A semiaquatic lizard living in the rainforest of Costa Rica is making quite a splash in the world of reptile science. Anolis aquaticus, or the diving anole, is the first known vertebrae to use bubbles to breathe underwater. Just like a human scuba diver!

Small, slow, and apparently delicious considering the number of predators it attracts, the diving anole relies mainly on camouflage to keep it safe from the birds, snakes, mammals and other lizards eager to make a meal of it. 

But when camouflage fails this anole has another trick up its sleeve. It dives into the nearest stream and waits for its enemy to move along. And thanks to an ingenious ‘bubble hat’ the anole can wait down there a long time.

Fast fact: Anoles have been reported to stay submerged underwater as long as 16 minutes.

While underwater the anole exhales a bubble which clings to its nose rather than rising to the surface.  The lizard then uses the bubble as a source of oxygen, inhaling its air and prolonging the time it can hide on the bottom of the stream. As it breathes the bubble expands and contracts. Scientists have called this method ‘rebreathing’ after the apparatus used in scuba diving. It can also be called ‘plastron respiration.’ The plastron is the name of the thin film of trapped air.

The anole’s scaly skin is covered in tiny spines and even tinier spinules (about 11.2 million of these tiny spines can be found per square millimetre) that make its body hydrophobic, or water repellant. Having skin that can’t get wet means it is self-cleaning, drag is reduced when swimming and its body heat is conserved. It also means the spines can capture and hold onto a thin layer of air next to the skin.

One curiousity still to be explored is where the air in the attached bubbles is coming from. Does the anole carry it down in its lungs or attached to its skin? Or does the air diffuse from the water itself?

Fast fact: Water beetles and diving bell spiders are examples of arachnids and insects that trap air in bubbles to breathe underwater.

One drawback of this clever survival trick is that mountain streams tend to be very cold. As an ectotherm, a creature that regulates its body temperature through its environment, the anole might find this drop in temperature affects it ability to defend itself or even digest food.

There are over 400 different species of anole, in all colours and sizes Most are green, brown, or grey and about 35-85 millimetres in length and weighing between 1-10 grams. Their two primary traits are their large toepads and a flap of skin attached to its throat called a dewlap. 

Anoles give scientists a unique opportunity to watch evolution unfold in a very short period. When a species of stocky brown anole was introduced in the Southern United States the small green anole native to that environment found it could not compete for insects on the ground.  In response it retreated to tree branches above where hunting was not as competitive. Within 20 generations (about 15 years) those green anoles had developed bigger, stickier toe pads to make life in the trees more manageable.