Thursday, April 20, 2017

[Ichthyology • 2017] Tometes siderocarajensis • A New Species of Tometes Valenciennes 1850 (Characiformes: Serrasalmidae) from Tocantins-Araguaia River Basin Based on Integrative Analysis of Molecular and Morphological Data


Tometes siderocarajensis 
Andrade, Machado, Jégu, Farias & Giarrizzo, 2017  

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.

 
Fig 1. Tometes siderocarajensis sp. nov. from Tocantins-Araguaia River Basin,
(a) MPEG 33922, holotype photographed alive, male, 338.0 mm SL;
(b) MZUSP 117052, paratype, preserved specimen, male, 341.3 mm SL.
Fig 4. Tometes siderocarajensis, paratypes, (a) INPA 52811, female, 227.3 mm SL,
 (b) ZUEC 12598, female, 328.0 mm SL. Preserved specimens.


Diagnosis: Tometes siderocarajensis sp. nov. is distinguished from all congeners by dense pigmentation on the distalmost portion of the pelvic-fin rays or the entirety of the fin (Fig 2A, Fig 2B) [vs. pelvic fin hyaline or pale, or with few scattered dark chromatophores along distal portion of rays (Fig 2C, Fig 2E)]. Additionally, it is distinguished from all, except from T. camunani and T. kranponhah, by having more circumpeduncular scale rows (39‒41 vs. 38 or less), and from T. kranponhah and T. trilobatus by having 1st and 2nd labial premaxillary teeth laterally spaced (Fig 3A) (vs. 1st and 2nd labial premaxillary teeth with lateral contact). The new species is further distinguished from T. trilobatus by having more perforated lateral line scales (74–84 vs. 58–72) and from T. makue by having more spines on ventral keel (11–17 prepelvic spines and 26–33 total spines vs. 0–9 and 10–23, respectively). Finally, Tometes siderocarajensis sp. nov. can be distinguished from T. lebaili by having a terminal to gently upturned mouth and invariably 5 dentary teeth (vs. a markedly upturned mouth and 6–7 dentary teeth).

Fig 7. Itacaiúnas River, Pará State, at Mosaic of Conservation Units of Serra dos Carajás, type locality of Tometes siderocarajensis


Etymology: The epithet siderocarajensis alludes to the locality ‘Serra and Carajás’, which is the largest high-grade iron deposit in the world. From the Greek‒Latin sidero means ‘iron’, and carajensis in allusion to the type locality. A toponymic adjective.

Geographic distribution: Tometes siderocarajensis is known to occur in the rapids of the Itacaiúnas River (Fig 7) and in its right-bank tributary, the Cateté River (average elevation of localities around 220 m a.s.l.), both located in the Mosaic of Conservation Units of Serra dos Carajás, Tocantins-Araguaia River Basin, State of Pará (Fig 8). In addition, T. siderocarajensis had its record confirmed in the Tocantins River based on specimens collected before the construction of the Tucuruí Hydroelectric Reservoir (INPA 52481), an area formerly known to contain many rapids but is currently flooded by the dam.


Marcelo C. Andrade, Valéria N. Machado, Michel Jégu, Izeni P. Farias and Tommaso Giarrizzo. 2017. A New Species of Tometes Valenciennes 1850 (Characiformes: Serrasalmidae) from Tocantins-Araguaia River Basin Based on Integrative Analysis of Molecular and Morphological Data. PLoS ONE. 12(4): e0170053. DOI: 10.1371/journal.pone.0170053

   

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