ADW: Malapterurus electricus: INFORMATION

Geographic Range

The genus Malapterurus is found throughout western and central tropical Africa and the Nile River. They occur in all major freshwater systems including the Buzi Niger, Ogooué, Omo, Sanaga, Sabi-Lundi, Senegal, Shari, Zaïre and Zambezi River basins,as well as Lakes Albert, Chad, Kainji, Tanganyika and Turkana.

There are currently three species of Malapterurus. It is believed that M. electricus is restricted to the Nile River and Lake Chad (Moller, 1995).

Malapterurus minjiriya is known from the Niger River and Lake Kainji and M. microstoma is known from the Zaïre River basin. (Moller, 1995)

• Biogeographic Regions
• ethiopian
  • native

Habitat

Species in the genus Malapterurus are generally found among rocks or roots in turbid and/or black waters with low visibility; they favor sluggish or standing water. (Skelton, 1993)

• Habitat Regions
• freshwater

• Aquatic Biomes

• lakes and ponds

• rivers and streams

Physical Description

Species in the genus Malapterurus have a general body form that has often been described as a bloated sausage. When they swim, their soft, puffy bodies give tham the “appearance of a rather rigid sausage propelled by somewhat ostraciform movements” (Lissmann, 1958).

The body is elongate and cylindrical, and the head is slightly depressed. The eyes are small, the lips are rather thick, and the snout is rounded with widely separated nostrils. The gill openings are narrow and restricted to the sides. Malapterurus species have three pairs of barbels, and lack a dorsal fin. The pectoral, pelvic and caudal fins are rounded. The pectoral fins lack spines and have 8 to 9 fin rays. The pelvic fins have 6 fin rays and are inserted approximately halfway between the tip of he snout and the base of the caudal peduncle. The anal fin has 9 to 10 rays and is located anterior to the adipose fin, which is low and has a rounded posterior edge.

Malapterurus electricus can reach up to 1220 mm in total length (Skelton, 1993).

Species in Malapterurus are generally grayish-brown on the back and sides, fading to an off white or cream color on the ventral surfaces of the head and body. There are irregular black spots or blotches randomly distributed on the sides of the body. The posterior half of the caudal peduncle usually has a dark brown or black vertical bar and a cream vertical bar immediately anterior to it. The distal margins of the anal and caudal fins have a cream margin, and the base of the caudal fin has a cream region and a dark brown crescentic band immediately posterior to it.

The three different species of Malapterurus can be differentiated by the following key (after Sagua, 1987):

1a. Gill rakers on proximal two-thirds of first ceratobranchial, usually not exceeding 15; adipose fin short, sloped posteriorly M. minjiriya

1b. Gill rakers throughout entire length of first ceratobranchial, usually 15 to 23; adipose fin rounded, see 2a and 2b below.

2a. Mouth relatively narrow; snout relatively long M. microstoma

2b. Mouth relatively wide; snout relatively short, M. electricus

The most notable aspect of Malapterurus is its strong electrogenic ability. The electric organ, which is evolved from its pectoral muscle (Johnels, 1957), surrounds the body over most of the length of the fish and is capable of discharging up to 350 V (in a 500 mm fish; Keynes, 1957). (Johnels, 1957; Keynes, 1957; Lissmann, 1958; Sagua, 1987; Skelton, 1993)

• Other Physical Features
• bilateral symmetry

• Range mass

  0 to 20000 g

  0.00 to 704.85 oz

• Range length

  1220 (high) mm

  48.03 (high) in

Reproduction

Nothing much is known of the reproductive biology of M. electricus According to Polle & Gosse (1969), breeding pairs nest in holes some 3 meters in length excavated in clay banks in water 1 to 3 meters deep. (Poll and Gosse, 1969)

• Key Reproductive Features
• sexual
• fertilization
  • external

Lifespan/Longevity

• Average lifespan

  Status: captivity

  10 years

  AnAge

Behavior

Electric catfish are nocturnal and spend most of the day hiding under shelter. M. electricus is most active for a period of 4 to 5 hours after sunset as this is the time when peak hunting and feeding occurs (Belbenoit et al., 1979).

Because of their very small eyes, members of the genus Malapterurus hunt and navigate almost exclusively by using their EODs. Malapterurus electricus generates different kinds of EOD volleys (differing in the number, rate, and duration of volleys) depending upon the situation encountered.

There are five types of EOD volleys (Moller, 1995): the first type is associated with predation and feeding; the second one with defense, attack and protection; the third with defense, chase and exploration; the fourth with prey detection; and the fifth with intraspecific assessment.

Electric catfish are highly territorial, and defend against intrusions aggressively with their EODs. They adjust their discharge strategy depending upon whether the intruder is a conspecific or not. Against conspecifics, aggressive encounters start out with open mouth displays in one or both fish, followed by lateral displays. In lateral displays, the fish assume an ‘antiparallel’ positioning, swaying back and forth with arched bodies, and pushing and rubbing against each other. These displays last about 5 to 15 seconds and generally terminate the encounter. However, the encounters could escalate with more lateral displays and biting, which may be barbel or flank bites. In barbel bites, one or both fish grips the barbels of the other for 15 to 20 seconds while thrashing about, whereas in flank bites, one fish quickly turns its head and bites the flanks of the other, holding on for several minutes. Only during escalated encounters involving biting does either fish discharge (Rankin & Moller, 1986).

When faced with a larger than food-sized intruder of a different species, electric catfish do not utilize any of the ritualized displays such as the open-mouth and lateral displays, but instead utilize short EOD volleys (in contrast to the long predatory volleys), which are sufficient to drive intruders away (Bauer, 1968; Rankin & Moller, 1986). (Bauer, 1968; Belbenoit, et al., 1979; Moller, 1995; Rankin and Moller, 1986)

• Key Behaviors
• natatorial
• nocturnal
• motile
• territorial

Communication and Perception

• Perception Channels
• tactile
• chemical

Food Habits

Malapterurus electricus is a voracious piscivore (Sagua, 1979; Olatunde, 1984), hunting and stunning its prey using its paralyzing electrical organ discharge (EOD). It is an opportunistic feeder and will feed on the most readily available prey within its habitat. Electric catfish are able to consume prey up to half their size (Sagua,1979). The presence of high percentages of electric catfish with empty stomachs in wild-caught specimens studied suggests that these fish are slow-moving, deliberate feeders with infrequent, heavy meals (Sagua, 1979).

The EOD volleys involved in predation are long-lasting (up to 30 seconds long) and may comprise several hundred EODs. These feeding volleys are often preceded by low frequency “pre-volley” activity, which is believed to startle potential prey (Belbenoit et al., 1979). (Belbenoit, et al., 1979; Olatunde, 1984; Sagua, 1987)

• Primary Diet
• carnivore
  • piscivore

• Animal Foods

• fish

Economic Importance for Humans: Positive

Malapterurus electricus is eaten as food in parts of Africa. Along the shores of Lake Kainji, smoked electric catfish is a popular delicacy (Moller, 1995). Besides being a food fish, M. electricus is also occasionally encountered in the pet trade as an aquarium fish.

The electric organs of Malapterurus have been used in studies of neuronal metabolism, axonal transport, and transmitter release (e.g. Volknandt & Zimmermann, 1986), being particularly suited for this task because of their innervation by only one giant neuron (Janetzko et al., 1987). (Janetzko, et al., 1987; Moller, 1995; Volknandt and Zimmermann, 1986)

• Positive Impacts
• pet trade
• food

• research and education

Economic Importance for Humans: Negative

Aside from giving an unpleasant surprise to the occasional careless fisherman who handles it (the EOD an electric catfish generates is not known to be fatal to humans), there are no other known negative effects of M. electricus on humans.

• Negative Impacts

• injures humans

Electric catfish were known to the ancient Egyptians, being unmistakably depicted in bas-reliefs in tombs more than 5,000 years old. The ancient Egyptians called electric catfish “he who had saved many in the sea”, presumably because any electric catfish caught together with other fish would shock the fisherman through contact with the wet boating pole or the net, causing him to let go of his net and liberate his catch.

Preliminary data suggest that what is currently considered M. electricus consists of at least nine species (of which four miniature species with highly reduced electric organs from Zaïre possibly belong to a separate, undescribed genus) (Moller, 1995).

The phylogenetic relationships of the Malapteruridae are unclear. Howes (1985) proposed that they are most closely related to the Old World catfish family Siluridae, but Bornbusch (1991) questions this argument.

Malapterurus species have been reported to hiss like cats by Sorensen (1894), but this claim has never been substantiated.

Below is a list of additional resources on the web concerning the electric catfish:

For more scientific information on the electric catfish, visit the a href=”
http://www.fishbase.org/Summary/SpeciesSummary.cfm?genusname=Malapterurus&speciesname=electricus”>FishBase</A listing.

For a picture of the electric catfish on an ancient Egyptian bas relief, click a href=”
http://people.clemson.edu/~jwfoltz/WFB300/subjects/Ostario/catfish/Egyptian/egyptian.htm”>here</A. (Bornbusch, 1991; Howes, 1985; Moller, 1995; Sorensen, 1894)

Contributors

William Fink (editor), University of Michigan-Ann Arbor.

Nancy Shefferly (editor), Animal Diversity Web.

Heok Hee Ng (author), University of Michigan-Ann Arbor.

Glossary

Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

external fertilization

fertilization takes place outside the female’s body

fertilization

union of egg and spermatozoan

food

A substance that provides both nutrients and energy to a living thing.

freshwater

mainly lives in water that is not salty.

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

pet trade

the business of buying and selling animals for people to keep in their homes as pets.

piscivore

an animal that mainly eats fish

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

References

Balon, E., A. Coche. 1974. The Hague:

Bauer, R. 1968. Untersuchungen zur Entladungstätigkeit und zum Beutfangverhalten des Zwitterwelses Malapterurus electricus Gmelin 1789 (Siluroidea, Malapteruridae, Lacép. 1803). Z. Vergl. Physiol., 59: 371-402.

Belbenoit, P., P. Moller, J. Serrier, S. Push. 1979. Ethological observations on the electric organ discharge behaviour of the electric catfish, Malapterurus electricus (Pisces). Behav. Ecol. Sociobiol., 4: 321-330.

Bornbusch, A. 1991. Monophyly of the catfish family Siluridae (Teleostei: Siluriformes), with a critique of previous hypotheses of the family’s relationships. Zool. J. Linn. Soc., 101: 105-120.

Brichard, P. 1978. Notes on the nocturnal behavior of some rock inhabiting fish of Lake Tanganyika. Rev. Zoo. Bot. Afr., 92: 187-190.

Howes, G. 1985. The phylogenetic relationships of the electric catfish family Malapteruridae (Teleostei: Siluroidei). J. Nat. Hist., 19: 37-67.

Janetzko, A., H. Zimmermann, W. Volknandt. 1987. The electromotor system of the electric catfish (Malapterurus electricus): a fine structural analysis. Cell Tissue Res., 247: 613-624.

Johnels, A. 1957.

Keynes, R. 1957. Electric organs. Pp. 323-343 in M Brown, ed. New York:

Lissmann, H. 1958. On the function and evolution of electric organs in fish. J. Exp. Biol., 35: 156-191.

Moller, P. 1995. London:

Olatunde, A. 1984. Length-weight relationships and the diets of Malapterurus electricus (Gmelin) in Zaria. Rev. Zool. Afr., 98: 261-274.

Poll, M., P. Gosse. 1969. Revision des Malapteruridae (Pisces, Siluriformes) et description d’une deuxième espèce de silure électrique: Malapterurus microstoma sp. n. Bull. Inst. r. Sci. nat. Belg., 45: 1-12.

Rankin, C., P. Moller. 1986. Social behavior of the African electric catfish, Malapterurus electricus, during intra- and interspecific encounters. Ethology, 73: 177-190.

Sagua, V. 1979. Observations on the food and feding habits of the African electric catfish Malapterurus electricus (Gmelin). J. Fish Biol., 15: 61-69.

Sagua, V. 1987. On a new species of electric catfish from Kainji, Nigeria, with some observations on its biology. J. Fish Biol., 30: 75-89.

Skelton, P. 1993. South Africa:

Sorensen, W. 1894. Are the extrinsic muscles of the air blader in some Siluroidea and the ‘elastic spring apparatus’ of others subordinate to the voluntary production of sound?. J. Anat. Physiol., 29: 205-229.

Volknandt, W., H. Zimmermann. 1986. Acetylcholine, ATP and proteoglycan are common constituents of synaptic vesicles isolated from electric organs of electric eel and electric catfish as well as from a rat diaphragm. J. Neurochem., 47: 1449-1462.