Trends on the Karyotype Acrocentrization Within Carangidae (Perciformes): A New Phylogenetic Evidence About a Traditional Marine Paradigm.

Abstract

Carangidae is a morphologically diverse family of marine fish, characterized by stable karyotypes, predominantly with 2n = 48, composed of acrocentric chromosomes (A). This stability is shared with other families of the order Perciformes, which resulted in the hypothesis that 48A is a plesiomorphic karyotype of the group. We tested this hypothesis in the Carangidae family using comparative phylogenetic methods, investigating the evolution of karyotype characters (including chromosome number, morphology, and number of chromosome arms per karyotype [fundamental number, FN]). Our analyses revealed that 2n = 48 is most likely the ancestral chromosome number for the family. However, an extremely variable number of FNs, always above 48, was observed in basal clades within the family and sister groups. On the other hand, the reduced FN = 48 was consistently observed only in the most derived clades, indicating a tendency for acrocentrization. The number of acrocentric chromosomes apparently was accompanied by a trend of reduction in the genome size (1C-value), suggesting that these changes might be correlated. Our data contradict the marine fish hypothesis that the 2n = 48 acrocentric karyotype is plesiomorphic, at least for Carangidae, and reveal the importance for the correct interpretation of karyotype in a temporal and phylogenetic context.