Protect and Prosper

Part of the Life at the Limits exhibition.

Some insects live only a few hours, while a tortoise might trundle along for centuries. Humans rarely make it past 100 but there are trees older than the Great Pyramid. A few creatures even gain years through suspended animation, a sort of reversible death. How is it that lifespans can vary so wildly? And is death truly inevitable? 

Though life spans might differ, one of the surest ways to stay alive is to be able to defend against predators. Plants and animals have evolved an astonishing array of adaptations to keep themselves safe. Defenses like spines and armor tend to evolve again and again in unrelated species—a phenomenon called convergent evolution.

Master of Mimicry

One common and effective means of protection is to appear bigger, meaner, or more threatening than you really are. The mimic octopus (Thaumoctopus mimicus) takes this defense to a new level with its ability to seemingly transform into multiple, different species at will! It’s so hard to spot, the species was unknown until 1998. 

The skin of the mimic octopus creates colors and patterns like a video screen, and its boneless body can take on almost any shape. These amazing adaptations help it scoot over bare mud in broad daylight. Most animals that dare to do this have poisonous weapons; the mimic octopus doesn’t. Instead, it scares off predators by mimicking more toxic neighbors like the banded sea snake and the lionfish.

Look closely at the illustration below, and you’ll see the harlequin jawfish alongside the octopus on the right. This species imitates the mimic, sticking close to the octopus to avoid detection while swimming outside its burrow.

Mimic Octopus
The mimic octopus can pretend to be a variety of poisonous sea animals, scaring off predators.
(C) AMNH/5W Infographics/P. Velasco

Strength in Scales:

Named for J. R. R. Tolkien’s fearsome dragon Smaug, the giant dragon lizard (Smaug giganteus) has protective plates on its back, but a soft underbelly. Unlike Tolkien’s dragon, it is only 6 to 7 inches long, but these bony plates, called osteoderms, help to protect it from larger predators.

Smaug Lizard
Bony plates make predators think twice before attacking the Giant Dragon Lizard.
Wikimedia/ Eric Johnston

Hard to Hurt

Tardigrades live nearly everywhere, from bubbling hot springs to holes in the Antarctic ice, mountaintops to deep-sea trenches. When the going gets particularly tough, they enter a state called cryptobiosis—hidden life—and while it lasts, tardigrades are just about invincible.

How tough are they? Send them into the vacuum and cosmic radiation of space and most bounce back. Subject them to atmospheric pressure 600 times that at sea level and they pick up right where they left off. Chill them to -328˚ F (-200˚ C) for 20 months: no problem. The tiny invertebrates don’t even age during cryptobiosis, adding months, sometimes years, to their lifespan.

Tardigrades can enter a state known as 'cryptobiosis' in which they are nearly impossible to kill. 
© Eye of Science/Science Source 

New Lease on Life

When faced with environmental stress, the immortal jellyfish (Turritopsis dohrnii) reverts from its sexually mature, solitary state to the colonial form from which it originated. Eventually, that colony produces buds and releases free-swimming, solitary, jelly clones—each of which are genetically identical to the jelly that spawned them. This process, which can happen over and over, confers on this tiny animal a type of immortality. 

immortal jellyfish (Turritopsis dohrnii) polyp
In response to physical damage or starvation immortal jellyfish take a leap back in their development, transforming back into a polyp. 
Takashi Murai/The New York Times Syndicate/Redux

Life at the Limits will introduce these and other incredible specializations that let species large and small live to fight another day.