notion that they are notorious "parasites" that will readily take chunks out of tankmates (the use of the term is a misnomer, since biting chunks out of other fishes does not constitute parasitism
Just out of interest, is this how the two species known to exhibit this habit actually feed on a regular basis or is it because they are in close quarters in captivity ?
Is there a proper technical term for this behavior ? (besides hunger)
In that I kind of started the cetopsid topic off with my November COTM (Helogenes) entry, I figured that I'd make a little reply to your post. I am sure that HH can also follow up.
A good term for the cetopsids that will take chunks out of other fishes (or eat their way inside) would be voracious. As HH noted there are two species usually associated with such feeding behavior: Cetopsis candiru and C. coecutiens.
The first of these does appear to be a bit more extreme with the behavior. In the cetopsid revision mentioned by HH one of the specimens of this species was actually collected "...from inside a Brachyplatystoma...". They will attack fishes in nets and/or on lines (or possibly otherwise injured) and are noted to scavenge around areas of human habitation and were reported in such cases to feed on the by-products of fish preparation ("ofal and blood"). They are equally reported to feed on a wide variety of invertebrates. So they are definitely a carnivore actively exploiting a wide variety of foods.
C. coecutiens has, in a couple of studies, been listed as a piscivore without any further qualification. They are known to eat small fishes, shrimp and various aquatic and terrestrial insects. As with the above species, tethered, netted, on line, or otherwise injured fishes may also be attacked.
There are some other cetopsids that are reported, or suspected, to feed on other fishes that are caught in nets, injured, sick, dead, etc. These include Cetopsis gobioides and Cetopsis motatanensis.
From an aquarium point one might exercise care with some of the cetopsids and their tank mates. There is one report of a 93 mm Cetopsis othonops having a 40 mm characin in its stomach. Although it appears to feed mainly on insects and their larvae Denticetopsis seducta is apparently not beyond eating smaller fishes and there is one report that appears to relate to this species that does note it eating smaller, but reasonalbly sized, fishes which it is able to "roll up" in its stomach. As with many catfishes, it can be a case of let the keeper beware.
