A tiny, neon-green sea slug known as the “leaf sheep” has been crowned the winner of the 2026 Invertebrate of the Year competition. The creature, scientifically named Costasiella kuroshimae, secured the title following a global ballot that saw hundreds of thousands of participants celebrate the diverse world of spineless animals.
Broadcaster and environmental campaigner Chris Packham announced the results, praising the slug’s unique biology. “It’s very, very beautiful but also very smart too,” Packham said. “It harvests photosynthetic material from the algae it feeds upon and builds its own solar panels.”
This year’s contest was notably competitive. The leaf sheep, which inhabits tropical waters near Japan, the Philippines, and Indonesia, narrowly defeated the world’s largest bumblebee, the Bombus dahlbomii. Known as the moscardón, this giant ginger bee is currently facing threats in its native Patagonia due to the introduction of invasive species. The horseshoe crab, a prehistoric arthropod with blue blood, took third place, followed by the common woodlouse. The bootlace worm, recognized as one of the longest animals on the planet, rounded out the top 10 list.
The competition was established three years ago to highlight the importance of invertebrates, which account for approximately 97% of all animal species—totaling at least 1.7 million known varieties, with many more awaiting scientific discovery. These creatures perform essential ecological roles, including waste recycling, water filtration, soil fertilization, and crop pollination, all of which are vital to human survival.
The selection process began with several thousand nominations from the public, ranging from children to professional scientists, which were eventually narrowed down to a final shortlist of 10. Throughout the two-week voting period, experts shared insights on various species, with figures like Erica McAlister discussing the importance of flies, photographer Dara Ojo highlighting macro photography, and Connor Butler emphasizing the interconnectedness of all living systems.
First described by science in 1993, the leaf sheep has gained significant popularity in recent years through macro photography, which showcases its charming, cartoon-like appearance. Its unique look has even served as inspiration for at least one character in the Pokémon franchise, cementing its status as a favorite among nature enthusiasts. The report also notes that who number at least 1.7m species – about 97% of all animals – with probably millions more still to be discovered and d, the competition was launched three years ago to celebrate overlooked and often derided invertebrates. The report also notes that see the top 10 shortlist here. The report also notes that charming leaf sheep fought off strong competition from the world’s largest bumblebee, the moscardón, Bombus dahlbomii, which finished second, in a much closer contest than previous years – when the tardigrade and the common earthworm won with popular landslides – the beady-eyed. The report also notes that filter water, recycle waste, clean up pollution and add fertility to soils, human life on Earth would quickly perish, without the unpaid labour of wild invertebrates who pollinate crucial crops.
