Cytogenetic data on Ancistrus sp. (Siluriformes, Loricariidae) of the Paraguay River basin (MS) sheds light on intrageneric karyotype diversification

• Published in: Comparative cytogenetics Vol. 10; no. 4; pp. 625 - 636
• Main Authors: Prizon, Ana Camila, Borin-Carvalho, Luciana Andreia, Bruschi, Daniel Pacheco, Ribeiro, Marcos Otávio, Barbosa, Ligia Magrinelli, Ferreira, Greicy Ellen de Brito, Cius, Andréa, Zawadzki, Claudio Henrique, Portela-Castro, Ana Luiza de Brito
• Format: Journal Article
• Language: English
• Published: Bulgaria Pensoft Publishers 01.01.2016
• Subjects: Ancistrus; Banding; Biodiversity; Candidate species; Catfish; Chromosomes; Composition; Evolution; Evolutionary genetics; Fluorescence; Fluorescence in situ hybridization; Genomes; Heterochromatin; Heterogeneity; Homology; Nucleoli; Population studies; River basins; Rivers; Sex chromosomes; Silver; Silver nitrate; Species; Species diversity; Taxonomy; Paraguay River; rDNA; Ancistrini; cytotaxonomy; CMA3/DAPI; heterochromatin
• ISSN: 1993-0771; 1993-078X
• DOI: 10.3897/CompCytogen.v10i4.8532

Kner, 1854 is a diverse catfish genus, currently comprising 66 valid species, but karyotype data were recorded for 33 species, although only ten have their taxonomic status defined. Considerable karyotype diversity has been found within this genus, with 2n varying from 34 to 54 and structural variability including heteromorphic sex chromosomes. In many cases, uncertainty on the taxonomic status of the study populations hampers reliable interpretation of the complex chromosomal evolutionary history of the group. This study aims to present the first karyotype data for a population of the sp. collected in Criminoso stream (tributary of the Paraguay River Basin, Mato Grosso do Sul, Brazil) in which a combination of different chromosomal markers was used and results integrated in broad discussion on karyotype evolution in the genus. The specimens presented 2n=42 with 18m+16sm+8st and a single NOR revealed by silver nitrate and fluorescence hybridization (FISH) with 18S rDNA probe, located in pair No. 10. Clusters of 5S rDNA were located in the pericentromeric region of three chromosomes: pair No. 1 (metacentric) and one of the homologues of the nucleolar pair No. 10. Heterogeneity in the molecular composition of the heterochromatin was confirmed by the association of C-banding and fluorochrome CMA /DAPI-staining. Exploring the differential composition of constitutive heterochromatin in may provide an important perspective to understand genome organization and evolution within this group. Our data reinforce the chromosomal diversity present in genus and we discuss the potential sources these variation. The karyotype structure of sp. "Criminoso stream" appears to be consistent with the existence of a new candidate species.