I have a penchant for cases of mimicry, not only because they served as some of the earliest evidence for natural selection in Darwin’s time, but also because they show how far natural selection can achieve “perfection”—that is, how far do developmental and physical constraints prevent the evolution of an “optimum phenotype.” The answer is that constraints don’t matter much.
There are few cases in nature where one can judge how “optimum” an adaptation is, and mimicry is one of them. (Sex ratio is another.) What it shows, as this post demonstrates, is that it can be remarkably precise; that is, natural selection is pretty good at molding animals (and some plants) to hide their true nature by evolving to resemble either another organism or their environment. The resemblance can be astonishingly precise.
Finally, many examples of mimicry are simply unexpected, cool, and stunning. The first one below was sent to me by Matthew Cobb who got it from a tweet by M.J. Walker from the Blue Planet Society. The photo is by Andrew Taylor.
One of these animals is a frogfish; the other is a sponge (yes, sponges are animals). If you look closely you can see which is which, but it may not be so easy for a predator or a prey item. (Frogfish are almost all predators.)
Frogfish, sometimes known as “anglerfish” are in the order Lophiformes and the family Antennariidae; 47 species are recognized.
Wikipedia has a good section on frogfish mimicry. I’ve reproduced it in the indented parts below, and inserted some pictures of different species of frogfish:
The unusual appearance of the frogfish is designed to conceal it from predators and sometimes to mimic a potential meal to its prey. In ethology, the study of animal behavior, this is known as aggressive mimicry. Their unusual shape, color, and skin textures disguise frogfish. Some resemble stones or coral while others imitate sponges, or sea squirts with dark splotches instead of holes. In 2005, a species was discovered, the striated frogfish, that mimics a sea urchin while the sargassumfish is colored to blend in with the surrounding sargassum.
Here’s the one, Antennarius striatus, that’s supposed to mimic a sea urchin:
Some frogfish are covered withalgae or hydrozoa. Their camouflage can be so perfect, that sea slugs have been known to crawl over the fish without recognizing them.
Here’s one that looks like an algae-covered rock:
Here’s another that looks like a sponge, hiding in a sponge:
For the scaleless and unprotected frogfish, the camouflage is an important defense against predators. Some frogfish can also inflate themselves, like pufferfish, by sucking in water in a threat display. In aquariums and in nature, frogfish have been observed, when flushed from their hiding spots and clearly visible, to be attacked by clownfish,damselfish, and wrasse, and in aquariums, to be killed.
Many frogfish can change their color. The light colors are generally yellows or yellow-browns while the darker are green, black, or dark red. They usually appear with the lighter color, but the change can last anywhere from a few days to several weeks. It is unknown what triggers the change.
To show how the mimicry works, here’s a sponge-mimicking frogfish nomming a cardinal fish. It’s fast!
Finally, a short clip of a frogfish feeding. It was filmed at 1000 frames per second and played at 10 frames per second, so this whole 17-second video represents 0.17 seconds in real time. Note how opening the mouth creates a suction that draws the prey in: