Abstract
Surgeonfishes are a species-rich group and a major biomass on coral reefs. Three species are commonly found throughout South Atlantic, Acanthurus bahianus, A. chirurgus, and A. coeruleus. In this paper, we present the first cytogenetic data of these species, revealing a sequential chromosomal diversification. A. coeruleus was characterized by a relatively conserved karyotype evolved by pericentric inversions of some pairs (2n = 48, 2sm + 4st + 42a). In contrast, the karyotypes of A. bahianus (2n = 36) and A. chirurgus (2n = 34) were highly differentiated by the presence of six large metacentric pairs in A. bahianus (12m + 2sm + 4st + 18a) and A. chirurgus (12m + 2sm + 4st +1 6a) probably derived by chromosomal fusions that corroborate their closer relationship. A discernible in tandem fusion represents an autapomorphic character to A. chirurgus. In spite of macrostructure variation, single nucleolar organizer regions (NORs) on short arms of a subtelocentric pair and similar distribution of C-bands were observed in the three species. Overlapping of chromosomal data with molecular phylogeny indicated pericentric inversions which took place nearly at 19 Ma while centric fusions are as recent as 5 Ma. A physical mapping of coding and noncoding sequences in Acanthurus could clarify the role of additional rearrangements during their chromosomal evolution.
Highlights
Acanthuridae are a monophyletic fish family composed of about 80 species, popularly known as surgeonfishes or tangs [1]
In A. bahianus, terminal C-bands were observed in some pairs (Figure 2(d))
The low genetic structure in reef fish species has been correlated to the production of planktonic eggs and/or larvae that can be dispersed over large distances [12]
Summary
Acanthuridae are a monophyletic fish family composed of about 80 species, popularly known as surgeonfishes or tangs [1]. This is an ancient group (nearly 54 Ma) and most of genera (Acanthurus, Naso, Paracanthurus, Zebrasoma, and Ctenochaetus) diverged between 17 and 21 Ma in Early Miocene [2]. The genus Acanthurus is the largest within the family, but monophyly of the genus is still controversial [2,3,4,5] This fish group is morphologically and ecologically diversified, mainly in relation to foraging behavior and dentition, composing one of the most representative herbivorous fish group on coral reefs [2, 6]
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