Photograph by Ralph Lee Hopkins, National Geographic
The manta ray is a graceful swimmer, cruising the world’s temperate and tropical waters by flapping its large pectoral fins. When the mood strikes, however, those fins are used as wings to help launch the ray up to seven feet (two meters) in the air. Mantas have few predators—only large sharks—so it’s not known why they perform such aerial acrobatics. Because they sometimes leap in groups, scientists suspect the behavior may be a form of courtship—or simply a lot of fun.
Photograph by Robert Sisson, National Geographic
Females of this unusual octopus species sequester themselves in thin, translucent shells with which they drift across the open seas. Paper nautiluses, also called argonauts, secrete the shells to serve as cases for their eggs—but it has recently been discovered that they also function as air-trapping ballast tanks, which allow the cephalopods to hang effortlessly in the water column without sinking. This is the only species known to use surface air bubbles to effectively control the animals' buoyancy.
Blue Ocean Slug
Photograph by Daniel Coleman, My Shot
The blue ocean slug, a type of nudibranch, is a striking specimen with extraordinary hues that provide two types of camouflage. On the sea surface, the animal’s blue topside provides protection from hungry birds above, while its silver subsurface hides it from predatory fish looking up from below. The blue ocean slug is itself a formidable predator that feasts on dangerous animals like the Portuguese man-of-war. Not only is the slug unfazed by the man-of-war’s stinging cells, it ingests them and transports the toxic weapons internally to the ends of its own appendages for self-defense.
Photograph by Tim Laman, National Geographic
This colorful specimen, seen on a Polynesian reef, is one of several dozen formidable triggerfish species. The fish "locks up"—using a unique system of interlocking spines—to deter predators or to wedge itself into a hidey-hole. It got its name when fishermen realized they could "unlock" the fish by pressing on a small dorsal fin. These tough fish also defend their turf with a feisty attitude and a serious set of teeth, which are more commonly used to crunch sea urchins and shellfish.
Photograph by Catherine Fearn, My Shot
A lionfish peers through the glass of a Las Vegas aquarium. In the wild its beautiful, needle-like dorsal fins can deliver a painful and venomous sting. The formidable array of fins, combined with the fish’s color and generally prickly appearance, are meant to send a strong “stay away” message to predators in Indo-Pacific coral reefs.
Arctic Sea Cucumber
Photograph by Antonina Rogacheva, Shirshov Institute of Oceanology, Moscow
The Arctic sea cucumber was recently discovered in the deep sea and is now one of some 1,250 known sea cucumber species. Sea cucumbers are echinoderms related to sea stars and sea urchins. When threatened, the different species resort to a bizarre arsenal of defenses, which includes sliming their enemies with a web of sticky threads or confusing them by ejecting their own internal organs out of the anus.
Photograph by Jeff Rotman, The Image Bank/Getty Images
The aptly named porcupinefish is well known for its prickly method of defense. The fish’s body is covered with spines that lie flat until a threat appears. In the face of danger, the fish takes in water and balloons in size—causing its spines to stand straight up and create an extremely unappetizing appearance.
Red Snapping Shrimp
Photograph by Doug Perrine, SeaPics
A red snapping shrimp shows off its outsize claw on Gallows Reef in Belize. These crustaceans can close their giant claws so violently that they snap shut with a deafening sound used to stun prey. A short-lived bubble, created in the claw, is subsequently collapsed by pressures so strong they produce not only sound but also heat and even light—all in a matter of microseconds.
Photograph by Ken Lucas, Visuals Unlimited/Getty Images
The hagfish, also known as the slime eel, is a primitive bottom-dweller with no jaws, teeth, or stomach. The animal lacks even true eyes but it does have an incredible, and somewhat disgusting, defense mechanism.
When threatened, the hagfish secretes copious amounts of ropy, sticky, slippery, and snotty slime. This protein-and-sugar-based ooze is an unappetizing deterrent to predators. When the danger has passed, the hagfish cleans up by tying itself in a simple overhand knot and pulling its body through—scraping it clean.
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