Comparative cytogenetics of two endangered leuciscine fish, Squalius aradensis and S. torgalensis (Teleostei, Cyprinidae), from the Iberian Peninsula

Abstract

In this study, the description of the karyotypes of the endangered chubs Squalius aradensis (Coelho, Bogutskaya, Rodrigues and Collares-Pereira, 1998) and Squalius torgalensis (Coelho, Bogutskaya, Rodrigues and Collares-Pereira, 1998) is presented by means of conventional (Giemsa-staining, Chromomycin A3 (CMA3)-fluorescence, Silver-impregnation (Ag-NORs)) and molecular (fluorescence in situ hybridization (FISH) with 18S rDNA probe) protocols. These endemic sister-species have an allopatric but adjacent distribution in the most southwestern part of the Iberian Peninsula. Diploid chromosome number was invariably 2n = 50 and karyotypes of both species were grossly similar, composed of metacentric and submetacentric elements with a reduced number of acrocentric pairs. Sequential staining using FISH with an 18S rDNA probe, CMA3 and Ag-NORs treatments revealed consistent positive signals located at the end of the short arms of a submetacentric chromosome pair, likely homologous in both species. While providing useful cytogenetic comparative data against other members of the genus Squalius Bonaparte, 1837, the work aimed to draw attention towards the conservation of two narrow-range and highly confined fish species.

Karyotype, C-band and NOR phenotype of Anatolian endemic fish Squalius anatolicus (Bogutskaya, 1997) (Teleostei, Leuciscidae)

“…Al-Sabti (1986) cephalus in those studies are different from S. anatolicus. In addition, in the karyotypes of S. alburnoides, S. lucumonis, S. aradensis and S. torgalensis were determined chromosome structure as distinct from S. anatolicus (Table 2) (Gromicho and Collares-Pereira, 2004;Rossi et al, 2012;Nabais et al, 2013).…”

Karyotype, C-banding and AgNORs of two endemic leuciscine fish, Pseudophoxinus crassus (Ladiges, 1960) and P. hittitorum Freyhof & Özulug, 2010 (Teleostei, Cyprinidae)

“…The number and location of NORs have been used as chromosome markers in fish cytotaxonomy ( Pereira et al 2012 , Rossi et al 2012 , Nabais et al 2013 ). The NORs located on a medium-sized SM chromosome pair corresponds to those observed in many of the leuciscines analyzed ( Bianco et al 2004 ).…”

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“…Furthermore, P. fahrettini shows similarity to European leuciscine species of the genera Leuciscus, Scardinius and Rutilus (Bianco et al, 2004) and to S. lucumonis (Rossi, Milana, Hett, & Tancioni, 2012) which has the Ag-NORs in the fourth sm chromosome. Also, P. evliyae shows similarity to S. aradensis and S. torgalensis that have the Ag-NORs in the seventh sm chromosome pair (Nabais, Rampin and Collares-Pereira, 2013).…”