Chromosomal similarity between two species ofApteronotus albifronscomplex (Apteronotidae–Gymnotiformes) implications in cytotaxonomy and karyotypic evolution

Extensive Karyotype Reorganization in the Fish Gymnotus arapaima (Gymnotiformes, Gymnotidae) Highlighted by Zoo-FISH Analysis

“…Cytogenetics has been an important tool in cytotaxonomy and has proved to be very useful in understanding the evolutionary processes behind the diversification of Gymnotus . The Gymnotiformes order has considerable variation, not only in diploid number (from 2 n = 24 in Apteronotus albifrons , Howell, 1972 ; Almeida-Toledo et al, 1981 ; Mendes et al, 2012 ; to 2 n = 74 in Rhabdolichops cf eastward , Suárez et al, 2017 ) but also in the karyotype formula and location of repetitive sequences (Fernandes et al, 2005 ; Almeida-Toledo et al, 2007 ; Silva et al, 2009 ; da Silva et al, 2013 ; Jesus et al, 2016 ; Araya-Jaime et al, 2017 ; Batista et al, 2017 ; Sousa et al, 2017 ; Takagui et al, 2017 ). Recently, fluorescence in situ hybridization (FISH), has played an important role in understanding the genome structure of fish species (Yi et al, 2003 ; Cabral-de-Mello and Martins, 2010 ; Martins et al, 2011 ; Vicari et al, 2011 ; Gornung, 2013 ; Knytl et al, 2013 ; Yano et al, 2017 ) and molecular cytogenetic studies in Gymnotiformes have shown dynamic reorganization, including pericentric inversions observed through repetitive DNA position (Fernandes et al, 2017 ), sequence dispersion via transposable elements and the association between different repetitive sequences (Utsunomia et al, 2014 ; da Silva et al, 2016 ; Machado et al, 2017 ) and the presence of different sex chromosome systems (Margarido et al, 2007 ; Henning et al, 2008 , 2011 ; da Silva et al, 2011 , 2014 ; Almeida et al, 2015 ).…”

Archolaemus janeae (Gymnotiformes, Teleostei): First insights into karyotype and repetitive DNA distribution in two populations of the Amazon

“…The cytogenetic studies published for Gymnotiformes have given insight into the diversity and karyotype evolution of this order (Cardoso et al., 2015 ; Fernandes, Baumgärtner, et al., 2017 ; Fernandes, Paiz, et al., 2017 ; Faria‐Pereira et al, 2019 ; Milhomem et al., 2012 ; Sene et al., 2014 ; Silva et al., 2008 ; da Silva et al., 2016 ; da Silva et al, 2014 ). The diploid chromosome number (2 n ) ranges from 2 n = 24 in Apteronotus albifrons (Linnaeus, 1766) (Apteronotidae; Fernandes, Paiz, et al., 2017 ; Takagui et al., 2017 ) to 2 n = 74 in Rhabdolichops cf eastwardi Lundberg, Mago‐Leccia, 1986 (Sternopygidae; Suárez et al., 2017 ). Chromosomal studies have shown that species diversity may be higher than previously considered, for there are morphologically similar species (cryptic species) with different karyotypes, such as in Gymnotus carapo Linnaeus, 1758 (Milhomem et al., 2008 ; Nagamachi et al., 2010 ).…”