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In an aquatic environment that most predators developed shark-like electroreceptive organs, what would be the counteractive measures against it?

Copper shells can disguise electric fields, but how it would evolve naturally? Biometal scales? Late-stage bamboo shark embryos cease all respiratory gill movements when exposed to predator-simulating electric fields, but there are no records of prey animals modulating their own bioelectrical signals to reduce predation risk. Therefore, a coherent electric stealth mode would be viable for living beings?

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    $\begingroup$ The same way animals consume, refine, and and excrete calcium to form their shells? $\endgroup$
    – DKNguyen
    Oct 11 '20 at 18:39
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    $\begingroup$ copper shells could be cool, but is there enough naturally-available copper? $\endgroup$
    – Sol
    Oct 11 '20 at 18:43
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    $\begingroup$ You're specifically interested in camouflage? Life tends to follow William of Ockham's Law of Parsimony (better known as "Occam's Razor"). Given all other things are equal, the simplest answer is usually correct. They'd develop defenses like spines and poison. Keep in mind that copper's not magic. You're thinking of a Faraday cage, but at best that only grounds the signals. Shells aren't grounded because they're sitting on the ground (or in the water). In that case, they're actually an antenna, which would make things worse. $\endgroup$ Oct 11 '20 at 20:00
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    $\begingroup$ I'd look into mimicry. Instead of trying to hide your bioelectric signals, amplify or modulate them so that you look like something that could take a shark in a fight. $\endgroup$
    – Cadence
    Oct 11 '20 at 20:03
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    $\begingroup$ Ooooh, @Cadence, that's a great idea. You should turn that into an answer. It might be the only legitimate one and it might be supported by existing creatures like electric eels. That would also lend to mating as females would be on the hunt for males exhibiting the greatest bioelectric signature (not unlike brilliant plumage). Yeah. That works an a bunch of different levels. $\endgroup$ Oct 11 '20 at 20:44
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Aquatic animals display a variety of modes and uses for electroreception. For best results, you're going to want an environment where electroreception is their primary means of both locating and identifying prey - as opposed to identifying targets by sight, then using electric signals at close range if the target is hiding. This would most likely be in extremely turbid waters where there is little available light.

Animals that use active electroreception - generating a low-level electrical field and measuring distortions in the field, similar to echolocation or active sonar - have a high degree of control over the frequency and modulation of the field. They can sense other animals using electroreception on similar frequencies and shift to avoid jamming each other, and some species use it for active communication.

With these sophisticated uses of electricity, it seems plausible that, in an environment with a lot of different species using active electroreception, prey species and smaller predators sense attackers' electric fields and respond with deimatic behaviors: startling and warning displays. This is similar to the patterning employed by butterflies, variously signaling (or bluffing) about their poisons or trying to mimic different predatory animals. Because these displays are about adding to a creature's electric field rather than removing it, they can use the same type of electrogenerating organs as other existing behaviors such as communication.

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