A new species of Tometes Valenciennes 1850 (Characiformes: Serrasalmidae) from Tocantins-Araguaia River Basin based on integrative analysis of molecular and morphological data

Abstract

A new large serrasalmid species of Tometes is described from the Tocantins-Araguaia River Basin. Tometes siderocarajensis sp. nov. is currently found in the rapids of the Itacaiúnas River Basin, and formerly inhabited the lower Tocantins River. The new species can be distinguished from all congeners, except from T. ancylorhynchus, by the presence of lateral space between 1st and 2nd premaxillary teeth, and by the absence of lateral cusps in these two teeth. However, T. siderocarajensis sp. nov. can be differentiated from syntopic congener T. ancylorhynchus by an entirely black with mottled red body in live specimens, densely pigmented pelvic fins with a high concentration of dark chromatophores, and the presence of 39 to 41 rows of circumpeduncular scales (vs. silvery body coloration with slightly reddish overtones on middle flank during breeding period in live specimens, hyaline to slightly pale coloration on distalmost region of pelvic fins, and 30 to 36 rows of circumpeduncular scales). Additionally, molecular sequence shows that T. siderocarajensis sp. nov. is reciprocally monophyletic, and diagnosable from all congeners by having two autapomorphic molecular characters in the mitochondrial gene COI. The phylogenetic reconstruction still show that T. siderocarajensis sp. nov. is closely related to T. trilobatus. This is the first molecular study using an integrative taxonomic approach based on morphological and molecular sequence data for all described species of Tometes. These findings increase the number of formally described species of Tometes to seven. A key to the Tometes species is provided.

Phylogenomics of piranhas and pacus (Serrasalmidae) uncovers how convergent diets obfuscate traditional morphological taxonomy

“…The taxonomy and systematics of Serrasalmidae have a long-checkered past “fraught with confusion and instability” (Nico et al, 2018:172). Recent morphological studies have helped distinguish and diagnose a variety of valid genera and species (e.g., Pereira and Castro, 2014; Andrade et al, 2016a; 2016b; 2016c; 2017; 2018; 2019b; Ota et al, 2016; Mateussi et al, 2018; Nico et al, 2018; Escobar et al, 2019). The current study provides robust molecular support for recognizing three major lineages of Serrasalmidae at the subfamilial rank: Colossominae (pacus common to lowland, white water habitats), Myleinae (pacus common to upland clear- and black water habitats), and Serrasalminae (Metynnis and piranhas, cosmopolitan).…”

Relative size variation of the otoliths, swim bladder, and Weberian apparatus structures in piranhas and pacus (Characiformes: Serrasalmidae) with different ecologies and its implications for the detection of sound stimuli

“…We constructed a phylogenetic hypothesis (Figure ) based on the time calibrated molecular phylogeny (mt control region +10 nuclear genes) of Thompson et al (), the mt control region and 12S and 16S rRNA phylogenies of Ortí, et al (2008), and the mt cytochrome c oxidase subunit I gene phylogeny of Tometes spp. from Andrade et al (). We constructed a matrix with rate parsimony (mrp; Bininda‐Emonds, ; Sanderson, Purvis, & Henze, ) composite tree from three phylogeny nexus files that were constructed based on these published phylogenies.…”

“…We used the piranha clade topology obtained from Bayesian inference of the control region (1,130 bp) and 86 indel characters in Ortí et al (2008, Figure ). The third nexus file was constructed from the maximum likelihood tree obtained from two mitochondrial genes (COI and control region) in Andrade et al ().…”

“…Phylogenetic hypothesis of serrasalmid fishes from our study. Composite tree based on Ortí et al (2008), Thompson et al (), and Andrade, Machado, Jégu, Farias, and Giarrizzo () (see materials and methods for complete details). Branch length data are in millions of years (ma).…”

Structure and Function of the Armored Keel in Piranhas, Pacus, and their Allies

“…). The keel has been used by systematists to distinguish between certain species of serrasalmids, most notably herbivorous genera like Tometes, Myloplus, Myleus , and Utiarichthys (Pereira and Castro, ; Andrade et al, 2016 a,b, Andrade et al, ). The keel is highly variable: robust, stretching from anus to gular region in some lineages; while a curiously truncated, post‐pelvic remnant exists in some rheophilic taxa like Tometes and Ossubtus .…”