A new kind of electric fish, described as having eel-like features, has been identified in a remote region of northern Guyana. The discovery was made by a team of researchers who found the undocumented genus of electric fish in the shallow waters of the upper Mazaruni River.
Named the Akawaio Penak, the creature was identified by tissue samples that the international team of scientists collected during a recent study, where the fish dwells, University of Toronto News reports.
The location contains numerous rivers and, for the most part, has remained unexplored for 30 million years. This isolation has led to a large amount of biological discoveries in the region.
“The fact this area is so remote and has been isolated for such a long time means you are quite likely to find new species,” said Nathan Lovejoy, professor at the University of Toronto Scarborough (UTSC) and a member of the research team.
The new genus of electric fish was revealed by DNA sequencing performed on samples from the fish. After the analysis was completed by Lovejoy’s team at UTSC, the researchers found that the fish was actually a unique, new genus of electric fish — the taxonomic classification level that is below a family but above a species.
While the Akawaio penak has an electric field, it is too weak to stun and is instead used for navigation. The fish had been found in the shallow, murky waters of the upper Mazaruni River, an area renowned for its biodiversity, but largely unexplored due to its remoteness.
The description of this new electric knife fish increases the total number of endemic genera and species in the upper Mazaruni, a region that is suffering freshwater habitat degradation as a consequence of gold-mining activities.
According to UTSC, the Akawaio penak is similar to other electric knife fish, featuring “a long organ running along the base of the body that produces an electric field.” The eel-like fish’s electric field isn’t strong enough to stun prey. Instead it uses it to travel through the water, communicate with other electric fish and locate objects. And seeing that it lives in the dark, cloudy waters of the upper Mazaruni River, the fish’s electric field assists it in successfully thriving in its habitat.
The fish was named after the Akawaio American Indians that live mainly in the upper Mazaruni. The discovery was published in the journal Zoolocia Scripta.
Generally, an electric fish is any fish that can generate electric fields. A fish that can generate electric fields is said to be electrogenic while a fish that has the ability to detect electric fields is said to be electroreceptive. Most electrogenic fish are also electroreceptive.
Electric fish species can be found both in the ocean and in freshwater rivers of South America (Gymnotiformes) and Africa (Mormyridae). Many fish such as sharks, rays and catfishes can detect electric fields and are thus electroreceptive, but they are not classified as electric fish because they cannot generate electricity. Most common bony fish (teleosts), including most fish kept in aquaria or caught for food, are neither electrogenic nor electroreceptive.
Electric fish produce their electrical fields from a specialized structure called an electric organ. This is made up of modified muscle or nerve cells, which became specialized for producing bioelectric fields stronger than those that normal nerves or muscles produce. Typically this organ is located in the tail of the electric fish. The electrical output of the organ is called the electric organ discharge (EOD).
Fish with an EOD that is powerful enough to stun prey are called strongly electric fish. The amplitude of the signal can range from 10 to 600 Volts with a current of up to 1 Ampere. Typical examples are the electric eel (Electrophorus electricus; not a true eel but a knifefish), the electric catfishes (family Malapteruridae), and electric rays (order Torpediniformes). Strongly electric marine fish deliver low voltage, high current electric discharges while freshwater fish have high voltage, low current discharges. This is because of the different conductances of salt and fresh water.
To maximize the power delivered to the surroundings, the impedances of the electric organ and the water must be matched. In salt water, a small voltage can drive a large current limited by the internal resistance of the electric organ. Hence, the electric organ consists of many electrocytes in parallel. In freshwater, the power is limited by the voltage needed to drive the current through the large resistance of the medium. Hence, these fish have numerous cells in series.
By contrast, weakly electric fish generate a discharge that is typically less than one volt in amplitude. These are too weak to stun prey and instead are used for navigation, object detection (electrolocation) and communication with other electric fish (electrocommunication). Two of the best-known and most-studied examples are Peters’ elephantnose fish (Gnathonemus petersi) and the black ghost knifefish (Apteronotus albifrons).
The EOD waveform takes two general forms depending on the species. In some species the waveform is continuous and almost sinusoidal (for example the genera Apteronotus, Eigenmannia and Gymnarchus) and these are said to have a wave-type EOD. In other species, the EOD waveform consists of brief pulses separated by longer gaps (for example Gnathonemus, Gymnotus, Raja) and these are said to have a pulse-type EOD.
(Sources: The Conversation, Wikipedia – The Free Online Encyclopaedia; International Business Times)
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