The old saying goes: "Don't pretend to be something you're not." It's great advice for humans trying to navigate the complexities of identity and our place in society.
I'm lookin' at you, High School Me!
However, if you're a small creature that's constantly at risk of being eaten, pretending to be something else might not be so bad.
There's familiar examples of passive camouflage everywhere in the ocean. Sea Dragons look like loose, floating kelp; stonefish lie as unmoving as their namesakes on the bottom; grunt sculpins are nearly indistinguishable from a barnacle when they're still. There are even animals that actively camouflage to look like their environment. The many species of decorator crabs attach seaweed, sponges, hydroids, and any other flappy materials to their shell to blend in with their surroundings.
Microscopic hooks cover the crab's shell to facilitate camouflage
Courtesy: Ruth Hartnup via Flickr, and
Monique Salazar and W. Randy Brooks via Journal of Marine Science
But sometimes blending into the background isn't enough. Sometimes, you've got to do more than look the part. Sometimes you have to live your role to complete the illusion. Enter the cephalopods.
Octopus, squid, cuttlefish, and nautilus are all cephalopods (pronounced: sef-a-lo-pod). Cephs are probably the most intelligent and adaptable invertebrates in the world. A closer look at their anatomy can help us understand why. Cephalopods don't have claws or spines; they're not very fast; they have a sharp beak, but they have to get close to use it; and except for nautiluses cephs don't have a hard shell to protect their squishy, protein-rich bodies. So what do you do when you lack anatomical defenses? You get smart.
The most famous of this class to have the smarts to watch another animal and copy its behavior is the appropriately named mimic octopus (Thaumoctopus mimicus).
<in a nasally mocking voice> "watch another animal and copy its
behavior is the appropriately named mimic octopus"
Courtesy: Rickard Zerpe via Flickr
Dude, don't copy me that's ridiculous.
"Don't copy me that's ridiculous."
Courtesy: Avi Alpert via Flickr
<The following was typed very fast so the mimic octopus couldn't possibly copy it quick enough, and we can all actually learn something>
Mimic octopuses are found on sandy bottoms in the waters around Indonesia, the Philippines, and Papua New Guinea. These sandy and silty bottom habitats have few rocks, little animal growth, and minimal algae to hide among. While mimic octos can change their colors to match the background just as well as their cousins; movement tends to break the illusion. Other octopus species take advantage of rocky reefs or coral crevasses to slink along unnoticed while in motion, but mimics don't have that luxury. They also typically have to swim farther and more often than octopuses in other habitats because their prey isn't concentrated in a small area. A swimming octopus is very distinct, so mimics exactly copy the swimming behavior of flounder to conceal their true nature. They bend all their arms around and cluster them together so their eyes are sticking up in front of a big flat disk. As their arms trail, the ends flap just like the fins of a flatfish. The octopuses even stop and start moving with the same frequency as flounders all while hugging the contours of the rippled bottom.
We don't know why, but sometimes the mimic octopus will keep its distinct pattern while moving like a flounder and sometimes it will change to the fish's usual coloration.
Courtesy: Klaus Stiefel and Bernard Dupont via Flickr
The internet is full of reputed stories of mimic octos copying other species as well. While reports of mimic octopuses mimicking lionfish, sea snakes, and stingrays are out there we should remember that octopuses evolved entirely without our perceptions in mind. This means that what may clearly look like a lionfish to us, may look nothing like it to a grouper hungry for a bite of octopus arm. However, it may be that the mimics' strategy is just to look like "not an octopus", and whatever other creatures they see, they try and copy.
Amazingly mimic octopuses aren't the only species of octopuses to mimic other creatures. Living in the same waters as mimics the excitingly named "blandopus", which has which hasn't been formally described yet, also copies flounder. And if you Atlantic Ocean folks have been feeling left out, don't worry. The Caribbean has a copy-cat octo as well. Atlantic longarm octopuses (Macrotritopus defilippi) live in a very similar habitat to mimics and blandopus, and also engage in flat fish plagiarism.
Some species just have no regard for copyright law.
Courtesy: Wayne via Flickr
Clearly impersonating another animal is an effective way to avoid becoming someone's lunch. But can cephalopods use mimicry to catch their own prey?
Just off the coast of southern Brazil; in the southern summers of 1999, 2000, and 2001 a pair of scientists used lights shined from a boat to attract zooplankton. Light attractants like this are an important tool in many fisheries, particularly those for squid. Rodrigo Silvestre Martins and Jose Angel Alvarez Perez wanted to study how a community of predators and prey develop under these lights. Who's eating whom, how are they going about catching one another, and what could that mean for fisheries conservation? The researchers found that a column of animals, gradually increasing in size, formed under the lights. The smallest zooplankton were near the surface, and as you descended progressively larger predators lurked, waiting for a chance to strike at the prey above them.
Lurking in the shadows is pretty typical behavior for any predator, but one squid species' actions caught Martins and Perez by surprise. Atlantic brief squid (Lolliguncula brevis) are an estuary specialized squid that eat small schooling fish like anchovy and sardines. During Perez and Martins' study they watched brief squid regularly mimic the shape, color patterns, and swimming behavior of anchovies in order to get inside their schools without being noticed before striking.
I propose we call them "subterfuge squid" from now on.
Courtesy: NOAA Photo Library via Flickr
Now, squid aren't the only cephalopods to pantomime another animal in order to get close to prey. We've found one species of cuttlefish engages in a similar behavior to creep up on reef fish.
Pharaoh cuttlefish (Sepia pharaonis) are a widespread, small cuttlefish found throughout the warm waters of the Indian and Western Pacific Oceans. In 2011 a team of Japanese researchers noticed their cuttles doing something weird when they were placed in a large open tank for an experiment. The cuttlefish pushed together their upper pair of arms and colored them like eyes on the end of stalks. Then they set their other arms at odd, jointed angles and started twitching them, seemingly at random. Lastly they colored their mantle a shade lighter than all of their arms. The whole illusion came together to look exactly like a hermit crab.
In case the video widget doesn't work, click here to watch the pharaoh cuttles in action; it's astonishing. The research team thought maybe the cuttlefish were mimicking to protect themselves from potential predators when exposed in a large barren tank; kind of like mimic octopuses pretending to be other animals when they're moving in the open. But the scientists were curious if faking crabbiness (definitely the scientific term) could also help the cuttles catch prey like brief squid pretending to be anchovies.
So in 2013 they collected more pharaoh cuttlefish and put them in a tank with small tropical damselfish. The cuttles that pretended to be crabs got closer to the schools and caught twice as many fish as those that hunted while acting like cuttlefish! So yeah, I'd say that's an effective hunting strategy.
As we begin to look closer at cephalopods we're starting to understand just how diverse and seemingly intelligent their behavior is. Mimicries like these are just a sample of the ways octopus and their cousins use their adaptable camouflage. So maybe pretending to be something you're not isn't always bad. Maybe we shouldn't deal in absolutes all the time and recognize that there's advantages and disadvantages to lots of behaviors and life styles. There's a lot to be learned still about cephalopods, but there's also a lot to be learned from them.
References:
Hanlon, Roger T., Watson, Anya C., & Barbosa, Alexander, "A 'Mimic Octopus' in the Atlantic: Flatfish Mimicry and Camouflage by Macrotritopus defilippi", Biological Bulletin, 218: 15-24, Feb. 2010.
Accessed via: http://www.journals.uchicago.edu/doi/10.1086/BBLv218n1p15
Hanlon, Roger T., Conroy, Lou-Anne, & Forsythe, John W., "Mimicry and Foraging Behaviour(sic) of Two Tropical Sand-flat Octopuses of North Sulawesi, Indonesia", Biological Journal of the Linnean Society, Jan. 2008.
Accessed via: https://academic.oup.com/biolinnean/article/93/1/23/2701347
Accessed via: http://www.journals.uchicago.edu/doi/10.1086/BBLv218n1p15
Hanlon, Roger T., Conroy, Lou-Anne, & Forsythe, John W., "Mimicry and Foraging Behaviour(sic) of Two Tropical Sand-flat Octopuses of North Sulawesi, Indonesia", Biological Journal of the Linnean Society, Jan. 2008.
Accessed via: https://academic.oup.com/biolinnean/article/93/1/23/2701347
Martins, Rodrigo Silvestre & Perez, Jose Angel Alvarez, "Cephalopods and Fish Attracted by Night Lights in Coastal Shallow-waters, off Southern Brazil, with the Description of Squid and Fish Behavior", Revista de Etologia, Vol. 8 No. 1 Pg. 27-34, 2006.
Accessed via http://pepsic.bvsalud.org/pdf/reto/v8n1/v8n1a03.pdf
Okamoto et Al., "Unique Arm-flapping Behavior of the Pharaoh Cuttlefish, Sepia pharaonis: putative Mimicry of a Hermit Crab", Japan Ethological Society and Springer Japan, May 2017.
No comments:
Post a Comment