Karyotype and genome size of Iberochondrostoma almacai (Teleostei, Cyprinidae) and comparison with the sister-species I. lusitanicum

Abstract

This study aimed to define the karyotype of the recently described Iberian endemic Iberochondrostoma almacai, to revisit the previously documented chromosome polymorphisms of its sister species I.lusitanicum using C-, Ag-/CMA3 and RE-banding, and to compare the two species genome sizes. A 2n = 50 karyotype (with the exception of a triploid I.lusitanicum specimen) and a corresponding haploid chromosome formula of 7M:15SM:3A (FN = 94) were found. Multiple NORs were observed in both species (in two submetacentric chromosome pairs, one of them clearly homologous) and a higher intra and interpopulational variability was evidenced in I.lusitanicum. Flow cytometry measurements of nuclear DNA content showed some significant differences in genome size both between and within species: the genome of I. almacai was smaller than that of I.lusitanicum (mean values 2.61 and 2.93 pg, respectively), which presented a clear interpopulational variability (mean values ranging from 2.72 to 3.00 pg). These data allowed the distinction of both taxa and confirmed the existence of two well differentiated groups within I. lusitanicum: one that includes the populations from the right bank of the Tejo and Samarra drainages, and another that reunites the southern populations. The peculiar differences between the two species, presently listed as “Critically Endangered”, reinforced the importance of this study for future conservation plans.

Cytogenetic studies on six species of the leuciscine genusPseudophoxinusBleeker, 1860 (Teleostei, Cyprinidae)

“…In addition, multiple NORs are considered as a derived character (Valic et al 2010). These NORs have been observed in some Anatolian leuciscine species (A. marmid (Gaffaroğlu et al 2006), P. firati (Karasu et al 2011) and P. elizavetae (Gaffaroğlu et al 2014)) and also in several European leuciscine species (Boron 2001;Monteiro et al 2009;Pereira et al 2009) such as P. battalgilae, P. evliyae and P. maeandri.…”

Cytogenetic survey of species of two distinct genera of Iberian nases (Cyprinidae, Leuciscinae) that hybridize extensively in nature. I. Evidence of a similar and conserved chromosome pattern with some few species-specific markers at macro-structural level

“…Despite the apparent constancy observed to date in the sub-family, multichromosomal locations (multiple NORs) have been also described in Eurasian and NorthAmerican species and considered a derived character. In European species they were only reported for Iberochondrostoma lusitanicum (Rodrigues and Collares-Pereira 1996;Collares-Pereira and Ráb 1999), Iberochondrostoma almacai (Monteiro et al 2009), Eupallasella perenurus (Boron et al 1997;Boron 2001), Phoxinus phoxinus (Boron 2001) and more recently for the female specimen of Parachondrostoma arrigonis (Kalous et al 2008) and for Leuciscus leuciscus (Boron et al 2009), as well as for the three now studied species A. oligolepis, P. duriense (see also Gante et al 2004) and P. polylepis. Thus, the species of the new Iberian Chondrostoma genera defined by Robalo et al (2007) although apparently retaining the common leuciscin karyotype pattern including an ubiquitous middle-size sm NOR-bearing pair of chromosomes, exhibit more differentiated NOR-phenotypes demanding an in-depth investigation with molecular tools (Ráb et al 2007;Boron et al 2009) in a wider range of congeneric taxa.…”

Chromosomes of Iberian Leuciscinae (Cyprinidae) Revisited: Evidence of Genome Restructuring in Homoploid Hybrids Using Dual-Color FISH and CGH

“…Besides basic Giemsa-stained chromosome counts and karyotype morphology [Collares-Pereira, 1985;Ráb and Collares-Pereira, 1995;Collares-Pereira et al, 1998], silver and chromomycin-A 3 bandings added little information to the differentiation of the genomes of these cyprinid fish [Rodrigues and Collares-Pereira, 1996;Gante et al, 2004;Gromicho and Collares-Pereira, 2004;Gromicho et al, 2006a;Monteiro et al, 2009;Pereira et al, 2009]. On one hand, results were consistent with the overall karyotypic pattern of the subfamily, whereas suggesting some degree of divergence by the presence of more than one chromosome pair bearing the NORs.…”

“…The karyotype structure in this group varies between 5-7 metacentric, 15-18 submetacentric and 2-4 subtelo-to acrocentric chromosome pairs and fundamental number ranges from 92 to 96 ( fig. 1 e) [Collares- Pereira, 1985;Ráb and Collares-Pereira, 1995;Collares-Pereira et al, 1998;Gromicho et al, 2006a;Monteiro et al, 2009;Nabais et al, 2013].…”

“…1 e) (e.g. large subtelo-to acrocentric and large submetacentric chromosomes) [Monteiro et al, 2009;Pereira et al, 2009]. …”