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Behavior

Fooled Ya! How marine animals stay hidden in plain sight

It’s April Fools’ Day!

Today’s the day when you try to prank people, convince them your lies are true, and generally make mischief and act sneakily! Animals have to act like it’s April Fools’ Day everyday, and it probably isn’t nearly as much fun since their lives depend on it. Predators sneak up on their prey. Prey hide from those who wish to eat them. It’s a harsh world out there, but luckily animals have a number of ways to camouflage themselves! Here are my 5 (well, actually 6) favorite examples of camouflage in the marine realm!

Brief Introduction

The type of camouflage an animal employs depends largely on the part of the ocean it lives in, but the general rule is to look like your surroundings! Whether that means blending in with corals and algae or becoming undetectable in the open ocean, it is best to make yourself invisible! Some organisms in open water (like jellyfish and comb jellies—ctenophores) are mostly transparent to avoid detection. Lots of fish have silvery scales that make them difficult to detect when viewed from the side. These methods of camouflage are cool, but I find the following examples really interesting!

The Runners-up and Winners of My “Coolest Camouflage” Contest

 

5th Place: Countershading

Grey Reef Shark. Source: Original author Fbattail, cropped by Chris Huh, available from Wikimedia Commons

Grey Reef Shark. Source: Original author Fbattail, cropped by Chris Huh Wikimedia Commons

Lots of marine animals, like dolphins and sharks, are darker on their back and have lighter bellies. This type of coloration is called countershading and it allows animals to blend into the surrounding water no matter which angle they’re viewed from. In the ocean, deeper is darker so, when viewed from above, these animals look dark like the depths of the sea, but from below, they appear lighter to match the brighter water and sky.

 

 

 

4th Place: Resembling surroundings

Broadnose Pipefish. Source: Miguel Mendez via Wikimedia Commons

Broadnose Pipefish. Source: Miguel Mendez via Wikimedia Commons

In shallow water habitats, organisms have a variety of options for blending in, depending on whether they’re on a reef, among algae, in seagrass, or on the substrate. Many creatures, like the pipefish, have evolved coloration and body form to match the habitat they spend most of their time in. Some, like the leafy sea dragon, also adopt behaviors that help them blend in even more. They drift along with the currents so that they sway along with the algae or seagrass they’re trying to impersonate. (Leafy Sea Dragon Video!)

 

 

3rd Place: Disruptive coloration

Four-Eye Butterflyfish. Source: Laszlo Ilyes, uploaded by Jacopo Werther, available from Wikimedia Commons

Four-Eye Butterflyfish. Source: Laszlo Ilyes, uploaded by Jacopo Werther, Wikimedia Commons

Ever wonder why so many animals seem to have large spots toward their tail? These “eyespots” are a type of disruptive coloration (high contrast non-repeating marks or patterns like spots or stripes, which break up the organism’s outline or conceal particular parts). Eyespots confuse predators about which end is the head versus the tail. When in conjunction with a dark bar through the real eye, eyespots cause predators to attack the tail end of their prey, giving the prey an opportunity to get away (possibly wounded, but alive). Other disruptive patterns include stripes that extend out to fins and call into question the true size and shape of the fish.

2nd Place: Self-Decoration

Sea Urchin Decorated With Shells. Source: Brocken Inaglory, Wikimedia Commons.

Sea Urchin Decorated With Shells. Source: Brocken Inaglory, Wikimedia Commons.

Some animals blend in by picking things up from their surroundings and decorating themselves. They use rocks, shells, algae, or even other animals (like anemones or other creatures with stinging capabilities)! Sea urchins and decorator crabs (Video! and Video!) are known to use this method. The sponge crab holds pieces of sponge on its back until they take root and grow on the shell.

 

 

 

And The Prize Goes To…

The following two types of camouflage blow my mind! They have to be a tie for First Place!

1st Place – B: Color/Pattern Changing

Peacock Flounder. Source: Brocken Inaglory, WIkimedia Commons. Note: All photos of the same fish taken within minutes of eachother.

Peacock Flounder. Source: Brocken Inaglory, Wikimedia Commons. Note: All photos of the same fish taken within minutes of eachother.

Through use of chromatophore cells, organisms can change their color or skin pattern to match their current background (or for signaling). Octopus skin has light-sensing capabilities that allow it to change color even when the skin is removed from the octopus! (Video!) Cuttlefish contract and expand skin layers which change how they reflect colors. They also control pigment-filled organs which they can flatten to produce patterns. One scientist argues that all their displays fall into three camouflage categories (uniform to match smooth textures, mottled for more complex settings, and disruptive—creating large patches of light and dark—to distract from their outlines) (Video!). Experiments have shown that cuttlefish are color blind, yet they can present themselves in any color or combination of colors. It is still unknown how that’s possible! Cephalopods aren’t the only creatures that do this though! Flounders and scorpionfish are also masters of disguise! And they, too, have chromatophores to thank!

P.S. Squid skin responds to sound/electrical stimulation (Video!).

1st Place – A: Counterillumination

Counterillumination. Source: Andrea Echeverria, Wikimedia Commons

Counterillumination. Source: Andrea Echeverria, Wikimedia Commons

Some open ocean and deep sea species, such as squid, use counterillumination. They have the ability to produce light on their underside so that when seen from below they match the ocean surface (Video!). Some species of squid manage this trick using photophores (organs that produce light) (Video!). The light can be produced from metabolic biproducts of digestion, by symbiotic bacteria, or in photocytes (special light producing cells).

If you think animals producing light is cool, check out these posts on biofluorescence, which may just be another way for some organisms to camouflage themselves (link and link)!

Concluding Remarks

These are only some examples of the ways that organisms in the ocean conceal themselves. I didn’t even touch on mimicry. There are other behaviors, modes of coloration, etc. that allow them to hide from predators or successfully stalk prey unseen. The ocean is an amazing place, with lots to discover! Sometimes, you just have to look very closely or know how creatures hide if you want to spot them!

Happy April Fools’ Day! Don’t get tricked by too many today!

Tell me in the comments: what is your favorite type of camouflage?

 

Links to More:

Great pictures of creatures camouflaging themselves!

Quiz Yourself! See how many cryptic animals you can find!

Lesson plan for teachers

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