Masters Of Marine Disguise

Throughout the oceans, many animals are on a mission to avoid their predators, while others hope to hide from their prey. One of the best ways to do so is to blend into the background. And there's no shortage of species that can slip out of sight simply because they are superbly matched to their surroundings. This week, Alexis, Jess and I are sharing some of our favourite masters of disguise, with a sprinkling of how and why they do it.

Seahorses fall into the category of animals that stay out of sight not to be nommed. The pygmy seahorse is a mere two centimetres tall and is peppered with bulbous blobs known as tubercles, which resemble the coral polyps amongst which it lives. There are all sorts of species, each suited to their setting. Many pygmy seahorses sit amongst sea fans, using their tiny tail to cling to the coral. This puts them in a great position to feed far from the sight of potential predators. In fact, these wee ones are so well camouflaged that they weren't even discovered until scientists were scrutinising samples of coral brought to the lab. Whether pygmy seahorses can change colour according to their accommodation (a yellow sea fan or a red one, for example) is unknown, but some can change colour according to their surroundings.

Like the pygmy seahorse, leafy sea dragons (Phycodurus eques) can casually blend into their environment, tall forests of kelp held aloft by tough green floats. Their disguise comes at a price, though - compare an enthusiastic marathon runner raising money for the Shark Trust and dressed to match - such a great costume is hard to manoeuvre; their streamlined lycra-clad companions are a lot more lithe. Their pectoral fins are their only propellers and - as they hover between the towering algal fronds - they hoover up plankton and small crustaceans with their pipe-like snouts.

On the terrifying end of things, some venomous marine creatures like stonefish and scorpionfish enjoy hiding amongst their habitat disguised as rocks. The aim is to to attack unsuspecting prey items that swim past a seemingly inoccuous rock, while the venom they deploy from sharp spines hidden in the dorsal fins protects them from becoming prey items to larger creatures. Unfortunately for us humans, stepping upon a stonefish can be either simply extremely painful, or fatal. While the tassled wobbegong isn't venomous, it also sits on and blends into the seafloor, waiting to swallow prey (including other sharks), and has been known to attack humans when provoked. Just a few more reasons not to tread upon marine life when out enjoying the ocean.

Instead of relying on special skin patterns or body shapes, decorator urchins blend in by picking up bits of rock, coral, and algae with their little urchin arms and holding these items up like a disguise.

Hatchetfish are deep-sea pelagic fishes, meaning they don't live near the ocean bottom or near the shore. Unlike most of the other animals we've talked about, they blend into isn't patterned seafloor, seaweed, or coral or - it's liquid blue darkness. Hachetfish hide themselves by being mirrors of their environment - literally! Their scales on their mirror-like sides always are a perfect reflection of the exact color of dark blue that they happen to be swimming in. This reflection works really to hide them from predators that are looking from them from the same level in the water, but it doesn't work so well from the side, where the light shining down from above can create a give-away shadow. To blend into the light from above, hatchetfish have bioluminescent bellies that light up to the same color of blue.

Update (26/02/14): video of BBC footage updated to include original narration.

By Alexis, Jess and Sara

Images

1) Pygmy seahorse (Hippocampus bargibanti). Credit: Steve Childs via Flickr

2) Leafy sea dragon (Phycodurus eques). Credit: Ta-graphy via Wikimedia Commons

3) Stonefish. Credit: Alan Slater via Wikipedia Commons.

4) Tassled wobbegong (Orectolobus dasypogon). Credit: Jon Hanson via Flickr