Well- it is a mucous created by the continal replacement of glandular cells know in the fishes skin that produce a glycoprotein which is called mucin. This when mixed with water forms the mucus that makes up the slime coat of fish.Fish with poorly developed scales tend to produce more of this slime coat.. The slime coat does threee basci things- it reduces turbulence for the fish when swimming by smotthing over the areas between the fishes scales-it helps regulate the internal/external ionic balance and the efficiecy of gases exchanged through the skins surface-ie-osmoregullation and it provides a slipery surface that in it's sloughing off prevents bacteria from attching themselves to the skin. Bacteria is simply washed away from the skin with this process. It also aids in acting as a wound bandage. Pretty important stuff........In some fish it retains moisture(lungfish) feeds fry(discus and some asian cat fish)) and can be toxic for a defence mechanicism and form a cocoon as in marine parrotfish for sleeping.It is the nest building material in labyrinth fishes and functions as a as a chemical alarm through the water from panic syndrome or injury.Stressed fish have a change in thier slime coat-either too much or too little of this protection will kill a fish.
One has to remember that in the areas of the amazon where a number of plecos exist there is little in the line of protein based foods. Aquatic insects and small inverts do not do well in the heavy current. Plecs are very adaptable to feeding on availiable food sources and one is the mucus coating of other fish. There is good anacdotal evidence of these fish doing this in the wild and plenty of evidence of these fish doing this in captivity. The closest taxonomic relitives of Loricariidae are the Trichomycteridae. There are several mucus feeding only trichomycterid catfishes. It really would not be a suprise to find that mucus feeding is a common feeding method in many Loricariidae catfishes. These fish are really not obligate herbivores. -Anne
One has to remember that in the areas of the amazon where a number of plecos exist there is little in the line of protein based foods. Aquatic insects and small inverts do not do well in the heavy current. Plecs are very adaptable to feeding on availiable food sources and one is the mucus coating of other fish. There is good anacdotal evidence of these fish doing this in the wild and plenty of evidence of these fish doing this in captivity. The closest taxonomic relitives of Loricariidae are the Trichomycteridae. There are several mucus feeding only trichomycterid catfishes. It really would not be a suprise to find that mucus feeding is a common feeding method in many Loricariidae catfishes. These fish are really not obligate herbivores. -Anne
