Karyotype Patterns ofHypsolebias antenori(Cyprinodontiformes: Rivulidae): An Endangered Killifish of the Semiarid Region of Brazil

Abstract

Annual fish which belong to the order Cyprinodontiformes constitute an excellent model for evolutionary studies. their short life cycle, distribution in ecologically dynamic environments, and low agility make them favorable for genetic analyses. The species Hypsolebias antenori (Rivulidae), encountered in seasonal pools located in the semiarid region of Northeastern Brazil, has been the object of surveys with a view to study its ecological and behavioral aspects. This study reports on the karyotype patterns of this species, which represents the first contribution to the cytogenetics of this genus. The karyotype of this species is composed of 2n = 48 chromosomes (6m + 4sm + 36st; NF = 96); the heterochromatic regions are located in centromeric or pericentromeric position and are more pronounced in the nucleolar organizer regions. Two sites Ag-NORs/CMA+/DAPI were identified in the short arms of pairs 2 (metacentric) and 21 (subtelocentric). Unlike the other species of this family which show an evolution modulated by events of centric fusions, H. antenori shows the maintenance of a basal diploid number and the large number of bibrachial elements indicates karyotypic diversification derived by pericentric inversions. Cytogenetic analyzes in this species will provide new taxonomic markers capable of being utilized in conservation issues and systematics.

Chromosomal organization of four classes of repetitive DNA sequences in killifish Orestias ascotanensis Parenti, 1984 (Cyprinodontiformes, Cyprinodontidae)

“…The organization of the repetitive fraction of the genome in Cyprinodontiformes fish has remained relatively unexplored, with prior studies focusing primarily on the distribution and composition of constitutive heterochromatin and physical mapping of 18S rDNA genes. Noteworthy studies include reports on: Fundulus (Lacépède, 1803) ( Kornfield 1981 ); Austrolebias Costa, 1998 ( García et al 1993 , 1995 , 2001 , 2014 , 2015 ); Aphanius Nardo, 1827 ( Vitturi et al 2005 , Gaffaroglu et al 2014 ) and Hypsolebias Costa, 2006 ( Do Nascimento et al 2014 ), with constitutive heterochromatin found to be distributed mainly in centromeric, telomeric and interstitial regions. In addition, in some species of Chromaphyosemion Myers, 1924, conspicuous blocks of HC have been identified in the short arm of bi-armed chromosomes ( Völker et al 2005 , Völker et al 2006 , Volker et al 2007, Völker et al 2008 ).…”

Reproductive strategies and chromosomal aberrations affect survival in the Rivuliid fish Hypsolebias sertanejo

“…In this context, much research effort has been made to preserve rivulids, as knowledge in the fields of biology and ecology is necessary to establish protocols for species conservation and environmental reconstitution action (Volcan et al, 2010(Volcan et al, , 2011. In this sense, studies on genetic characterization (Nascimento et al, 2014;Kim et al, 2016), ecology (Abilhoa et al, 2010;Keppeler et al, 2013), taxonomy (Costa et al, 2012, Costa andAmorim, 2014) and reproduction (García et al, 2008;Cassel et al, 2013;Passos et al, 2014;Schalk et al, 2014) have already been performed for some Rivulidae species. They present a huge diversity of reproductive strategies that include external (Jara et al, 1995;Volcan et al, 2011) and internal fertilization (Costa et al, 2016), in addition to the self-fertilization (Avise and Tatarenkov, 2015), a uniquely reported case among vertebrates.…”