Unrevealing the Karyotypic Evolution and Cytotaxonomy of Armored Catfishes (Loricariinae) with Emphasis in Sturisoma, Loricariichthys, Loricaria, Proloricaria, Pyxiloricaria, and Rineloricaria

Abstract

This study provides new insight into the chromosomal diversification in Loricariinae. We analyzed nine species from different Brazilian hydrographic basins, using conventional and molecular cytogenetic methods, aiming to understand the karyotypic diversification, and contribute with cytotaxonomic markers in this group considered one of the most diverse of Loricariidae. Our results evidenced a high karyotypic variability in diploid number (2n) ranging from 2n = 54 (Loricariichthys platymetopon and Loricariichthys anus), 2n = 60 (Rineloricaria reisi and Rineloricaria parva), 2n = 62 (Proloricaria prolixa), 2n = 64 (Loricaria cataphracta complex species), 2n = 66 (Sturisoma barbatum), and 2n = 68 (Pyxiloricaria menezesi). Different patterns of 18S and 5S ribosomal DNA (rDNA) were also identified, while slight divergences in heterochromatin distribution were observed. This high variability is probably related with independent events of Robertsonian translocations, pericentric inversions, and different mechanisms of rDNA sites dispersion (nonreciprocal translocation and transposable element [TEs] co-localization). In addition, our study provides a set of efficient chromosomal markers for the characterization of all analyzed species, and certainly, in future analyzes, will contribute as a useful cytotaxonomic tool in groups where the traditional taxonomy based on morphological data are not sufficient to clarify their relationship.

Chromosomal rearrangements and the first indication of an ♀X1X1X2X2/♂X1X2Y sex chromosome system in Rineloricaria fishes (Teleostei: Siluriformes)

“…On the other hand, the syntenic organization in the form of adjacent 5S and 18S rDNA sites on the chromosome pair 4 in R. teffeana is exceptional for the genus and, according to recent knowledge, it may serve as a species-specific marker. The syntenic arrangement of both rDNA classes has been otherwise previously observed in several loricariid species (Ayres- Alves et al, 2017;Blanco et al, 2017;Bueno et al, 2018;Favarato et al, 2016;Ferreira et al, 2014Ferreira et al, , 2017Pety et al, 2018;Takagui et al, 2020), andZiemniczak et al (2012) proposed that it may be a plesiomorphic condition for Loricariidae. Despite ample discussion, no potential functional significance of the syntenic arrangement of both rDNA classes has been convincingly demonstrated to date and so it seems that this feature is simply a by-product of genome dynamics (Roa & Guerra, 2015;Sochorová et al, 2018).…”

Cytogenetic Analysis of <b><i>Panaqolus tankei</i></b> Cramer &amp; Sousa, 2016 (Siluriformes, Loricariidae), an Ornamental Fish Endemic to Xingu River, Brazil

“…The current data about the karyotype formulae and repetitive DNA in situ localization show a wide variation in the karyotypes of different species of Ancistrini and Loricariinae tribes, even though the diploid number is considered conserved for some groups [Favarato et al, 2016;Ayres-Alves et al, 2017;Bueno et al, 2018;Pety et al, 2018;Takagui et al, 2020; present study]. Thus, inversion events play an important role in the karyotype evolution of this group.…”

“…Many species of the Ancistrini clade have shown synteny of 5S and 18S rDNA sites across lineages [Favarato et al, 2016;Ayres-Alves et al, 2017;Bueno et al, 2018;Pety et al, 2018], which currently is thought to display a homoplasic behavior among Loricariidae [Takagui et al, 2020], shared as well with its sister group Trichomycteridae [Bueno et al, 2018]. However, all karyotyped species of the Peckoltia clade demonstrated extensive variation in number and position of rDNA sites (5S and 18S).…”

“…debilittera, which has an additional chromosome with 18S sites [da Silva et al, 2014]. The presence of only 1 site of 18S rDNA in a metacentric or submetacentric chromosome pair is considered a primitive feature among Ancistrini, and the position and number of 5S rDNA sites show different patterns among this group and closely related tribes, as for instance Loricariinae [Artoni and Bertollo, 2001;Bueno et al, 2018;Ferreira et al, 2019b;Takagui et al, 2020]. For P. tankei, we found 2 sites of 5S rDNA in the same chromosome pair (8), one in the centromeric region and another in the distal region (Fig.…”

Adding New Pieces to the Puzzle of Karyotype Evolution in Harttia (Siluriformes, Loricariidae): Investigation of Amazonian Species

“…Notably, the diversification is associated with huge karyotype variability in Loricariidae, with diploid chromosome numbers (2n) ranging from 36 in Rineloricaria latirostris to 74 in Sturisoma cf. nigrirostrum [ 25 , 26 , 27 ]. Additionally, several types of sex chromosome systems including standard, derived, and multiple ones have been described for Loricariidae, as exemplified by Hypostomus genus with different ZW and XY cases [ 28 , 29 , 30 , 31 ], XX/XY, XX/X0, ZZ/ZW, and Z 1 Z 1 Z 2 Z 2 /Z 1 Z 2 W 1 W 2 in several Ancistrus species (reviewed in ref.…”