Tometes

Tometes is a genus of rheophilic fish in the family Serrasalmidae found in northern South America.^[1] Three of the six species are restricted to river basins in the Guiana Shield, while T. makue is from the Rio Negro and Orinoco basins. All members of this genus are phytophagous. The genus name Tometes was coined in 1850 by Valenciennes in reference to the incisiform teeth.^[2]

When the type species of the genus, T. trilobatus, was described in 1850, it was placed in synonymy with Myleus setiger, the type species of the genus Myleus, which is why Tometes and Myleus were considered to be the same genus for a long time. It was just later that the two genera were revalitated and other specimen could be categorized in the genus Tometes.^[3]

Taxonomy

Even today the taxonomic classification of the Serrasalmidae is not an easy task. Many specimens are still placed in synonymy due to a lack of information and insufficient data bases. It was not long ago when it was discovered that Tometes and Myleus are two different genera but that Tometes, Myleus, Mylesinus and Ossubtus share a common ancestor. Typical characters of Tometes coincide with Mylesinus and Ossubtus specimen more than Myleus.^[3] It is further known that specimen of Tometes live in sympatry with other reophilic Serrasalmidae.^[1] Tometes species are also not to be mistaken with Pacus, a vegetarian fish, which is often sold as a vegetarian piranha in the corresponding countries. One can easily distinguish one from another by their very different composition of their dentition.^[4]

Description

This genus is strictly herbivorous fishes from the Serrasalmidae family. They reach a length of around 500 mm and a weight of up to 4 kg, although this can vary among species. The body color of these species is generally silver, showing a brighter color at the bottom side. Their name was given due to their incisiform teeth, which are thicker and lower than in the other related genera.^[3] Also the teeth are placed side by side, are weakly attached to the jaw and are primarily used for cutting leaves. Sexually mature male of Tometes differ from females by an additional anal-fin lobe, an elongated dorsal fin or a red pattern on the body.^[5]

Habitat and Ecology

Many valid species of Tometes were found in the left-bank tributaries of the lower Amazon basin, northeastern coastal rivers of the Guiana Shield, middle and upper Rio Negro and right-bank tributaries of the upper Rio Orinoco but T. ancylorhynchus and T. kranponhah are found in the coastal rivers of the Brazilian Shield.^[2] These species live in rapidly moving water with a rocky environment. A dense occurrence of Tometes larvae and juveniles in rapids around Podostemacae, the main food source of Tometes, suggests that there is a positiv rheotrophism in the larval stage. This association to their food source is correlated with their hyperspecificity, which can be seen in their vulnerability of the loss of rapids by the introduction of hydroelectric dams. In a cultural aspect rheophilic serrasalmids (Tometes, Myloplus and Mylesinus) are important in the tradition of local communities.^[1]

Species

There are currently 6 recognized species in this genus:

• Tometes ancylorhynchus M. C. Andrade, Jégu & Giarizzo, 2016 ^[2]
• Tometes camunani M. C. Andrade, Giarizzo & Jégu, 2013 ^[1]
• Tometes kranponhah M. C. Andrade, Jégu & Giarizzo, 2016 ^[2]
• Tometes lebaili Jégu, Keith & Belmont-Jégu, 2002 ^[6]
• Tometes makue Jégu, G. M. Santos & Belmont-Jégu, 2002
• Tometes trilobatus Valenciennes, 1850

References