Atlantic moonfishes: independent pathways of karyotypic and morphological differentiation

Abstract

Fish of the genus Selene, known as lookdowns or moonfish, are one of the most morphologically derived groups of the family Carangidae, whose phylogenetic relationships are still largely unknown. In this study, we discuss karyoevolutionary aspects of three representatives of this genus from the Western Atlantic: Selene brownii (2n = 48; FN = 48), Selene setapinnis (2n = 46; FN = 48), and Selene vomer (2n = 48; FN = 50). Their body patterns were also investigated and compared to one another and in relation to two other species of different genera. Two mechanisms of karyotypic evolution seem to have acted in the diversification of this genus, namely pericentric inversions and centric fusions. Mapping of rDNA sequences showed that chromosome pairs bearing 5S rDNA sites are similar, whereas those bearing 18 rDNA sites are morphologically distinct while apparently also exhibiting interspecies synteny. Although the nucleolar organizer-bearing chromosomes are extremely efficient cytotaxonomic markers among Selene species, others cytogenetic patterns of these species are relatively conserved. Hybridization with telomeric probes (TTAGGG) n did not exhibit interstitial telomeric sites (ITS), especially in S. setapinnis, where, along with a reduction in diploid number, a large metacentric pair derived from centric fusion is present. Data obtained by geometric morphometrics enable a clear morphological distinction among the three species, as well as in relation to two other species of the genus Caranx and Oligoplites. Data obtained suggest that morphologic evolution in Selene species was primarily dissociated from visible changes that occurred at the chromosomal level.

Co-located 18S/5S rDNA arrays: an ancient and unusual chromosomal trait in Julidini species (Labridae, Perciformes)

“…Among the repetitive DNAs, rDNA has a major role in karyotype diversification. In fact, species from various fish families exhibit 18S and 5S rDNAs sequences involved in chromosome fusion points (Molina and Galetti 2002, Ziemniczak 2011, Jacobina et al 2013, Getlekha et al 2016), indicating their probable involvement in the chromosomal reorganization. In this sense, the presence of an 18S rDNA site in the interstitial position on pair 5 in Halichoeres radiatus , in contrast to its terminal position in the homeologous chromosomes of the remaining species, puts in evidence a cryptic paracentric inversion in that chromosome pair.…”

Physical mapping of 18S and 5S genes in pelagic species of the genera Caranx and Carangoides (Carangidae)

“…In some genera, such as Trachinotus (NF = 52-58) and Trachurus (NF = 50-66), pericentric inversions have played an important role in the karyotype diversification (Murofushi and Yoshida, 1979;Caputo et al, 1996;Rodrigues et al, 2007, Jacobina et al, 2012aAccioly et al, 2012). Moreover, other sporadic mechanisms may have contributed to the chromosomal evolution of this group, particularly Robertsonian translocations, which are found in Trachurus, Seriola, and Selene (Vitturi et al, 1986;Jacobina et al, 2012b).…”

Evolutionary dynamics of rDNA genes on chromosomes of the Eucinostomus fishes: cytotaxonomic and karyoevolutive implications

“…Thus, they may evolve independently and are subject to individual selective pressure (Amarasinghe and Carlson, 1998). Occasionally, in Perciformes, both the 5S and 18S rDNA sites may be diversified (Motta-Neto et al, 2012), standing out not only as efficient species markers but also as population markers , and may be involved in chromosome rearrangements (Jacobina et al, 2013).…”