Catfish of the Month Right Arrow October 2001

Fossil Catfish, Gællesæk-ålemalle (Denmark), Liver Catfish, Scorpion Catfish, Stinging Catfish - Heteropneustes fossilis   (Bloch, 1794)

Article © Julian Dignall, uploaded October 01, 2001.

For the first time I can remember we remain in Asia for this month's catfish. That, however, is where the similarity between this month's catfish and last month's (Horabagrus nigricollaris) ends. Last month's catfish was a new kid on the block, this months has been known to science almost as long as science has known catfish and the differences certainly do not stop there.

The fossil catfish is also commonly known as the liver, or stinging, catfish. Liver appertains to its general slivering red brown appearance - no Chianti involved! The name stinging catfish is even more well earned. Although it shares its colouration with the aforementioned bile creating organ, its ability to strike is surely its most fearsome feature. This is a venomous fish. Reports exist of fatal encounters between humans and it in the wild. Realistically it should come with a "buyer beware" sticker.

The average catfish aquarist would perhaps worry little about housing a venomous species. After all, we are the tool-users, used to hard-to-handle, spiky fish and this is just a fish maintained with tangible glass walls. In Calcutta, they are sold by the basketful in the local markets. Lots of housewives cook them regularly, with little concern for being stung. Perhaps it's easy to make too big a deal of the "lethal sting". That said, from various reports of this fish's activity in the wild, it is said to actually attack alien incursions into its world - seemingly unprovoked! The venom injected by punctures made possible by the fish's fin spines can cause death - a worrying prospect if this is a premeditated attack by the perpretrator. Not only that but it can happily cross damp land in search of aquatic pastures new. Acquire a brace of these fish and, trust me, water change day will never be the same again.

As with most things, a little knowledge goes a long way. Perhaps we should look at this species reported mode of reproduction before we jump to conclusions. This fish lays and guards its eggs in small pits in the local substrate. Adult fish, usually around or larger than the 300 mm mark, guard these inverted nests stoically and perhaps it is at this time that the bare-footed trespasser is really at risk. Certainly within the animal kingdom it is not unusual to encounter fanatical defence of a recent brood and shy, submissive retreat in its absence. Maybe this feature, more than others, has led to the banning of this fish's importation into certain parts of the world.

A venomous fish is a venomous fish. Regardless if wild or maintained in the aquarium, keepers should be aware of this fish and its attributes, and never resort to handling them directly. Be careful! If stung, as hot-as-you-can-stand water denatures the poison in the wound and hopefully allows the careless or very unlucky victim time to quickly seek professional medical help.

More recent hobbyist books cite two species of stinging catfish. This months catfish appears a larger and more commonly available species. The other apparently smaller species (H. microps) appears limited to the isolation of Sri Lanka and can be distinguished from our fish by its joined anal and caudal fin. In H. fossilis, the fins are distinct. This is a recent observation but has, even more recently, been refuted. According to this latest research (Pethiyagoda & Bahir, 1998) a sample of these fish from a Sri Lankan fishery yielded 2% of the Heteropneustes collected with conjoined fins. Concern was raised at the time to the rarity of these fish, but led to another line of thought. Confluence of unpaired fins has been observed occasionally in Clarias brachysoma (Günther, 1864) in Sri Lanka but these have been thought to be aberrant specimens. The authors examined living and preserved material and found that the animals had sustained injury to their caudal fins that, when regrowth occurred, caused the fins to join. I presume something in the Sri Lankan wild eats the tail fins of these fish yet it not present in mainland India to cause the same effect there. As many older hobbyist books confuse do not make the distinction based on the conjoined fins, they turn out to be, presently, correct.

Thus, the single species of Heteropneustes is the sole representative of both that genus and the entire family, thus making it the smallest of all catfish families. Although scientists see strong bone related reasons for including these species in the family Clariidae, other anatomical features of these remarkable fish keep it, presently, separate.

Reference : Heteropneustes microps, a junior synonym of H. fossilis (Osteichthyes: Heteropneustidae) Rohan Pethiyagoda and Mohomed M. Bahir, Journal of South Asian natural History Volume 3 • Number 1 • January, 1998

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