Karyotypic characterization of Prochilodus mariae, Semaprochilodus kneri and S. laticeps(Teleostei: Prochilodontidae) from Caicara del Orinoco, Venezuela

Abstract

Fish of the family Prochilodontidae are considered one of the most important components of commercial and subsistence fishery in freshwater environments in South America. This family consists of 21 species and three genera. In the present study, the karyotypes of Prochilodus mariae, Semaprochilodus kneri, and S. laticeps from Caicara del Orinoco, Bolivar State, Venezuela were studied. The species P. mariae, S. kneri and S. laticeps exhibited 2n=54 chromosomes (40 metacentric and 14 submetacentric), a single chromosome pair with nucleolus organizer regions, and a large amount of heterochromatin found at centromeric and pericentromeric positions in almost all chromosomes. The P. mariae specimens studied displayed 0 to 3 supernumerary microchromosomes. The data obtained here confirm the conservative nature of the chromosome number and morphology of Prochilodontidae and reinforce the hypothesis that small structural chromosome rearrangements were the main cause of the karyotypic diversification seen in this group.Os peixes da família Prochilodontidae são considerados um dos componentes mais importantes da pesca comercial e de subsistência em ambientes de água doce na América do Sul. Essa família compreende 21 espécies e três gêneros. No presente estudo foram analisados os cariótipos de Prochilodus mariae, Semaprochilodus kneri e S. laticeps provenientes de Caicara del Orinoco, Estado Bolivar, Venezuela. As espécies P. mariae, S. kneri e S. laticeps apresentaram 2n=54 cromossomos (40 metacêntricos e 14 submetacêntricos), um único par de cromossomos com regiões organizadoras de nucléolo e uma grande quantidade de heterocromatina em posição centromérica e pericentromérica de quase todos os cromossomos. Os espécimes estudados de P. mariae apresentaram de 0 a 3 microcromossomos supranumerários. Os dados obtidos aqui confirmam a natureza conservada do número e da morfologia cromossômica dos Prochilodontidae e reforçam a hipótese de que pequenos rearranjos estruturais foram os principais eventos fixados na diversificação cariotípica do grupo.

Karyological characterization of <i>Mugil trichodon</i> Poey, 1876 (Pisces: Mugilidae)

“…This correlation between the secondary constrictions in metaphase plates stained with Giemsa and NORs, demonstrated by silver nitrate, occurs in many other fish species (Rodriguez-Daga et al, 1993;Oliveira et al, 2003), but to the best of our knowledge this is the first report of interstitial localization of NORs in Mugilidae. It is most likely an exclusive apomorphy in the species M. trichodon, probably caused by a paracentric inversion involving NOR sites.…”

Transmission rate variation among three B chromosome variants in the fish Prochilodus lineatus (Characiformes, Prochilodontidae)

“…However, Voltolin et al (2011) recently detected the presence of eight and nine supernumerary chromosomes in individuals of this species resulting from induced crossings. Supernumerary chromosomes exhibit a remarkable variation in size and morphology among fish, i.e., the occurrence of large genomic elements as macrochromosomes was described in species of the genus Astyanax (Maistro et al 1992, Salvador and Moreira-Filho 1992, Vicente et al 1996, Moreira-Filho et al 2001, Ferro et al 2003, Hashimoto et al 2008; of medium size in Rhamdia Bertollo 1990, Fenocchio et al 2000); and also as small elements identified as microchromosomes in Prochilodus (Pauls and Bertollo 1983, Venere et al 1999, Cavallaro et al 2000, Oliveira et al 2003, Voltolin et al 2009). Artoni et al (2006), studying specimens of P. lineatus from the Mogi-Guaçu River, observed the presence of three types of supernumerary microchromosomes in this species, which were classified as B-acrocentric, B-metacentric, and B-submetacentric.…”

Stable karyotypes: a general rule for the fish of the family Prochilodontidae?

“…Cytogenetically, the genera Prochilodus and Semaprochilodus have a relatively stable karyotypic macrostructures, with 2n = 54 chromosomes of the metaand submetacentric types, one pair bearing Ag-NORs sites, and a principally pericentromeric distribution of their heterochromatin (Pauls & Bertollo, 1990;Oliveira et al, 2003;Hatanaka & Galetti, 2004). However, some chromosomal markers are not shared by all of the representatives of the family studied to date, such as the presence of supernumerary chromosomes in populations of P. lineatus Artoni et al, 2006;Vicari et al, 2006) and P. nigricans (Venere et al, 1999), the system of the sex chromosomes ZZ/ZW in S. taeniurus (Feldberg et al, 1987), and the syntenic locations of the 18S and 5S rDNAs Hatanaka & Galetti, 2004;Vicari et al, 2006).…”

“…In relation to cytogenetics, the chromosome number and morphologies of the species of the genus Semaprochilodus studied to date indicate the conserved nature of 2n = 54 chromosomes of the metaand submetacentric type characteristic of the Prochilodontidae (Pauls & Bertollo, 1990;Oliveira et al, 2003). The character encountered with the greatest divergence until now in terms of the karyotypic macrostructure of the species of this genus is the presence of a ZZ/ZW sex chromosome system in S. taeniurus (Feldberg et al, 1987).…”

“…As these fish are quite important to commercial fishing enterprises (Barletta et al, 2010), a number of studies examining their morphology (Ribeiro, 1983(Ribeiro, , 1985, reproduction (Vazzoler et al, 1989), biology (Leite & Araújo-Lima, 2002;Oliveira, 2003;Lima & Araújo-Lima, 2004;Leite et al, 2006), physiology (Val et al, 1984(Val et al, , 1998, and genetics (Feldberg et al, 1987;Teixeira et al, 1990;Oliveira et al, 2003) have already been undertaken.…”