Cytogenetic analysis in western Atlantic snappers (Perciformes, Lutjanidae)

Abstract

The Lutjanidae or snappers are a family of perciform fishes, mainly marine but with some members living in estuaries and entering fresh water to feed. Some are important food fish. Cytogenetic data for Lutjanidae are scarce. In the present work, we cytogenetically characterized through conventional Giemsa staining techniques, Ag-NOR and C-banding the species Ocyurus chrysurus, Lutjanus analis, L. alexandrei, L. cyanopterus, L. jocu and L. synagris, all found along the Brazilian coast. Karyotype analysis of all six species showed a modal value of 2n = 48 acrocentric chromosomes. Single NORs were found at pericentromeric position on the long arms of the 2 nd pair in O. chrysurus, L. alexandrei and L. cyanopterus, on the 5 th pair in L. analis and on the 23 rd pair in L. synagris. The species L. jocu presented multiple NORs located on the 2 nd pair at a pericentromeric region and on the 5 th pair at a telomeric region. Heterochromatic blocks were identified at the centromeric region of all chromosomes of the studied species. These results indicate that, despite of the chromosomal stability of this family, a relative structural diversification seems to have occurred in the chromosome evolution of the group. Such diversification was evidenced by divergent number and location of ribosomal sites among species. The NOR-bearing pairs represented an efficient cytotaxonomic marker for most of the analyzed species. The data suggest that the presence of interstitially located single NORs on a large acrocentric pair should represent a basal condition for lutjanids.

Cytogenetic characterization of Rhomboplites aurorubens and Ocyurus chrysurus, two monotypic genera of Lutjaninae from Cubagua Island, Venezuela, with a review of the cytogenetics of Lutjanidae (Teleostei: Perciformes)

“…The 48 all-acrocentrics karyotype here reported for the examined specimens of O. chrysurus is consistent with data reported by Rocha & Molina (2008) for specimens from the Brazilian north-eastern coast. This karyotype is shared by 10 out of the 13 species so far analyzed ( Table 1).…”

“…Thus, in the former species, the Robertsonian rearrangement is related to the presence of a chromosomal sex determination mechanism, while in the latter it is apparently unrelated to sex and reflects an intra-specific chromosome polymorphism. It is worth noting that specimens of L. synagris from Brazil (Rocha & Molina, 2008) do not show any biarmed chromosome. The pattern of the heterochromatin distribution observed in O. chrysurus and R. aurorubens confirms that a limited presence of heterochromatic blocks at the centromeres of all chromosomes is a general characteristic of Lutjanidae, as this pattern is shared by all the 11 species investigated in this sense (Table 1), including those species for which more than one population has been studied, such as L. analis, L. synagris (Nirchio et al, 2008;Rocha & Molina, 2008) and O. chrysurus (Rocha & Molina, 2008;this paper).…”

“…However, in 2008, three different studies added new data, mainly for species of the genus Lutjanus (Nirchio et al, 2008;Rocha & Molina, 2008;Ueno & Takai, 2008), reporting karyotypes as well as several finer cytogenetic features. All these studies have shown that a general chromosome homogeneity occurs within the family, but that derived karyotypes can also be found, whose phylogenetic interpretation remains unclear.…”

Preferential accumulation of sex and Bs chromosomes in biarmed karyotypes by meiotic drive and rates of chromosomal changes in fishes

“…This family is distributed in wide marine regions, with many estuarine and rare freshwater species forming large populations (Nelson 2006). In addition to vicariant events, the ecological mechanisms of speciation that contributed to species richness in this family (Rocha and Molina 2008), combined with special stable features of its karyotype (Nirchio et al 2007) could be the major causes of karyotype stasis. However, conservative karyotypes seem to be involved in the reduction of post-zygotic reproductive isolation (Molina et al 2013) by the occurrence of natural and induced hybrids in the Centrarchidae and Carangidae families (Koppelman 1994, Murakami et al 2007.…”

Population Structure of Lutjanus purpureus (Lutjanidae - Perciformes) on the Brazilian coast: further existence evidence of a single species of red snapper in the western Atlantic

“…Hybridization was recorded in a number of lutjanid species, such as L. synagris and O. chrysurus (Domeier andClarke 1992, Loftus 1992). Recent analyses (Rocha and Molina 2008, Nirchio et al 2008, 2009) have confirmed that the chromosomic constitution of the lutjanids, including species of the genera Lutjanus, Ocyurus, and Rhomboplites, is highly conserved, which would permit introgressive hybridization or hybridization. At the moment, however, there is no evidence of such hybridization in the red snappers.…”