Phylogeny of the Serrasalmidae (Characiformes) based on mitochondrial DNA sequences

Abstract

Previous studies based on DNA sequences of mitochondrial (mt) rRNA genes showed three main groups within the subfamily Serrasalminae: (1) a "pacu" clade of herbivores (Colossoma, Mylossoma, Piaractus); (2) the "Myleus" clade (Myleus, Mylesinus, Tometes, Ossubtus); and (3) the "piranha" clade (Serrasalmus, Pygocentrus, Pygopristis, Pristobrycon, Catoprion, Metynnis). The genus Acnodon was placed as the sister taxon of clade (2+3). However, poor resolution within each clade was obtained due to low levels of variation among rRNA gene sequences. Complete sequences of the hypervariable mtDNA control region for a total of 45 taxa, and additional sequences of 12S and 16S rRNA from a total of 74 taxa representing all genera in the family are now presented to address intragroup relationships. Control region sequences of several serrasalmid species exhibit tandem repeats of short motifs (12 to 33 bp) in the 3' end of this region, accounting for substantial length variation. Bayesian inference and maximum parsimony analyses of these sequences identify the same groupings as before and provide further evidence to support the following observations: (a) Serrasalmus gouldingi and species of Pristobrycon (non-striolatus) form a monophyletic group that is the sister group to other species of Serrasalmus and Pygocentrus; (b) Catoprion, Pygopristis, and Pristobrycon striolatus form a well supported clade, sister to the group described above; (c) some taxa assigned to the genus Myloplus (M. asterias, M tiete, M ternetzi, and M rubripinnis) form a well supported group whereas other Myloplus species remain with uncertain affinities (d) Mylesinus, Tometes and Myleus setiger form a monophyletic group.

Spermiogenesis and spermatozoa ultrastructure in the Serrasalminae (Ostariophysi: Characiformes) with further evidence on the relationships of the piranhas and pacus

“…The main differences of the spermatic cells among these three genera are the largest floccus of chromatin, the deepest nuclear fossa of Salminus and Brycon, and the shortest cytoplasmic sleeve, and the flagellar fins of Piaractus. Piaractus occupies a basal position of in Serrasalminae along with Mylossoma and Colossoma (Ortí et al, 1996(Ortí et al, , 2008Calcagnotto et al, 2005). The larger similarity of the spermatozoa of Piaractus to other basal characid taxa (Malabarba & Weitzman, 2003) represented by Brycon and Salminus, seems to represent plesiomorphic features shared with non-serrasalmines.…”

“…Although Calcagnotto et al (2005) used a smaller number of genera (8) than Ortí et al (1996Ortí et al ( , 2008, the ingroup relationships found by the former authors are very similar, except for splitting the basal "pacus" clade, by positioning Colossoma and Mylossoma as a sister clade to Metynnis + (Pygocentrus + Serrasalmus), and Piaractus as the most basal genus. The relationships of serrasalmines and the Anostomoidea, however, are not supported by the great morphological diversity shown by those taxa.…”

“…Despite differences in the relative phylogenetic position of each genus, recent hypotheses are congruent in placing Piaractus, Mylossoma and Colossoma in a relative basal position among serrasalmines, and the genera Pygocentrus, Serrasalmus, Pristobrycon, and Pygopristis as the most derived taxa in a larger clade containing the remaining serrasalmine genera. Ortí et al (1996Ortí et al ( , 2008, using molecular data, found three major clades within serrasalmines: (1) a basal clade formed by Colossoma, Mylossoma, and Piaractus; (2) the "Myleus" clade, constituted by Myleus, Mylesinus, Tometes, and Ossubtus; and (3) the "piranha" clade, containing Serrasalmus, Pygocentrus, Pygopristis, Pristobrycon, Catoprion, and Metynnis. The genus Acnodon was placed as the sister taxon of clade (2+3).…”

“…Herein, spermiogenesis and spermatozoa of representatives of the three taxa of serrasalmines proposed by Ortí et al (1996Ortí et al ( , 2008 are described and compared with representatives of other characiform lineages. Phylogenetic implications and possible relationships of serrasalmines based characteres derived from spermiogenesis and spermatozoa structure are discussed.…”

New species of Metynnis Cope, 1878 (Characiformes: Characidae) from the rio Paraguay basin, Mato Grosso State, Brazil

“…Currently, 14 valid species are recognized within the genus (Zarske & Géry, 1999;. The most recent phylogenetic study on the genus Metynnis suggests that it is included in the "piranha" clade with the genera Serrasalmus, Pristobrycon, Pygocentrus, Pygopristis and Catoprion (Ortí et al, 2008).…”