. melanoguttata and P. semifasciata hybridized against L. melanoguttata chromosomes (m–p). The first column (a,e,I,m): DAPI images (blue); second column (b, f, j, and n): hybridization patterns using gDNA probe from L. melanoguttata; third column (c,g,k,o): hybridization patterns using gDNA probes from P. australis, Pyrrhulina aff. australis, P. brevis, and P. semifasciata, respectively; fourth column (d,h,l,p) merged images of both genomic probes and DAPI staining, depicting the shared regions in yellow. Scale bar = 5 µm.

Figure 5

Comparative genomic hybridization among Lebiasina melanoguttata and Nannostomus species. Genomic probes from L. melanoguttata and N. unifasciatus hybridized against L. melanoguttata chromosomes (a–d). Genomic probes from L. melanoguttata, and N. trifasciatus hybridized against L. melanoguttata chromosomes (e–h). Genomic probes from L. melanoguttata, and N. beckfordi hybridized against L. melanoguttata chromosomes (i–l). Genomic probes from L. melanoguttata and N. eques hybridized against L. melanoguttata chromosomes (m–p). Genomic probes from L. melanoguttata and N. marginatus hybridized against L. melanoguttata chromosomes (q–t). The first column (a,e,i,m,q): DAPI images (blue); second column (b,f,j,n,r): hybridization patterns using gDNA probe from L. melanoguttata; third column (c,g,k,o,s): hybridization patterns using gDNA probes from N. unifasciatus, N. trifasciatus, N. beckfordi, N. eques, and N. marginatus, respectively; fourth column (d,h,l,p,t) merged images of both genomic probes and DAPI staining depicting the shared regions in yellow. Scale bar = 5 µm.