Could fish (such as a moray eel) evolve chromatophores as advanced as a cephalopod's? Also how long would this take? I'm working on a speculative evolution project where moray eels are the only marine vertebrates. Some moray eels have evolved chromatophores to blend into their surroundings and 'hypnotize' crustaceans. Would the void of niches make this process any faster?
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$\begingroup$ Probably not "hypnotize" but "confuse". Most crustaceans have good or excellent vision, so that could still work. The more interesting question is: Why would hypnosis/confusing be more effective than a quick attack? Eels are fast, crustaceans typically are not. $\endgroup$– toolforgerCommented Dec 12, 2022 at 22:19
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$\begingroup$ Howdy Jayleth. Please remember (a) Stack Exchange has a one-and-only-one question policy. Asking more than one question in your post is an actual reason to close a question (click "close" and read "Needs More Focus"). (b) Insofar as we understand evolution, given enough time, anything can evolve. (c) Which doesn't mean much because what we understand about evolution and genetics doesn't scratch the surface. All of which is a long way of saying any choice you make is satisfactory because there might not be two people on the planet who could prove you wrong. $\endgroup$– JBHCommented Dec 12, 2022 at 22:26
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2 Answers
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Evolution doesn't work on given recipes, so there is no predefined time it will take to evolve or re-evolve a character:
- a random mutation or set of mutations needs to happen,
- the organism bearing it has to get an advantage from it to be favored in the competition for life, or at least not be at a clear disadvantage
- it must reproduce to carry on the mutation.
So, if by chance a mutate moray eel should be born today with chromatophores but then it would end up being fished by a human or eaten by a predator before having offspring, that mutation would be lost like tears in the rain.
Also related to the randomness of mutation, anything can happen, given enough time. Of course certain changes are more radical than others and would require more changes to not hamper the life chances of their bearer.
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The genetic evidence tells us that cephalopods evolved chromataphors somewhere in the Cambrian era, so it likely wouldn't take more than fifty million years for a creature to develop them.
Clarification: I'm not saying that you could expect an eel to develop chromatophors in any 50 million year period. That's like predicting how a hundred rolls of dice would fall. I'm saying that, should eels develop chromatophors, this is the time period over which you could expect it to develop.
Environmental niches exist, even if ecological ones don't. An unopposed species could readily populate an entire ocean over fifty million years, diversifying into literally billions of new species. They would become their own competition, and probably their own predators. A world where only one Chordate species exists is inherently unsustainable over those time periods.
I can't tell you what the lower bound of that is, since I don't know how many mutations it would take to produce the ability you're looking for. The more sophisticated the color control you desire, the longer it'll take to get there. If you want octopus level blending, it might take the full five hundred million years.
answered Dec 12, 2022 at 4:46
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$\begingroup$ I'm curious about this claim: "so it likely wouldn't take more than fifty million years for a creature to develop them." With only 1 example of a statistical distribution we are attempting to model (i.e. one planet), can we really say anything at all about the distribution? For instance. I got a new car and it got hit by another car on the same day. Thus, with this one example I model it as extremely likely for any new car I buy to be hit on the first day. Obviously a trivial example but it illustrates how undersampling the distribution can lead to improper results $\endgroup$– DerekGCommented Dec 12, 2022 at 14:22
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$\begingroup$ This is fiction, so we have to go by the anthropic principal, a.k.a., the rule of cool. If you're telling a story about your new car getting hit on the day you purchase it, then the probability is 100% that it's going to happen. It DOES happen and it HAS happened, therefore the probability that it will happen to YOU is immaterial. This doesn't suggest that you could set up a lab and expect those results. $\endgroup$ Commented Dec 12, 2022 at 17:47
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$\begingroup$ Right, I agree within the confines of the story that you can say whatever you want. You can say, "this trait evolved in this time". I simply disagree that we can say in general "likely would evolve this trait within this time" as this is a probabilistic statement, which we have insufficient evidence to generate. $\endgroup$– DerekGCommented Dec 12, 2022 at 17:59
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$\begingroup$ Yes, all we can say is that this one instance took X amount of time, therefore, should a creature follow that path, these are the time frames you'd be looking at. The idea that it couldn't happen without extremely broad speciation is, I think, the more important point. $\endgroup$ Commented Dec 12, 2022 at 18:22
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$\begingroup$ Actually, once chromatophores are established, adding more control is a relatively small step. All you need is an environment where blending in is an important survival trait, whether as prey or as predator. $\endgroup$ Commented Dec 12, 2022 at 22:15