Karyotype Diversity and Evolutionary Trends in Armored Catfish Species of the Genus Harttia (Siluriformes: Loricariidae)

Abstract

Most species of the genus Harttia inhabits the headwaters of small tributaries, but some species are restricted to the main channel of some rivers. This feature, combined with limited dispersal ability, leads to the formation of small isolated populations with reduced gene flow. Currently, there are 23 taxonomically defined and recognized species, and 17 of these are found in Brazil, distributed in several hydrographic basins. Despite this diversity, few chromosomal data for the species belonging to this genus are found in the literature. Thus, this study analyzed, by classical and molecular cytogenetics methodologies, the chromosomal diversity of this genus, to discuss the processes that are involved in the evolution and karyotype differentiation of the species of the group. Seven species of Harttia were analyzed: H. kronei, H. longipinna, H. gracilis, H. punctata, H. loricariformis, H. torrenticola, and H. carvalhoi. The chromosomal diversity found in these species includes different diploid and fundamental numbers, distinct distribution of several repetitive sequences, the presence of supernumerary chromosomes in H. longipinna and multiple sex chromosome systems of the type XX/XYY in H. carvalhoi and XXXX/XXY in H. punctata. Lastly, our data highlight the genus Harttia as an excellent model for evolutionary studies.

Multiple Sex Chromosomes and Evolutionary Relationships in Amazonian Catfishes: The Outstanding Model of the Genus Harttia (Siluriformes: Loricariidae)

“…Despite such great species diversity, cytogenetic studies are available for only eight of them, all from Brazilian Southern regions, with exception for Harttia punctata [ 3 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 ]. However, although still limited, the chromosome data are already enough to notice a conspicuous variation of the diploid number (2n) in the genus, ranging from 2n = 52♀/53♂ in H. carvalhoi [ 8 ] to 2n = 62♀♂ in H. absaberi [ 9 ].…”

“…However, although still limited, the chromosome data are already enough to notice a conspicuous variation of the diploid number (2n) in the genus, ranging from 2n = 52♀/53♂ in H. carvalhoi [ 8 ] to 2n = 62♀♂ in H. absaberi [ 9 ]. Chromosomal breaks and rearrangements as Robertsonian fusions, fissions, as well inversions were proposed to occur in the karyotype diversification of Harttia species [ 13 ]. In addition, two multiple XY-derived sex chromosome systems were also identified: ♀XX/♂XY 1 Y 2 in H. carvalhoi [ 8 ] and ♀X 1 X 1 X 2 X 2 /♂X 1 X 2 Y in H. punctata [ 12 ].…”

“…In recent years, a range of molecular cytogenetic investigations (e.g., repetitive DNA mapping based on fluorescence in situ hybridization (FISH), comparative genomic hybridization (CGH) and whole chromosome painting (WCP) has been applied in different fish groups, providing new insights into the evolutionary relationships among them [ 14 , 15 , 16 , 17 , 18 ]. However, the ribosomal genes are the only repetitive DNA class that has been analyzed in Harttia till now [ 3 , 8 , 12 , 13 ]. The rDNA mapping shows that the 18S sites presents a conserved pattern in number, with a single chromosome pair carrying these sequences in all analyzed species, but with variation in location and chromosome carrying them [ 13 ].…”

Chromosomal distribution of the retroelements Rex 1, Rex 3 and Rex 6 in species of the genus Harttia and Hypostomus (Siluriformes: Loricariidae)

“…Harttia is a genus of the subfamily Loricariinae that has 26 valid species (Fricke et al, 2019). Of these, only eight species present cytogenetic data (Alves et al, 2003;Kavalco et al, 2005;Centofante et al, 2006;Rodrigues, 2010;Blanco et al, 2012aBlanco et al, , 2013Blanco et al, , 2014Blanco et al, , 2017. The genus Harttia has conspicuous karyotype diversity, with diploid numbers (2n) ranging from 52 chromosomes in Harttia carvalhoi Miranda Ribeiro, 1939 females (Centofante et al, 2006) to 62 chromosomes in Harttia absaberi Oyakawa, Fichberg & Langeani, 2013 (cited as Harttia sp.…”

Comparative Cytogenetics Among Three Sympatric Hypostomus Species (Siluriformes: Loricariidae): An Evolutionary Analysis in a High Endemic Region

“…Chromosome variability at the intra-and interspecific level are detected in comparative cytogenetic studies [16][17][18] . In addition, recent cytogenetic data showed that evolutionary breakpoint regions clustered in repetitive DNA regions promoted genomic reshuffle and chromosome evolution in Loricariidae species [19][20][21][22][23][24][25] . Iguaçu River is an important tributary of Paraná River basin in the south region of Brazil and presents high endemism of its ichthyofauna due to the isolation caused by the formation of the Iguaçu waterfalls 22 Mya ago 26 .…”