Taxonomy & naming
Asterophysus batrachus was described by Rudolf Kner in 1858 from Marabitanos on the Rio Negro, Brazil. The Catalog of Fishes lists it as valid in the family Auchenipteridae, the driftwood catfishes. It is sold under its scientific name; the hobby also uses gulper catfish for it.
The epithet is Greek for frog, batrachos, for the wide mouth.
Morphology
The mouth is huge and the body, head and gape are modified to engulf prey that approaches the catfish's own length. FishBase gives a maximum of 10 in SL.
Habitat
FishBase lists it from the Orinoco and Negro River basins of South America. It is a demersal tropical freshwater fish; no pH or temperature range is recorded.
Feeding
It is a predator on other fishes. Its large gape lets it take prey of nearly its own size, and in the aquarium it is fed live or whole frozen fish and large invertebrates; it will eat any tankmate that fits in its mouth.
Mating
The family Auchenipteridae fertilises its eggs internally, the male using a modified anal fin to inseminate the female. Observations of mating specific to Asterophysus batrachus are not recorded in the sources the atlas draws on.
Breeding
No spawning or fry observations are recorded for this species and it is not known to be bred in captivity.
In the aquarium
Keep it alone or with fish too large to swallow, in a roomy tank with driftwood caves and subdued light, since it is nocturnal and hides by day. Large prey it cannot finish can choke or injure it, so size the feeder fish to its mouth rather than its appetite. It is a specialist predator and not suited to a community tank of small fish.
Conservation
The IUCN Red List assessed Asterophysus batrachus as Least Concern in 2020. The sources the atlas uses record no specific threats.