''Magosternarchus'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of weakly electric knifefish in the family

Apteronotidae The ghost knifefishes are a family, Apteronotidae, of ray-finned fishes in the order Gymnotiformes. These fish are native to Panama and South America. They inhabit a wide range of freshwater habitats, but more than half the species in the family ...

, containing two

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

. They are

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...

Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...

, occurring in large

river A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river. In some cases, a river flows into the ground and becomes dry at the end of its course without reaching another body of wate ...

channels in the Amazon River basin. Both species are unusual

benthic The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from ancient Greek, βένθος (bénthos), meaning "t ...

predator Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill th ...

s that specialize in biting off the tails of other knifefishes, and are characterized by their greatly enlarged jaws and teeth. Recent systematic studies indicate that both species should be included in '' Sternarchella'' instead of being placed in their own genus.

Taxonomy and etymology

The name ''Magosternarchus'' honors Dr.

Francisco Mago Leccia Francisco Mago Leccia (“Mago”) was born in Tumeremo, Bolívar State, Venezuela on May 21, 1931 and died in Puerto La Cruz, Anzoátegui State, Venezuela on February 27, 2004.Schaefer, Provenzano, Pinna & Baskin (2005) - ''New and Noteworthy V ...

, who has made many contributions to the study of gymnotiform knifefishes; the latter part of the name ''sternarchus'' is from the Greek ''sternon'' ("chest") and ''archos'' ("rectum"), referring to the forward placement of the urogenital opening in this group of fishes. The species name of ''M. raptor'' is from 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 ...

for "plunderer", referring to its tail-eating habits; the species name of ''M. duccis'' refers to the

Duke University Duke University is a private research university in Durham, North Carolina. Founded by Methodists and Quakers in the present-day city of Trinity in 1838, the school moved to Durham in 1892. In 1924, tobacco and electric power industrialist James ...

Center for Creative Ichthyology (DUCCIS), an

ichthyology 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, 33,400 species of fish had been described as of Octob ...

club. Based on several shared

skeletal A skeleton is the structural frame that supports the body of an animal. There are several types of skeletons, including the exoskeleton, which is the stable outer shell of an organism, the endoskeleton, which forms the support structure inside ...

traits, the closest relative of ''Magnosternarchus'' is believed to be the genus '' Sternarchella''. Several studies using both morphological and genetic data, published in 2013 and later, have strongly suggested that the genus should be merged into ''Sternarchella'' (making ''Magosternarchus'' a

junior synonym The Botanical and Zoological Codes of nomenclature treat the concept of synonymy differently. * In botanical nomenclature, a synonym is a scientific name that applies to a taxon that (now) goes by a different scientific name. For example, Linna ...

) and this has been followed by the Catalog of Fishes. Nevertheless,

FishBase FishBase is a global species database of fish species (specifically finfish). It is the largest and most extensively accessed online database on adult finfish on the web.

continues to recognize the two genera as separate.

Distribution and habitat

Both species of ''Magnosternarchus'' are believed to range widely in the

Amazon basin The Amazon basin is the part of South America drained by the Amazon River and its tributaries. The Amazon drainage basin covers an area of about , or about 35.5 percent of the South American continent. It is located in the countries of Bolivi ...

, including in the Rio Negro to at least above the confluence of the

Branco River The Branco River ( pt, Rio Branco; Engl: ''White River'') is the principal affluent of the Rio Negro from the north. Basin The river drains the Guayanan Highlands moist forests ecoregion. It is enriched by many streams from the Tepui highlands w ...

. ''M. raptor'' has been collected as far upstream as the lower Jutai River and as far downstream to the lower Xingu River; ''M. ducci'' has been collected as far upstream as

Ica River The Ica is a 220 kilometer long river in Peru which flows south from highlands in Huancavelica Region to the Pacific Ocean through Ica Region and passing the region's capital, the city of Ica. The river is normally dry during much of the year, ...

and as far downstream as Trombetas River. They are found in large, swift-flowing

whitewater Whitewater forms in a rapid context, in particular, when a river's gradient changes enough to generate so much turbulence that air is trapped within the water. This forms an unstable current that froths, making the water appear opaque and ...

and blackwater river channels, at least from shore, at depths of . They are absent from

beach A beach is a landform alongside a body of water which consists of loose particles. The particles composing a beach are typically made from rock, such as sand, gravel, shingle, pebbles, etc., or biological sources, such as mollusc shel ...

es, small

stream A stream is a continuous body of water, body of surface water Current (stream), flowing within the stream bed, bed and bank (geography), banks of a channel (geography), channel. Depending on its location or certain characteristics, a stream ...

s, and other marginal

habitat In ecology, the term habitat summarises the array of resources, physical and biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species habitat can be seen as the physical ...

Description

''Magosternarchus'' species are immediately recognizable by their large

jaw The jaw is any opposable articulated structure at the entrance of the mouth, typically used for grasping and manipulating food. The term ''jaws'' is also broadly applied to the whole of the structures constituting the vault of the mouth and serv ...

s, allowing for a wide gape, and their numerous, large, conical

teeth A tooth ( : teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, tear ...

. Both the

premaxilla The premaxilla (or praemaxilla) is one of a pair of small cranial bones at the very tip of the upper jaw of many animals, usually, but not always, bearing teeth. In humans, they are fused with the maxilla. The "premaxilla" of therian mammal has b ...

and the

dentary bone In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bone ...

are elongated, the former bearing two to three rows of teeth (numbering 9–14 in the outermost row) and the latter bearing three rows of teeth (numbering 15–19 in the outermost row). The deeply concave dorsal margin of the

opercle The operculum is a series of bones found in bony fish and chimaeras that serves as a facial support structure and a protective covering for the gills; it is also used for respiration and feeding. Anatomy The opercular series contains four bon ...

also serves to distinguish this genus. The

eye Eyes are organs of the visual system. They provide living organisms with vision, the ability to receive and process visual detail, as well as enabling several photo response functions that are independent of vision. Eyes detect light and conv ...

s are small and placed towards the top of the head. The body is similar to other ghost knifefishes, being laterally compressed with a long

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 ...

, a small

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 ...

, and no dorsal or

pelvic fin Pelvic fins or ventral fins are paired fins located on the ventral surface of fish. The paired pelvic fins are homologous to the hindlimbs of tetrapods. Structure and function Structure In actinopterygians, the pelvic fin consists of two en ...

s. There is a dorsal filament originating posterior to the midpoint of the body. The coloration is pinkish-white to translucent, with varying numbers of grayish-brown to black chromatophores on the upper sides of the body. The chromatophores are most concentrated at the dorsal midline, with the dorsal filament usually the darkest, and there are also thin, vertical lines of chromatophores on the

connective tissue Connective tissue is one of the four primary types of animal tissue, along with epithelial tissue, muscle tissue, and nervous tissue. It develops from the mesenchyme derived from the mesoderm the middle embryonic germ layer. Connective tiss ...

between the anal fin radial

muscle Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of muscl ...

s. The pigmentation on the nape is interrupted by a pair of pale, comma-shaped lateralis tubes. Tiny light dots of

electrosensory Electroreception and electrogenesis are the closely-related biological abilities to perceive electrical stimuli and to generate electric fields. Both are used to locate prey; stronger electric discharges are used in a few groups of fishes to stu ...

cell clusters are present over the back. The anal fin is clear, the caudal fin is clear to dusky, and the anal fin is clear in front and darkly

pigment A pigment is a colored material that is completely or nearly insoluble in water. In contrast, dyes are typically soluble, at least at some stage in their use. Generally dyes are often organic compounds whereas pigments are often inorganic compo ...

ed along the base in the back.

Biology and ecology

The only identifiable stomach contents of ''Magnosternarchus'' specimens have been the tails of other gymnotiform knifefishes. Most of the ''Magnosternarchus'' specimens thus far examined have also possessed regenerated tails. Like other apteronid knifefishes, ''Magnosternarchus'' is capable of producing a continuous weak electrical discharge for electrolocation and

electrocommunication Electroreception and electrogenesis are the closely-related biological abilities to perceive electrical stimuli and to generate electric fields. Both are used to locate prey; stronger electric discharges are used in a few groups of fishes to st ...

Species

FishBase recognizes two species in this genus, while both are placed in ''Sternarchella'' by Catalog of Fishes. *'' Magnosternarchus duccis''

Lundberg Lundberg is a surname of Danish language, Swedish origin. Lundberg means "wooded hill" or "mountain grove". Notable people with the surname include: A *Agneta Lundberg (born 1947), Swedish Social Democratic politician *Alfred Lundberg (1852–1935 ...

, Cox Fernandes &

Albert Albert may refer to: Companies * Albert (supermarket), a supermarket chain in the Czech Republic * Albert Heijn, a supermarket chain in the Netherlands * Albert Market, a street market in The Gambia * Albert Productions, a record label * Albert ...

, 1996 This species differs from ''M. raptor'' in having a markedly projecting lower jaw that often extends past and over the upper jaw and snout. The head is elongated and deep, with a concave dorsal profile. There are 204–212 fin rays in the anal fin, 14–16 rays in the pectoral fins, and 15 rays in a pointed caudal fin. The maximum reported length is . *'' Magnosternarchus raptor''

, Cox Fernandes &

, 1996 This species has an elongated, deep head with a moderately elongated, conical snout. The jaws are of equal length or the upper jaw is slightly longer. There are 180–197 fin rays in the anal fin, 14–16 rays in the pectoral fins, and 17 rays in a rounded caudal fin. The maximum reported length is .

References

{{Taxonbar, from=Q5302267 Apteronotidae Fish of South America Fish of Brazil Fish described in 1996 Freshwater fish genera Taxa named by James S. Albert