Sex Chromosomes and Internal Telomeric Sequences in Dormitator latifrons (Richardson 1844) (Eleotridae: Eleotrinae): An Insight into Their Origin in the Genus

Abstract

The freshwater fish species Dormitator latifrons, commonly named the Pacific fat sleeper, is an important food resource in CentralSouth America, yet almost no genetic information on it is available. A cytogenetic analysis of this species was undertaken by standard and molecular techniques (chromosomal mapping of 18S rDNA, 5S rDNA, and telomeric repeats), aiming to describe the karyotype features, verify the presence of sex chromosomes described in congeneric species, and make inferences on chromosome evolution in the genus. The karyotype (2n = 46) is mainly composed of metacentric and submetacentic chromosomes, with nucleolar organizer regions (NORs) localized on the short arms of submetacentric pair 10. The presence of XX/XY sex chromosomes was observed, with the X chromosome carrying the 5S rDNA sequences. These heterochromosomes likely appeared before 1 million years ago, since they are shared with another derived Dormitator species (Dormitator maculatus) distributed in the Western Atlantic. Telomeric repeats hybridize to the terminal portions of almost all chromosomes; additional interstitial sites are present in the centromeric region, suggesting pericentromeric inversions as the main rearrangement mechanisms that has driven karyotypic evolution in the genus. The data provided here contribute to improving the cytogenetics knowledge of D. latifrons, offering basic information that could be useful in aquaculture farming of this neotropical fish.

Biology and use of the Pacific fat sleeper Dormitator latifrons (Richardson, 1844): state of the art review

“…Recent genetic research found the same sex chromosomes and other origin similarities between D. latifrons and the western Atlantic D. maculatus. The internal telomeric sequence suggests the heterochromosomes of the genus appear before one million years ago; the study also concludes that more research on chromosome localization of telomeric repeated sequences in other Dormitator and other Eleotrinae species is necessary to get a more comprehensive picture of the role of such sequences in the karyotype evolution of this group (Gomes-Paim et al 2020). Furthermore, Galván-Quesada et al (2016) demonstrated, through phylo-genetic analysis, that D. latifrons are the only species of the genus found in the Pacific Ocean.…”

“…Dormitator latifrons (Richardson, 1844), also called fat sleeper, chame, puyeque, popoyote, chococo, or chalaco, is a fish that has attracted biological interest for more than a hundred years (Castro-Rivera et al 2005, Basto-Rosales et al 2019). The first recorded study is by Eigenman & Fordice (1885); however, since then, the amount of published information has been scarce, most of it about specific aspects of the ecology, physiology, and parasitology of the species (Todd 1973, 1975, Yáñez-Arancibia & Díaz-González 1977, Chang & Navas 1984, Lu et al 1998, Garrido-Olvera et al 2004, Violante-González et al 2008a,b, McDowall 2009.…”

Fish Cytogenetics: Present and Future

“…As an example, one paper focused on the freshwater fish Dormitator latifrons that represents an important food resource in Central South America and whose karyotype was still undescribed. In this species, the presence of an XY chromosome system and mapping of repeated sequences repeats allowed the identification of the main mechanisms of chromosome rearrangement that have driven karyotypic evolution in the genus [ 19 ]. Other papers reported polymorphism related to the presence of B chromosomes [ 20 , 21 ].…”