black ghost knife fish
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The black ghost knifefish (''Apteronotus albifrons'') is a
tropical The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in the Southern Hemisphere at S. The tropics are also referred to ...
fish Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of ...
belonging to the
ghost knifefish 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 ...
family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...
( Apteronotidae). They originate in freshwater habitats in South America where they range from
Venezuela Venezuela (; ), officially the Bolivarian Republic of Venezuela ( es, link=no, República Bolivariana de Venezuela), is a country on the northern coast of South America, consisting of a continental landmass and many islands and islets in th ...
to the
Paraguay Paraguay (; ), officially the Republic of Paraguay ( es, República del Paraguay, links=no; gn, Tavakuairetã Paraguái, links=si), is a landlocked country in South America. It is bordered by Argentina to the south and southwest, Brazil to th ...
Paraná River, including the Amazon Basin. They are popular in aquaria. The fish is all black except for two white rings on its tail, and a white blaze on its nose, which can occasionally extend into a stripe down its back. It moves mainly by undulating a long fin on its underside. It will grow to a maximum length of . and can grow bigger depending on the type of food. Black ghost knifefish are nocturnal. They are a weakly electric fish which use an
electric organ An electric organ, also known as electronic organ, is an electronic keyboard instrument which was derived from the pump organ, harmonium, pipe organ and theatre organ. Originally designed to imitate their sound, or orchestral sounds, it has sinc ...
and receptors distributed over the length of their body in order to locate insect larvae.Nelson M. E. & MacIver M. A. (1999). "Prey capture in the weakly electric fish ''Apteronotus albifrons'': sensory acquisition strategies and electrosensory consequences". ''J. Exp. Biol.'' 202: 1195–1203
pdf
/ref> The black ghost knifefish natively lives in fast moving, sandy bottom creeks in a
tropical The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in the Southern Hemisphere at S. The tropics are also referred to ...
climate. South American natives believe that the ghosts of the departed take up residence in these fish, hence the name. The black ghost knifefish is a weakly electric fish as a result of the electromotor and electrosensory systems it possesses. While some fish can only receive electric signals, the black ghost knifefish can both produce and sense the electrical impulses. Electrogenesis occurs when a specialized electric organ found in the tail of the fish generates electrical signals, which are thus called electric organ discharges (EODs). Then, for these EODs to be sensed by the fish,
electroreception 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 ...
occurs when groups of sensory cells embedded in the skin, known as electroreceptor organs, detect the electrical change. The EODs are used for two major purposes:
electrolocation 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 ...
and communication. The kind of EOD produced can be used to distinguish between two types of weakly electric fish: the pulse-type and the wave-type. The black ghost knifefish are considered to be the latter type, because they can continuously generate EODs in small intervals. Wave-type EODs have a narrow power spectra, and can be heard as a tonal sound, where the discharge rate establishes the fundamental frequency. By emitting its own continuous sinusoidal train of EODs, the fish can determine the presence of nearby objects by sensing perturbations in timing and amplitude of electric fields, an ability known as active electrolocation. The particular organs used to sense the self-generated high-frequency EODs are tuberous electroreceptor organs. On the other hand, when low-frequency electric fields are generated by external sources instead of the fish itself, a different class of electroreceptor organs is used for this passive electrolocation, called ampullary organs. Therefore, the black ghost knifefish uses an active and a passive electrosystem, each with its own corresponding receptor organs. The fish can also use a mechanosensory lateral line system, which detects water disturbances created by the motion of the fish's body. As nocturnal hunters, the fish can rely on all three systems to navigate through dark environments and detect their prey. Each species has a characteristic EOD baseline frequency range, which varies with sex and age within the species, as well. The baseline frequency is maintained to be almost constant at stable temperature, but will usually be changed due to the presence of others of the same species. Such changes in frequency relevant to social interaction are called
frequency modulation Frequency modulation (FM) is the encoding of information in a carrier wave by varying the instantaneous frequency of the wave. The technology is used in telecommunications, radio broadcasting, signal processing, and computing. In analog fre ...
s (FMs). The role these FMs have in communication is significant, as black ghost knifefish have developed
jamming avoidance response The jamming avoidance response is a behavior of some species of weakly electric fish. It occurs when two electric fish with wave discharges meet – if their discharge frequencies are very similar, each fish shifts its discharge frequency to inc ...
s, which are behavioral responses that avoid the overlapping of EOD frequencies between
conspecific Biological specificity is the tendency of a characteristic such as a behavior or a biochemical variation to occur in a particular species. Biochemist Linus Pauling stated that "Biological specificity is the set of characteristics of living organis ...
individuals to prevent sensory confusion. Moreover, a study was conducted that focused on
sexual dimorphism Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most an ...
in electrocommunication signals. Female black ghost knifefish generate EODs at a higher frequency than the males, an FM which can be used for gender recognition. A study found the subordinate black ghost knifefish exhibited noticeable gradual frequency rises (GFRs) in their EODs whereas the dominant fish did not, supporting the researchers' hypothesis that GFRs during communication are indicative of submissive signals. It is possible to use a device to convert a captive fish's electrical signals into audible sound, allowing listeners to hear the fish "talk". The Bakken Museum in Minneapolis has a display with such a device and a black ghost knifefish.


References

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Further reading

* MacIver M. A., Patankar N. A. & Shirgaonkar A. A. (2010). "Energy-Information Trade-Offs between Movement and Sensing". '' PLoS Computational Biology'' 6(5): e1000769.


External links


Ikan Black Ghost

The MacIver Lab Homepage

Black Ghost Knife Fish, ''Apteronotus albifrons'' (Linnaeus, 1766)
BdFISH Bangladesh Fisheries Information Share Home (BdFISH) is a global online database of information about fish species of Bangladesh. It is the largest and most extensively accessed online database on fishes of Bangladesh on the web. Over time it has ...
* {{DEFAULTSORT:knifefish, ghost, black black ghost knifefish Fish of Venezuela Fish of the Amazon basin black ghost knifefish Taxa named by Carl Linnaeus