Wallago attu

In many areas, Wallago attu is found alongside the externally similar and related catfish species Wallagonia leerii. In Indonesia and Malaysia, both species are referred to as ikan tapah, and in English, both are sometimes called helicopter catfish. Popular accounts such as media reports, claims by fishermen, or local folklore stories, and even scientific publications, often confuse the two or are altogether unaware of the difference. Therefore, claims exist that Wallago attu reaches lengths of more than and weights of more than . Biologists, however, are firm that it does not grow beyond a length of roughly . It is thus assumed that reports about specimens even larger than that actually refer to Wallagonia leerii, which can grow to twice the length and several times the weight of Wallago attu. ==Distribution==

Wallago attu lives through large parts of South and Southeast Asia. Its range, however, seems discontiguous with a significant gap between the population inhabiting the Indian subcontinent and the one found across mainland and insular Southeast Asia. W. attu thus stands as an example for a species with a disjunct distribution. The second population occurs in Southeast Asia and encompasses Thailand, Laos, Cambodia, Vietnam, Malaysia and Indonesia. Here it inhabits the Mae Klong, Chao Phraya and Mekong drainages, as well as those of the Malayan peninsula and the islands of Java and Sumatra. It is absent from Borneo, which ichthyologist Tyson R. Roberts considers "surprising". The gap between the two populations is largely formed by the Salween and Tenasserim River drainages in Burma, where W. attu is not found. The reasons for this disjunct distribution are unknown. ==Biology and ecology==

As a large, predatory fish, W. attu maintains a largely piscivorous diet. Gut content analysis performed on specimens from the Godavari river in India shows that about 90 to 95% of the consumed food consisted of animal matter. Among the prey fishes most commonly found in the stomachs of Godavari river W. attu are razorbelly minnows (Salmophasia phulo), ticto barbs (Pethia ticto) and perchlets (Chanda nama), all of which are small species that reach maximum lengths of about . ==Possible species splitting==

The vast and disjunct distribution of W. attu has led to the assumption that it might in fact not be a single species. A preliminary bone-by-bone comparison of W. attu specimens from Southeast Asia and South Asia showed significant differences in their skeletal structure. It is thus assumed that pending further research W. attu may possibly be split into two or more species within the genus Wallago in the future. ==Cultural references==

According to Malaysian folklore, the descendant of a person called Tok Kaduk cannot eat and touch the fish because the legend says that a long time ago, Tok Kaduk caught this tapah. When he cut open its stomach, there was gold inside the fish so Tok Kaduk took the gold, stitched up the fish, and released it back into the river. From that time, if the descendant came in touch with the fish, their skin would become red and itchy until they went to Kg Tua, Lambor Kanan near Bota in Perak Tengah District of Perak, Malaysia to find the medicine. The medicine is the remaining gold from the fish, which has been kept to make the cure for the disease. Some say that the gold needs to be soaked in water and consumed by the patient as well as washing the areas that itch. Other stories have told that fish will devour the carcass of humans that have been buried in the water, and it will take the human's soul to the gods. The Malaysian town of Tapah and different tropical storms named Tapah have been named after this fish (or the identically named Wallagonia leerii). ==See also==