Multiple pericentric inversions and chromosomal divergence in the reef fishes Stegastes (Perciformes, Pomacentridae)

Abstract

Damselfishes (Pomacentridae, Perciformes) occur in all major oceans of the world and, with approximately 320 species, represent one of the most diverse families of marine Teleostei. The taxonomy of these reef fishes is problematic because of the large number of complex species and the range of color patterns they display, which vary among individuals and populations of the same species. In this study, we examined the cytogenetic composition of four species of Stegastes (S. pictus, S. fuscus, S. variabilis and S. leucostictus) found along the coast of Brazil. Stegastes pictus had a chromosomal number of 2n = 48 (14m+28sm+2st+4a, fundamental number (FN) = 92), S. fuscus had 2n = 48 (20m+22sm+6a, FN = 90), S. variabilis had 2n = 48 (18m+22sm+8a, FN = 88), and S. leucostictus had 2n = 48, (18m+22sm+8a, FN = 88). The nucleolar organizing regions were single and homologous in all of the species, and were located in the interstitial region on the short arm of the first submetacentric pair. The heterochromatin segments were reduced in size and were distributed conservatively over the centromeric and pericentromeric regions of most of the chromosomes. The marked divergence in the number of chromosomal arms, compared to other Perciformes (2n = 48, FN = 48), indicated that varying degrees of multiple pericentric inversions had occurred during the karyotypic evolution of the Pomacentridae. Subtle karyotypic differences between S. variabilis and S. leucostictus suggested a recent divergence or that their karyotypes were less susceptible to changes. These results indicate that cytogenetic analyses could provide important complementary data for the characterization of populations and species of Stegastes and damselfishes in general.

Cytogenetic studies in Brazilian marine Sciaenidae and Sparidae fishes (Perciformes)

“…The combined action of these features would restrain the fixation of polymorphic chromosomal rearrangements and lead to a reduced karyotypic diversification. This hypothesis is corroborated by the identification of some marine species bearing derived karyotypes that lack one or more of such features (Molina and Galetti Jr., 2004).…”

“…Several reports have demonstrated that the degree of karyotypic differentiation (number of changes in FN values) in some families of marine reef Perciformes (i.e., Pomacentridae; Labridae) is inversely related to the dispersive potential provided by the extent of pelagic larval duration of each species (Molina and Galetti Jr., 2004;Molina, 2006;Sena and Molina, 2007).…”

Chromosomal distribution of two multigene families and the unusual occurrence of an X1X1X2X2/X1X2Y sex chromosome system in the dolphinfish (Coryphaenidae): An evolutionary perspective

“…Some families of reef fish display marked karyotypic derivation, such as Pomacentridae and Gobiidae, among others (Ene, 2003;Molina and Galetti, 2004b). In contrast, little is known about the karyotypic patterns of large neritic pelagic fish, which include migratory adults that are able to undertake long journeys to reproductive sites.…”

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

“…Allopatric isolation seems to act in accordance with the peculiar biological patterns of distinct fish groups in the fixation of chromosomal rearrangements (Molina and Galetti 2004). About 43% (11,952) of fish species exclusively inhabit freshwater rivers and lakes, which cover only 1% of the Earth's surface.…”