#Chanallabes apus

[aquariuminfobureau]

Sometimes I am asked which fish they might purchase, along with the mudskippers, that has a true affinity for life on land, as opposed to simply possessing the ability to breathe air, or draw over the land. Top of the list must be two African catfishes of genus Gymnallabes and Chanallabes, known as the eel catfishes. (There are other species in these genera, but it is known, or assumed, that traded eel catfishes are of these two species.) These genera are related to the African and Asian walking catfishes, of the genus Clarias - but these leave the water only under environmental stress. Gymnallabes and Chanallabes are true fish, but they are habitually amphibious by their nature and prefetence. The entire clade Clariidae to which they belong, and its sister genus Heteropneustes, are bestowed gill arches modified into a novel respiratory organ, which is an evolutionary adaptation for breathing atmospheric air. Gas exchange also occurs through the skin of clariid catfishes.

Gymnallabes typus is native to West Africa, east to Cameroon, and is a relative of the Central African Chanallabes apus. These two catfish species are very similar, and G. typus is often incorrectly labelled in the trade as Chanallabes apus, which some people mistakenly think is the only species of eel catfish. One difference between the two species and their genera, is that Chanallabes catfish have lost their pectoral fins, and Gymnallabes have retained them. Of the two species, G. typus reaches only 30 centimetres or 12 inches long, and the larger C. apus can grow 7 centimeters or nearly 3 inches longer than this. Their body shape is strikingly eel-like, a similarity of form and function that formed the basis for the common name broadly applied to all such catfishes in English.

Eel catfishes routinely leave the water to forage amid damp leaf litter, in addition to frequenting forest streams, ditches, and swamps. Because these catfishes regularly seize insect prey when they foray on land, their ability to exploit terrestrial prey resources, has fascinated scientists interested in how our own Palaeozoic ancestors, quite independently of any true fish, became land animals. Needless to say, the aquaterrarium for these remarkable species should contain plenty leaves, such as Indian almond. Eel catfishes have evolved to burrow and hide among the leaf litter of humid African forests, both in and out of the water, and they will readily take advantage of aquarium decorations, as a place to shelter from bright light and stressful encounters. The land portion they are provided, must obviously remain damp.

Ideally the water pH should reflect the habitats of wild eel catfish. The rivers and streams of West Africa are more soft and acidic, with a typical pH value of 6 to 7, than are those of Central Africa, which hover around a value of 7. Although it is doubtful that the difference between these values, which are generalizations based on their geographical origins, would have any effect on the health of either species. Precaution must be taken that these slender and air breathing fishes, do not escape through holes in the lid. These burrowing, nocturnal animals have poor eyesight and are averse to bright light, so will be observed more often if the lighting is dim. Fortunately these catfish seem to do fine, when housed at normal, tropical aquarium temperatures. In the aquaterrarium they show disinterest in any animal that is not bothering them, and that they do not assume is potential prey.

Because these fish have small heads and gapes, only very small ornamentals could be at risk from these catfish. On principle, a wide range of mutually indifferent animals can thus share the land and water portions of the same aquaterrarium, without nasty accidents or incidents. One further consideration is that faster swimmers and boisterous feeders, might outcompete these benthic catfish, for the food that is provided to the whole aquarium community. Because eel catfish are essentially insectivores, their feeding is unprobematic. Food might be supplied for them in a frozen form, or as sinking tablets composed of appropriate ingredients. Although eel catfish have reportedly acclimatised in the aquarium to bolder, diurnal feedings, they might not cooperate, especially if they are recently imported from Africa.