Looking at the serrations on the pectoral spine of a "Mystus gulio", which are very long and remind one of the barbs on a fish hook, i was wondering, what is the use of those?
Catfish with barbed/serrated pectoral spines always get stuck in hand nets when netted, making it harder for them to escape.
Adaptive value of pectoral spine serrations?
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beng
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Re: Adaptive value of pectoral spine serrations?
It just struck me that one possible use of barbs like that is to use as extrat sharp points with which to prick predators.
On one occasion when i had caught a "Mystus gulio", i was holding it by the body between thumb abd fore-finger using the pectoral spines to keep it from slipping through my hand, and it adducted its pectoral spines (moved them downwards towards its body) thus pressing against my fingers, and in so doing one of the barbs on the side of one of the spines poked my finger.
The amount of pain generated was more than i would expect from such a small pin prick, so i suspect that it may have some pain-producing chemical on its pectoral spines. At the same time it was not serious enough to prevent me from continuing to hold it, though i did soon after put it down.
Another feature of the barbs on the pectoral spines however, is that they are pointing back, away from teh tip, so that if one was to get unlucky and get a whole spine poked into one's hand, it would be difficult to pull it out. Surely such a feature is not advantageous to the fish, as it may get stuck to a predator or anything else that gets stuck on its spine (fish nets, plants, etc).
On one occasion when i had caught a "Mystus gulio", i was holding it by the body between thumb abd fore-finger using the pectoral spines to keep it from slipping through my hand, and it adducted its pectoral spines (moved them downwards towards its body) thus pressing against my fingers, and in so doing one of the barbs on the side of one of the spines poked my finger.
The amount of pain generated was more than i would expect from such a small pin prick, so i suspect that it may have some pain-producing chemical on its pectoral spines. At the same time it was not serious enough to prevent me from continuing to hold it, though i did soon after put it down.
Another feature of the barbs on the pectoral spines however, is that they are pointing back, away from teh tip, so that if one was to get unlucky and get a whole spine poked into one's hand, it would be difficult to pull it out. Surely such a feature is not advantageous to the fish, as it may get stuck to a predator or anything else that gets stuck on its spine (fish nets, plants, etc).
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beng
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Re: Adaptive value of pectoral spine serrations?
Also, when the fish was moving its pectoral spines, it made a grunting noise which could be heard as well as felt as vibrations while holding it.
Perhaps the barbs get the spine stuck in the throat of a predator that is swallong it whole, and when it finally pulls free the predator might spit out the fish?
Perhaps the barbs get the spine stuck in the throat of a predator that is swallong it whole, and when it finally pulls free the predator might spit out the fish?
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DeepFriedIctalurus
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I've wondered these same things myself, and my slightly scientific conclusion was it might be a bit less-specialized defense along the lines of a honeybee's stinger.
Sure, a catfish may actually get away & survive unlike the bee...but maybe the catfish that does die or get eaten in the process of defending itself w/ it's spines may have still succeeded in preventing that individual predator from using said catfish as a food source in the future. Sacrificing itself in the name of general predator deterrance is something alot of living things seem to be willing to do, I'm sure Dendrobates dartfrogs don't escape many encounters w/ unknowing predators..
Sure, a catfish may actually get away & survive unlike the bee...but maybe the catfish that does die or get eaten in the process of defending itself w/ it's spines may have still succeeded in preventing that individual predator from using said catfish as a food source in the future. Sacrificing itself in the name of general predator deterrance is something alot of living things seem to be willing to do, I'm sure Dendrobates dartfrogs don't escape many encounters w/ unknowing predators..