Discover the Charming Sea Slug Resembling a Tiny Underwater Algae Tree

Most people aren’t fans of slugs until they encounter a “leaf sheep,” and this cartoonish sea slug is too cute to be real!

These amazingly tiny creatures, measuring just 0.2 to 0.4 inches in length, can be found along the coasts of Japan, Indonesia, and the Philippines. They have faces that bear a remarkable resemblance to cartoon sheep, earning them the nicknames “leaf sheep” or “leaf slugs.”

Take a closer look at one of these enchanting critters, and you’ll notice a pair of dark beady eyes and two rhinophores (antennae-like scent and taste receptors) that together give them a distinctly sheep-like appearance. Combined with a coat of leaf-like plumage known as cerata, it’s no wonder admirers prefer “leaf sheep” to their less catchy official name, Costasiella kuroshimae.

These creatures are more than just their cute faces; leaf slugs possess the clever ability to sustain themselves through photosynthesis. After munching on algae, which is the leaf sheep’s equivalent of grass, they can retain chloroplasts, plant cell organelles that convert light energy into chemical energy.

This means that when sunlight hits these tiny slugs, energy is released into their cells to sustain them. The process of extracting chloroplasts from the algae is called kleptoplasty, and it’s what makes them glow magically, like miniature marine glow-worms.

These fascinating creatures with their bioluminescent, speckled green cerata were first discovered in 1993 off the coast of the Japanese island of Kuroshima, according to the Global Biodiversity Information Facility. They are prevalent throughout the Indo-Pacific, where divers commonly refer to them as the “Shaun the Sheep” of the ocean.

Sharing a mesmerizing photo of one on Facebook, the scuba diving and travel blog My Mola wrote that the leaf sheep sea slug they spotted during their dive near the shore of Zamboanga in the Philippines was “about the size of a grain of rice.”

No matter what category they fall into, there’s no denying the charming – and bizarre – appeal of the leaf sheep. They have earned a small cult following on Instagram, and fans also enjoy watching videos of the relatively newly discovered species on YouTube.

Due to their Japanese origins, nature, and animal blogger Kristen Stanton says many people liken these special “solar-powered sea slugs” to Pokémon. Meanwhile, other observers liken the cerata of these beautifully glowing little critters to the leaves of the succulent aloe vera plant.