Diversity and chromosomal evolution in the genus Ancistrus Kner, 1854 (Loricariidae: Ancistrini) from three hydrographic basins of Mato Grosso State, Brazil

Abstract

Cytogenetic analyses were carried out in 117 specimens of seven species of the genus Ancistrus from three hydrographic in Mato Grosso State: Paraguay, Araguaia-Tocantins and Amazon basins. Conventional cytogenetic techniques were used to obtain mitotic chromosomes. C-banding was performed to detect heterochromatic regions and silver nitrate staining was used to identify nucleolar organizer regions (Ag-NORs). The counted and paired chromosomes revealed diploid numbers ranging from 2n = 40 to 2n = 54 with karyotype formulae varying from FN = 80 to FN = 86. Single marks in distinct chromosomes identified the nucleolar organizer regions. The constitutive heterochromatin was scarce in the diploid number from 2n = 50 to 2n = 54 and conspicuous blocks were observed in a single species with 2n = 40 chromosomes. These data corroborate the hypotheses of reduction of diploid number in species with derived features such as presence of sex chromosomes and polymorphisms, besides allowing inferences about the evolutionary mechanisms and the ancestor karyotype that favored the diversification of this important genus in the tribe Ancistrini. Foram realizadas análises citogenéticas de 117 espécimes do gênero Ancistrus de três bacias hidrográficas do estado de MatoGrosso: Paraguai, Araguaia-Tocantins e Amazônica, utilizando as técnicas de citogenética convencional para obtenção de cromossomos mitóticos, visualização de regiões heterocromáticas e regiões organizadoras de nucléolos. Os cromossomos pareados revelaram uma variação no número diploide de 2n = 40 a 2n = 54 e número fundamental de NF = 80 a NF = 86. As regiões organizadoras de nucléolos foram evidenciadas em um único par de cromossomos para todas as espécies e a heterocromatina é escassa nas espécies com números diploides elevados (2n = 50 a 2n = 54). Os blocos heterocromáticos mais evidentes foram observados nos pares portadores das AgRONs e em cromossomos da espécie com 2n = 40. Estes dados contribuem para a hipótese de redução do número diploide nas espécies que apresentam polimorfismos cromossômicos e cromossomos sexuais, além de contribuir para inferências sobre os mecanismos de evolução cariotípica que favoreceu a diversificação do gênero Ancistrus, o mais representativo na tribo Ancistrini.

Hidden Diversity in the Populations of the Armored Catfish Ancistrus Kner, 1854 (Loricariidae, Hypostominae) from the Paraná River Basin Revealed by Molecular and Cytogenetic Data

“…In the present study, in fact, the inclusion of a cytogenetic approach was crucial to the recognition of the “candidate species,” given that the distinct chromosomal formulae found in the four lineages (clades I, II, IV, and V) emphasizes their reciprocal monophyly and the lack of gene flow between them. The results obtained also complement the available cytogenetic data to the Ancistrus species, since these studies are currently restricted to the taxa found in the Paraguay (Mato Grosso) and Amazon (Manaus) basins (de Oliveira et al, 2007 , 2008 , 2009 ; Mariotto et al, 2011 , 2013 ; Favarato et al, 2016 ; Prizon et al, 2016 ).…”

“…With 69 species, Ancistrus Kner, 1854 is one of the most diverse Ancistrini groups, the second richest in species of the Loricariidae (Ferraris, 2007 ; Bifi et al, 2009 ; Froese and Pauly, 2017 ). Cytogenetic data on Ancistrus are still scarce, and restricted to species found in the basins of the Paraguay River in Mato Grosso, and the Amazon, in Manaus (de Oliveira et al, 2009 ; Mariotto et al, 2011 , 2013 ; Favarato et al, 2016 ; Prizon et al, 2016 ). While the cytogenetics of Ancistrus species from other river basins are still unknown, considerable variability has been found in this genus, with diploid (2n) numbers of 34, 38, 40, 42, 44, 48, 50, and 54 chromosomes.…”

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

“…The karyotypes described for the genus Ancistrus have been obtained from species found in the basins of the Paraguay and Amazon Rivers, with extensive variability observed in the genus, whose diploid numbers vary of 34, 38, 40, 42, 44, 46, 48, 50, 52 and 54 chromosomes (de Oliveira et al 2009, Mariotto et al 2011, 2013, Favarato et al 2016). The available descriptions of karyotypes for unidentified Ancistrus species emphasize the potential diversity of the genus in these basins.…”

“…01, Ancistrus sp. 03 (Mariotto et al 2013) and Ancistrus claro (Mariotto et al 2011) species, with karyotype formula of 14m+8sm+8st+24a. These species have a proportion karyotype of 22 meta-submetacentric (40.7%) and 32 st-acrocentric chromosomes (59.3%).…”

“…de Oliveira et al 2009, Mariotto et al 2011, 2013, Favarato et al 2016). The karyotype data available for this genus indicate considerable chromosomal diversity, with diploid numbers ranging from 2n=34 chromosomes in Ancistrus cuiabae (Mariotto et al 2009) to 2n=54 in Ancistrus claro (Mariotto et al 2011).…”