''Myloplus levis'', the Moon pacu, is a species of freshwater

ray-finned fish Actinopterygii (; ), members of which are known as ray-finned fish or actinopterygians, is a class of bony fish that comprise over 50% of living vertebrate species. They are so called because of their lightly built fins made of webbings of sk ...

belonging to the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Serrasalmidae The Serrasalmidae (serrasalmids) are a family of characiform fishes native to freshwater habitats of South America. They include more than 90 species. The name means "serrated salmon family", which refers to the serrated keel running along the ...

, which includes the pacus and piranhas. This fish is found in southern South America.

Taxonomy

''Myloplus levis'' was first formally described as ''Myleus levis'' in 1907 by the American

ichthyologists Ichthyology is the branch of zoology devoted to the study of fish, including bony fish (Osteichthyes), cartilaginous fish (Chondrichthyes), and jawless fish (Agnatha). According to FishBase, 35,800 species of fish had been described as of March 2 ...

Carl H. Eigenmann Carl Henry Eigenmann (March 9, 1863 – April 24, 1927) was a German-American ichthyology, ichthyologist of the late nineteenth and early twentieth centuries, who, along with his wife Rosa Smith Eigenmann, and his zoology students is credited wit ...

and

Waldo Lee McAtee Waldo Lee McAtee (21 January 1883 – 7 January 1962) was an American ecologist and ornithologist. He wrote extensively about the feeding habits of birds and mammals and described over 460 new species of insects. Early life and education Waldo L ...

with its type locality given as

Bahía Negra Bahía Negra is a district in the department of Alto Paraguay, Paraguay. Located on the right bank of the Paraguay River its population count is estimated to be around 2537, as of 2023. Location Bahía Negra is located in the northeastern ex ...

in Paraguay. The genus ''Myloplus'' is classified in the subfamily Myleinae, of the family Serrasalmidae, which is classified in the

suborder Order () is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between family and class. In biological classification, the order is a taxonomic rank used in the classification of organisms and recognized ...

Characoidei of the

order Order, ORDER or Orders may refer to: * A socio-political or established or existing order, e.g. World order, Ancien Regime, Pax Britannica * Categorization, the process in which ideas and objects are recognized, differentiated, and understood ...

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.: "Relationsh ...

Etymology

''Myloplus levis'' is classified within the genus ''Myloplus'', this taxon was originally proposed as a subgenus of ''Myletes'', this being a name which has been suppressed by the

International Commission on Zoological Nomenclature The International Commission on Zoological Nomenclature (ICZN) is an organization dedicated to "achieving stability and sense in the scientific naming of animals". Founded in 1895, it currently comprises 26 commissioners from 20 countries. Orga ...

as a

synonym A synonym is a word, morpheme, or phrase that means precisely or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are a ...

of ''

Alestes ''Alestes'' is a genus of freshwater ray-finned fishes belonging to the family Alestidae, known as the "African Characidae" as they are found exclusively on that continent. As suggested by that name, they Alestidae was formerly included in Char ...

''. The proposer of this genus,

Theodore Gill Theodore Nicholas Gill (March 21, 1837 – September 25, 1914) was an American ichthyologist, mammalogist, malacologist, and librarian. Career Born and educated in New York City under private tutors, Gill early showed interest in natural hist ...

, did not explain its etymology, it may be a combination of ''Mylo-'', a reference to disk-shaped body and a prefix used for similary shaped fishes in the same family, with ''plus'', which means "more", i.e., another ''

Myleus ''Myleus'' is a genus of serrasalmids from South America, where found in the Amazon, Orinoco and São Francisco basins, as well as the river basin of the Guiana Shield.Ota, R.P., Röpke, C.P., Zuanon, J. & Jégu, M. (2013): Serrasalmidae. ''In'' ...

''-like genus. 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 ...

, ''levis'', means "smooth", "polished" or "bald", an allusion Eigenmann and McAtee did not explain, nor is it obvious why they chose this name.

Description

''Myloplus levis'' has a maximum publsihed

standard length Fish measurement is the measuring of individual fish and various parts of fish anatomy, their anatomies, for data used in many areas of ichthyology, including Taxonomy (biology), taxonomy and fishery biology. Overall length Standard length (SL) is ...

of . Ot is dark brown in colour, lighter below 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 epithelia ...

. The fins are transluscent, apart from the dusky base of the

dorsal fin A dorsal fin is a fin on the back of most marine and freshwater vertebrates. Dorsal fins have evolved independently several times through convergent evolution adapting to marine environments, so the fins are not all homologous. They are found ...

and the black blotch on the margin of the anal fin.

Distribution and habitat

''Myloplus levis'' occurs in the

Paraguay Paraguay, officially the Republic of Paraguay, is a landlocked country in South America. It is bordered by Argentina to the Argentina–Paraguay border, south and southwest, Brazil to the Brazil–Paraguay border, east and northeast, and Boli ...

Paraná River The Paraná River ( ; ; ) is a river in south-central South America, running through Brazil, Paraguay, and Argentina for some ."Parana River". Encyclopædia Britannica. Encyclopædia Britannica Online. Encyclopædia Britannica Inc., 2012. Web. ...

drainage system, in Brazil, Bolivia and Paraguay. Pacus in the genus ''Myloplus'' are typically found in calm water close to banks in the main channels and in the vicinity of rapids.

References

*Jégu, M., 2003. Serrasalminae (Pacus and piranhas). p. 182-196. In R.E. Reis, S.O. Kullander and C.J. Ferraris, Jr. (eds.) Checklist of the Freshwater Fishes of South and Central America. Porto Alegre: EDIPUCRS, Brasil. {{Taxonbar, from=Q46638122 levis Taxa named by Carl H. Eigenmann Taxa named by Waldo Lee McAtee Fish described in 1907 Freshwater fish of South America