Leaf Slug: The Only Animal That Can Photosynthesize

3 mins read

The natural world never ceases to amaze us, thanks in no small part to constant discoveries. Take the division of animal, mineral, and vegetable, for example. For years, most people were willing to believe that organisms – living or otherwise – would fit neatly into one of these definitions.

That would be true, were it not for the existence of Costasiella kuroshimae – known colloquially as the leaf slug, leaf sheep, or our personal favorite, the salty ocean caterpillar. The first nickname is technically the most accurate, as this underwater critter is officially a sea slug. You’ll find the creatures in the oceans of Asia, most notably around Japan, Indonesia, and the Philippines, feasting on green algae.

So, what makes Costasiella kuroshimae worthy of special attention, beyond the fact that they are undeniably adorable on the eye? Well, firstly, they’re the only animal in the world that practices photosynthesis, commonly believed exclusive to plants. Any underwater explorer would be forgiven for assuming that a leaf slug was a small plant. The creature boasts bright green plumage that closely resembles leaves.

So, that explains why these animals are known as leaf slugs – but why leaf sheep? A closer look will reveal all. The creature’s head contains two shaped antennae that resemble the ears of a sheep. These do not play any part in hearing, though. Instead, they pick up on vibrations and scents and help the slug find snacks in the depths of the ocean.

The remarkable photosynthesis process stems from the feeding and basking patterns of the leaf slug. Despite sticking firmly to the bottom of the ocean (mainly for safety – these critters typically max out in size at 5mm), these animals rely upon the sun for energy.

When the slugs eat algae, they absorb chloroplasts from within. These chloroplasts are converted into energy when they react with the sun’s rays. Officially, this is known as kleptoplasty, but it’s essentially photosynthesis – making the leaf slug utterly unique in the animal kingdom.

You can watch the leaf slug in action in this video:

Costasiella kuroshimae looks like a cartoon character that would dwell in Bikini Bottom with SpongeBob SquarePants and his pals, but they’re very real. However, adorable as they are, do not be tempted to look for a pet leaf slug. These animals should be left where they are, living their best life basking in the sun.

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