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).
Range mass: 0 to 20000 g.
Range length: 1220 (high) mm.
Other Physical Features: bilateral symmetry