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he common comment of "A face only a Mother could love" would certainly fit our factsheet of the month for May 2023. A very special looking catfish that always turns heads when viewed for the first time. The catfish we are talking about of course is the "Gulper Catfish"  Asterophysus batrachus. This species is unusual among auchenipterids in having an enormous gape, a very distensible belly and, despite its short body, the ability to prey on large fishes.

Asterophysus batrachus

The mouth of this species is reminiscent of the Salmonidae (Salmon) family which is a good identification indicator. Very predatory which is unusual for a member of the Auchenipteridae family.

Abstract: The catfish Asterophysus batrachus (Auchenipteridae) has a huge mouth gape and is able to ingest very large prey. However, how it catches and positions such prey in its stomach remains unrecorded. We studied the predatory behavior of A. batrachus under aquarium conditions and found a novel feeding mode for piscivorous Neotropical catfishes. It uses its cavernous gape in a remarkable way, scooping up large unaware prey headfirst, then taking advantage of the fleeing response to further the prey’s advance into its stomach. Positioning of the prey results from additional escape movements into the very distensible belly of the catfish. The prey ends up folded in the stomach with its head and tail pointing towards the head of the predator (Zuanon, Jansen and Sazima, Ivan, 2005).

A fasting catfish occasionally takes in water, bulging its belly considerably (“belly ballooning”). After a while the fish expels the water entirely, along with a little mucus and a few small fragments of food. The wrinkled belly quickly regains its former shape. Because of its huge mouth, ability to swallow large prey and overall appearance, we name A. batrachus the ogre catfish (Zuanon, Jansen and Sazima, Ivan, 2005).

Asterophysus batrachus - close up of the wide mouth

This species is monotypic (one in the genus) and the subfamily of Auchenipterinae.

Ogre Catfish, Gulper Catfish

None

Auchenipterinae

South America: Orinoco and Negro River basins. Type locality: Marabitanos, Brazil.

25.0cm. (10ins)

23-28°c (73-83°f.)

10-13 branched anal fin rays. The anteriorly placed and elongate pharyngeal tooth plates, as well as the bands of villiform teeth on the premaxilla and dentary prevent prey from slipping out of the catfish’s mouth. The mouth has a very wide gape. Backward oriented suspensorium axis (formed by the hyomandibular-quadrate-articular bones); a loosely connected dentary symphysis; elongate and anteriorly placed pharyngeal tooth plates; slight mobility of the premaxillae along the symphysis; a narrow, v-shaped and anteriorly directed scapulocoracoid + cleithrum bridge, with a flexible connection of the opposite halves (i.e., not sutured); a well developed sphincter at the opening of the oesophagus.

You would need to choose tank mates very carefully as they will attack fish that are even larger than them and try and take them into their large expanding mouth. Would probably be better in a species tank on their own.

Not recorded

In sexually mature males there is a thickening to the first two rays of the anal fin.

Krill, shrimp, prawns, earthworms, daphnia and fish. As they get older they will need to be fed less as they will regurgitate their food if fed too much, so feeding every other day is best.

Anal fin: The median, unpaired, ventrally located fin that lies behind the anus, usually on the posterior half of the fish.
Caudal peduncle: The narrow part of a fish's body to which the caudal or tail fin is attached.
Cleithrum: The major bone of the pectoral girdle, extending upward from the pectoral fin base and forming the rear margin of the gill cavity, also: the principal bow-shaped bone of the prectoral girlde, dermal in origin, forming the rear margin of the gill cavity. It articulates dorsally with the supracleithrum and ventrally with the scapula and coracoid.
Coracoid: Middle and lower section of the pectoral girdle.
Dorsal fin: The primary rayed fin(s) on top of the body.
Lateral line: A sensory line, along the sides of the body.
Oesophagus: The oesophagus (gullet) is part of the digestive system, which is sometimes called the gastro-intestinal tract (GI tract). The oesophagus is a muscular tube. It connects your mouth to your stomach. When you swallow food, the walls of the oesophagus squeeze together (contract).
Premaxilla: In relation to the premaxilla (an upper jaw bone) e.g. premaxillary tooth band.

Asterophysus: Greek, aster = star + Greek, physa = tube, pipe, channel.
batrachus: From ‘batrachus’, a frog; frog-like.

Photo Credits

© Allan James @
Map: © Brazil_location_map.svg: NordNordWest.