''Myloplus nigrolineatus'' is a species of freshwater fish in the serrasalmid

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

(family

Serrasalmidae The Serrasalmidae (serrasalmids) are a family of characiform fishes, recently elevated to family status. It includes more than 90 species. The name means "serrated salmon family", which refers to the serrated keel running along the belly of these ...

) of order

Characiformes Characiformes is an order of ray-finned fish, comprising the characins and their allies. Grouped in 18 recognized families, more than 2000 different species are described, including the well-known piranha and tetras.; Buckup P.A.: "Relationshi ...

. It is native to the

Amazon River The Amazon River (, ; es, Río Amazonas, pt, Rio Amazonas) in South America is the largest river by discharge volume of water in the world, and the disputed longest river system in the world in comparison to the Nile. The headwaters of t ...

basin in

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the southe ...

Description

Like other members of the serrasalmid family, ''Myloplus nigrolineatus'' is characterized by a deep,

elliptical Elliptical may mean: * having the shape of an ellipse, or more broadly, any oval shape ** in botany, having an elliptic leaf shape ** of aircraft wings, having an elliptical planform * characterised by ellipsis (the omission of words), or by conc ...

, and laterally compressed body, giving it a shape reminiscent of an elongated disc. The body ranges from 146 to 238 mm in length and 59 to 71 mm in depth. It has a slightly upturned, terminal mouth with two rows of molar-like teeth. Behind this main row of teeth is a pair of conical cutting teeth with a sharp surface on the front edge. The

cycloid scale A fish scale is a small rigid plate that grows out of the skin of a fish. The skin of most jawed fishes is covered with these protective scales, which can also provide effective camouflage through the use of reflection and colouration, as w ...

s are tiny and numerous, and the scales along the

lateral line The lateral line, also called the lateral line organ (LLO), is a system of sensory organs found in fish, used to detect movement, vibration, and pressure gradients in the surrounding water. The sensory ability is achieved via modified epithelial ...

are black colored due to high concentrations of black

chromatophores Chromatophores are cells that produce color, of which many types are Biological pigment, pigment-containing cells, or groups of cells, found in a wide range of animals including amphibians, fish, reptiles, crustaceans and cephalopods. Mammals and ...

. Overall color ranges from silver to lead-grey with scattered orange blotching. Breeding males will also display bright orange to red patches around the gill plates, pectoral fins, and on the anterior lobe of the

anal fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as se ...

. Breeding females show irregular orange and dark grey blotches scattered on flanks. A stout spine precedes the

dorsal fin A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through conv ...

, and the forked

caudal fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as se ...

has equal sized lobes.

Taxonomy

Classification

''Myloplus nigrolineatus'' is primarily distinguished from its cogeners by the black row of lateral line scales for which it is named. The intensity of this coloration can vary depending on which river within the Amazon basin a population occupies. Additional morphological characteristics that differentiate ''M. nigrolineatus'' from other members of its genus include the presence of 25 to 29 branched rays in the dorsal fin, and a greater number of lateral line scales (98-120 vs. fewer than 98 in other species).

Etymology

The generic name ''Myloplus'' comes from the

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

word ''mylos'' meaning grey mullet, and ''ploos'' meaning movement of a serpent. The

specific name Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...

''nigrolineatus'', and references the

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

word ''nigro'' meaning black, and ''lineatus'' meaning lined, and is derived from the dark colored lateral line characteristic of the species.

Distribution and habitat

''Myloplus nigrolineatus'' is widely distributed throughout the Amazon basin, where it inhabits slow-flowing backwaters and lakes. Specimens have been recorded from the

Aripuanã Aripuanã is a municipality in the state of Mato Grosso in the Central-West Region of Brazil. It is located on the banks of the Aripuanã River Aripuanã River ( pt, Rio Aripuanã) is a river in the Mato Grosso and Amazonas states in north-w ...

, Água Boa do Univini,

Nhamundá Nhamundá is the easternmost municipality in the Brazilian state of Amazonas. Its population was 21,443 (2020) and its area is 14,106 km².IBGE The Brazilian Institute of Geography and Statistics ( pt, Instituto Brasileiro de Geografia e ...

Tapajós The Tapajós ( pt, Rio Tapajós ) is a river in Brazil. It runs through the Amazon Rainforest and is a major tributary of the Amazon River. When combined with the Juruena River, the Tapajós is approximately long. It is one of the largest clearw ...

Tocantins Tocantins () is one of the 26 states of Brazil. It is the newest state, formed in 1988 and encompassing what had formerly been the northern two-fifths of the state of Goiás. Tocantins covers and had an estimated population of 1,496,880 in 20 ...

Jutaí Jutaí is a municipality located in the Brazilian state of Amazonas. Its population is 13,886 (2020) and its area is 69,552 km², making it the fifth largest municipality in Amazonas by area and the ninth largest in Brazil. Geography The mu ...

, Maués-Açu, and Uatumã rivers, as well as Pauapixuna lake (

Juruá River The Juruá River (Portuguese ''Rio Juruá''; Spanish ''Río Yuruá'') is a southern affluent river of the Amazon River west of the Purus River, sharing with this the bottom of the immense inland Amazon depression, and having all the characteristic ...

), Tapauá lake (

Purus River The Purus River (Portuguese: ''Rio Purus''; Spanish: ''Río Purús'') is a tributary of the Amazon River in South America. Its drainage basin is , and the mean annual discharge is . The river shares its name with the Alto Purús National Park and ...

), Serpa lake (

), Tracajá lake, and the Negro river basin. Despite the broad geographic range, this species is restricted to two specific habitat types. It requires either clear waters with very low levels of suspended sediments, or low ph and low sediment load blackwater habitats.

Diet

This species is

herbivorous A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthpart ...

, feeding mainly on

aquatic plants Aquatic plants are plants that have adapted to living in aquatic environments (saltwater or freshwater). They are also referred to as hydrophytes or macrophytes to distinguish them from algae and other microphytes. A macrophyte is a plant that ...

References

{{Taxonbar, from=Q96394560 Fish of South America Serrasalmidae Taxa named by Rafaela Priscila Ota Taxa named by Valéria Nogueira Machado Taxa named by Marcelo Costa Andrade Taxa named by Rupert A Collins Taxa named by Izeni Pires Farias Taxa named by Tomas Hrbek Fish described in 2020