Evolutionary cytogenetics of the Hoplias lacerdae, Miranda Ribeiro, 1908 group: a particular pathway concerning the other Erythrinidae fish

Abstract

The taxonomy/systematics of the Erythrinidae fish is still imprecise, with several doubts on their relationships. Karyotypes and chromosomal characteristics of some species of the Hoplias lacerdae group (Erythrinidae), from different Brazilian hydrographic basins and pisciculture stations, were analyzed in the present study, using conventional Giemsa staining, C-banding, silver staining, Mithramycin and Distamycin/DAPI fluorochromes, and fluorescent in situ hybridization (FISH). A diploid chromosome number of 2n = 50 and karyotypes composed of meta-and submetacentric chromosomes without sex-related differences were found. Only one active NOR (Nucleolar Organizer Region) site was found, which was identified by silver staining (Ag-NOR) and FISH, located on the chromosome pair 11, although additional 45S rDNA sites were also mapped on other chromosome pairs only by FISH. The Ag-NOR of the chromosome pair 11 was found to be GC-rich, appearing positive after Mithramycin staining. Mithramycin-positive/ DAPI-negative sites were also observed in the centromeric/pericentomeric regions of the chromosome pairs 4, 6, 15, and 19, which have also affinity to silver nitrate. However, these four sites were not detected by FISH with the rDNA probe, indicating to be only argentophilic GC-rich heterochromatic regions. Chromosome data show that the karyotype evolution in Hoplias lacerdae group is relatively conserved and follows a particular pathway concerning the other Erythrinidae fishes, such as Hoplias malabaricus, Hoplerythrinus unitaeniatus, and Erythrinus erythrinus, in which polytypic karyotypes are found. Thus, the H. lacerdae group shows chromosome features that are not closely related to those of the congeneric H. malabaricus group. These finds, together with genetic and morphologic data, are important tools to be considered in a major revision of the Erythrinidae family, as well as for conservation programs.Keywords: erythrinid, chromosome features, karyotypic evolution, cytotaxonomy. Citogenética evolutiva do grupo Hoplias lacerdae. Um comportamento particular em relação aos outros peixes eritrinídeos ResumoA taxonomia dos Erythrinidae encontra-se ainda por ser totalmente esclarecida, existindo várias dúvidas sobre suas relações filogenéticas. No presente estudo, foram analisados os cariótipos e características cromossômicas de algumas espécies do grupo Hoplias lacerdae (Erythrinidae), de diferentes bacias hidrográficas do Brasil e estações de piscicultura, empregando-se a coloração Giemsa convencional, bandamento C, coloração com nitrato de prata, fluorocromos Mitramicina e Distamicina/DAPI, e hibridação fluorescente in situ (FISH). O número diplóide de 2n = 50 cromossomos foi constante, sendo os cariótipos formados por cromossomos de dois braços, meta-e submetacêntricos, sem diferenciação relacionada ao sexo. Foi identificado apenas um sítio ativo de região organizadora de nucléolo (NOR), presente no par cromossômico no. 11, identificado tanto pela coloração com nitrato de prata (Ag-NOR) como por FISH com son...

Comparative Cytogenetics of Giant Trahiras <i>Hoplias aimara </i>and <i>H. intermedius </i>(Characiformes, Erythrinidae): Chromosomal Characteristics of Minor and Major Ribosomal DNA and Cross-Species Repetitive Centromeric Sequences Mapping Differ among Morphologically Identical Karyotypes

“…aimara . Characteristically, all these more evident C-positive sites were revealed to be GC-rich, corroborating some previous data [Morelli et al, 2007]. Thus, 2 distinct types of heterochromatin were present in H. intermedius : a GC-rich one, exclusive of the conspicuous heterochromatic sites, and another non-GC-rich, found at the centromere region in the majority of the chromosomes.…”

“…Our data corroborate the relative conservation of the karyotyes in the species of the H. lacerdae group [Morelli et al, 2007], which is in contrast to that of other genera and species of Erythrinidae, where, as a rule, great karyotype diversity was observed. This is well exemplified in H. malabaricus [Bertollo et al, 2000], Hoplerythrinus unitaeniatus [Giuliano-Caetano and Bertollo, 1988;Diniz and Bertollo, 2003] and in Erythrinus erythrinus [Bertollo et al, 2004].…”

“…aimara, exhibit conservation in their karyotypes, as already documented for other Erythrinidae species/populations of the H . lacerdae group [Morelli et al, 2007]. However, some specific differences in some m and sm chromosomes between the species were observed.…”

“…In this group, chromosome data are only available for specimens from a few Brazilian populations. These populations showed similar karyotypes with 2n = 50 meta-and submetacentric chromosomes [Bertollo et al, 1978;Morelli et al, 2007].…”

Chromosomes as Tools for Discovering Biodiversity – The Case of Erythrinidae Fish Family

“…The H. lacerdae group includes six recently recognized species: H. brasiliensis, H. aimara, (Oyakawa & Mattox, 2009). This group of species has a conserved karyotype with an invariable diploid chromosome number (2n = 50) and a karyotype with m and sm chromosomes but no morphologically differentiated sex chromosomes (Bertollo et al, 1978;Morelli et al, 2007;Blanco et al, 2011). Therefore, it seems that speciation in the lacerdae group was not accompanied by observable changes at the chromosome level.…”