Polymorphisms of the nucleolus organizing regions in Loricaria cataphracta (Siluriformes, Loricariidae) of the upper Paraguay River basin indicate an association with transposable elements

Abstract

ABSTRACT.A cytogenetic analysis of Loricaria cataphracta revealed a diploid number of 2n = 64 chromosomes, distributed as 12 metacentric + 8 submetacentric + 2 subtelocentric + 42 acrocentric, with a fundamental number of 86. Analysis of the nucleolus organizing region (NOR) using silver nitrate impregnation and fluorescence in situ hybridization (18S rDNA probe) techniques showed intra-population chromosomal polymorphism that could be classified into five different patterns

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

“…For the latter two species, the authors proposed that fusion events are the most plausible explanation for the observed structural and numerical polymorphisms, since the increase in the number of biarmed chromosomes is correlated with the decrease in 2n. In R. lanceolata and R. latirostris, this hypothesis was confirmed by the presence of interstitial telomeric sequences (ITSs) or other repetitive sequences in the predicted fusion points(Giuliano-Caetano, 1998;Porto, Gindri et al, 2014;Glugoski et al, 2022).The presence of monoarmed chromosomes is a common feature in Rineloricaria and the karyotype of R. teffeana studied herein also fits this pattern. However, the exclusive presence of acrocentric chromosomes combined with low 2n is exceptional and has not yet been reported for the genus.…”

“…For the latter two species, the authors proposed that fusion events are the most plausible explanation for the observed structural and numerical polymorphisms, since the increase in the number of biarmed chromosomes is correlated with the decrease in 2 n . In R. lanceolata and R. latirostris , this hypothesis was confirmed by the presence of interstitial telomeric sequences (ITSs) or other repetitive sequences in the predicted fusion points (Giuliano‐Caetano, 1998; Porto, Gindri et al ., 2014; Glugoski et al ., 2022).…”

“…The karyotype differentiation of Rineloricaria spp. has been shaped by various types of chromosomal rearrangements among which centric fusions and fissions were notably common (Artoni & Bertollo, 2001; Giuliano‐Caetano, 1998; Glugoski et al ., 2022; Porto, Vieira et al ., 2014;Porto, Gindri et al ., 2014; Primo et al ., 2017; Rosa et al ., 2012). A comparably high rate of karyotype change has also been reported for several other representatives of the subfamily Loricariinae, with the striking example of the armoured catfish genus Harttia (Blanco et al ., 2014, 2017; Deon et al ., 2020, 2022a, 2022b; Sassi et al ., 2020, 2021).…”

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

“…Considering this restricted distribution to the Amazonian system, we also assume that there was a mistake in the identification of populations previously diagnosed as L. cataphracta, coming from the Coxim River (Upper Paraguay river). 33 When compared with L. simillima, such specimens share some characteristics (e.g., 2n = 64, heterochromatin pattern); however, they exhibit a marked numerical and structural polymorphism of NOR sites. This is a condition until then, exclusive to this population, which can be interpreted as (1) a population variation; (2) an error in taxonomic identification, these specimens may be other species that occur in the Coxim River basin (e.g., Loricaria apeltogaster or Loricaria coximensis); or (3) an undescribed species that is morphologically related to the L. cataphracta complex.…”

“…28 Moreover, this group has supernumerary chromosomes, 24,35,40 differentiated sex chromosomes, 23,25,30 and intrapopulational polymorphisms in diploid number and karyotypic formulas [42][43][44] and in distribution of ribosomal DNA (rDNA) sites. 33 This study consists of the first review and comparative analysis involving species of Loricariinae from different Brazilian watersheds. Our study aimed to hypothesize the chromosome evolution as well as to fill in the gap of cytotaxonomic knowledge to clarify the relationships of conflicted groups in Loricariini tribe.…”