Sternarchogiton porcinum is a species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 of weakly electric knifefish

Knifefish

Knifefish may refer to several knife-shaped fishes:* The Neotropical or weakly electric knifefishes, order Gymnotiformes, containing five families:** Family Gymnotidae ** Family Rhamphichthyidae...

 in the family

Family (biology)

In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 Apteronotidae. It is native to deep river

River

A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...

 channels in the Río Huallaga

Huallaga River

The Huallaga River is a tributary of the Marañón River, part of the Amazon Basin. Old names for this river include Guallaga and Rio de los Motilones. The Huallaga is born on the slopes of the Andes in central Peru and joins the Marañón before the latter reaches the Ucayali River to form the Amazon....

, Río Napo, and Río Amazonas

Amazonas Region

Amazonas is a department of northern Peru bordered by Ecuador on the north and west, Cajamarca Department on the west, La Libertad Department on the south, and Loreto Department and San Martín Department on the east. Its capital is the city of Chachapoyas....

 in Peru

Peru

Peru , officially the Republic of Peru , is a country in western South America. It is bordered on the north by Ecuador and Colombia, on the east by Brazil, on the southeast by Bolivia, on the south by Chile, and on the west by the Pacific Ocean....

, and in the Río Orinoco in Venezuela

Venezuela

Venezuela , officially called the Bolivarian Republic of Venezuela , is a tropical country on the northern coast of South America. It borders Colombia to the west, Guyana to the east, and Brazil to the south...

. Many specimens once identified as S. porcinum from the Brazil

Brazil

Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...

ian Amazon Basin

Amazon Basin

The Amazon Basin is the part of South America drained by the Amazon River and its tributaries that drains an area of about , or roughly 40 percent of South America. The basin is located in the countries of Bolivia, Brazil, Colombia, Ecuador, Guyana, Peru, and Venezuela...

 and the Venezuelan Orinoco are now known to be a different species, S. preto

Sternarchogiton preto

Sternarchogiton preto is a species of weakly electric knifefish in the family Apteronotidae. It is native to large river channels and major side branches in the Amazon Basin, and is common in the Rio Tefé and the Rio Solimões to a depth of 14 m. It is found in both whitewater and blackwater habitats...

.

S. porcium is distinguishable from all other Sternarchogiton species by the straight dorsal profile of its laterally compressed head

Head

In anatomy, the head of an animal is the rostral part that usually comprises the brain, eyes, ears, nose and mouth . Some very simple animals may not have a head, but many bilaterally symmetric forms do....

. The eye

Eye

Eyes are organs that detect light and convert it into electro-chemical impulses in neurons. The simplest photoreceptors in conscious vision connect light to movement...

s are small and covered by a thin membrane

Biological membrane

A biological membrane or biomembrane is an enclosing or separatingmembrane that acts as a selective barrier, within or around a cell. It consists of a lipid bilayer with embedded proteins that may constitute close to 50% of membrane content...

. The mouth

Mouth

The mouth is the first portion of the alimentary canal that receives food andsaliva. The oral mucosa is the mucous membrane epithelium lining the inside of the mouth....

 is terminal, with the upper jaw longer than the lower. There are no teeth on the premaxilla

Premaxilla

The incisive bone is the portion of the maxilla adjacent to the incisors. It is a pair of small cranial bones at the very tip of the jaws of many animals, usually bearing teeth, but not always. They are connected to the maxilla and the nasals....

 and one row of 11 tiny conical teeth on the dentary. Both upper and lower pharyngeal tooth plates

Pharyngeal teeth

Pharyngeal teeth are teeth in the pharyngeal arch of the throat of cyprinids, suckers, and a number of other fish species lacking teeth.Popular aquarium fish such as goldfish and loaches have these structures. Members of the Botia genus such as clown loaches are known to make distinctive clicking...

 are present, bearing 8 and 10 teeth respectively. There is no sexual dimorphism

Sexual dimorphism

Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...

 in cranial morphology

Morphology (biology)

In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....

.

The body

Body

With regard to living things, a body is the physical body of an individual. "Body" often is used in connection with appearance, health issues and death...

 is compressed and knife

Knife

A knife is a cutting tool with an exposed cutting edge or blade, hand-held or otherwise, with or without a handle. Knives were used at least two-and-a-half million years ago, as evidenced by the Oldowan tools...

-shaped, with 4-6 rows of scale

Scale (zoology)

In most biological nomenclature, a scale is a small rigid plate that grows out of an animal's skin to provide protection. In lepidopteran species, scales are plates on the surface of the insect wing, and provide coloration...

s above the lateral line

Lateral line

The lateral line is a sense organ in aquatic organisms , used to detect movement and vibration in the surrounding water. Lateral lines are usually visible as faint lines running lengthwise down each side, from the vicinity of the gill covers to the base of the tail...

. The pectoral fins are broad and pointed, containing 15-18 soft rays. The long anal fin contains 182-216 rays. The tail

Tail

The tail is the section at the rear end of an animal's body; in general, the term refers to a distinct, flexible appendage to the torso. It is the part of the body that corresponds roughly to the sacrum and coccyx in mammals, reptiles, and birds...

 is compressed and moderately long, terminating in a small lance

Lance

A Lance is a pole weapon or spear designed to be used by a mounted warrior. The lance is longer, stout and heavier than an infantry spear, and unsuited for throwing, or for rapid thrusting. Lances did not have tips designed to intentionally break off or bend, unlike many throwing weapons of the...

olate caudal fin with 14-22 rays. The whip

Whip

A whip is a tool traditionally used by humans to exert control over animals or other people, through pain compliance or fear of pain, although in some activities whips can be used without use of pain, such as an additional pressure aid in dressage...

-like dorsal electroreceptive

Electroreception

Electroreception is the biological ability to perceive natural electrical stimuli. It has been observed only in aquatic or amphibious animals, since water is a much better conductor than air. Electroreception is used in electrolocation and for electrocommunication.- Overview :Electroreception is...

 appendage inserts in the posterior half of the body. The coloration is uniform white on the sides, tinged pink due to underlying capillaries. The back of the body and head are brown, with white-pink scale margins and white electroreceptor pits. The upper and lower jaws are white. The fins are hyaline

Hyaline

The term hyaline denotes a substance with a glass-like appearance.-Histopathology:In histopathological medical usage, a hyaline substance appears glassy and pink after being stained with haematoxylin and eosin — usually it is an acellular, proteinaceous material...

, becoming dark brown or grayish black at the margins. The maximum known length is 30 cm.

Like other apteronotids, S. porcium generates a weak electric field

Electric field

In physics, an electric field surrounds electrically charged particles and time-varying magnetic fields. The electric field depicts the force exerted on other electrically charged objects by the electrically charged particle the field is surrounding...

 for electrolocation and communication

Animal communication

Animal communication is any behavior on the part of one animal that has an effect on the current or future behaviour of another animal. The study of animal communication, is sometimes called Zoosemiotics has played an important part in the...

. This electric organ discharge has a fundamental frequency

Fundamental frequency

The fundamental frequency, often referred to simply as the fundamental and abbreviated f0, is defined as the lowest frequency of a periodic waveform. In terms of a superposition of sinusoids The fundamental frequency, often referred to simply as the fundamental and abbreviated f0, is defined as the...

 around 900 Hz

Hertz

The hertz is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon. One of its most common uses is the description of the sine wave, particularly those used in radio and audio applications....

 and has a waveform

Waveform

Waveform means the shape and form of a signal such as a wave moving in a physical medium or an abstract representation.In many cases the medium in which the wave is being propagated does not permit a direct visual image of the form. In these cases, the term 'waveform' refers to the shape of a graph...

 similar to that of S. nattereri

Sternarchogiton nattereri

Sternarchogiton nattereri is a species of weakly electric knifefish in the family Apteronotidae. It is native to the Amazon River system and feeds on sponges. Unlike other members of the genus Sternarchogiton, there is pronounced sexual dimorphism in S. nattereri, with reproductively mature males...

. Like S. nattereri, S. porcinum is able to modulate the frequency

Frequency

Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...

 and amplitude

Amplitude

Amplitude is the magnitude of change in the oscillating variable with each oscillation within an oscillating system. For example, sound waves in air are oscillations in atmospheric pressure and their amplitudes are proportional to the change in pressure during one oscillation...

of its EOD to produce communication signals categorized as "chirps" (high frequency elevation, short duration) and "gradual frequency rises" (low frequency elevation, long duration).