For millennia, people have wondered just how many species live on Earth. The latest study looking to answer this question suggests there are about 8.7 million species, the majority of which scientists can’t even name.
The oceans, as almost three-quarters of the Earth’s surface, are home to millions of species—and only about 1 in 10 has been officially discovered by scientists. Here are ten ocean-dwellers we think are especially fascinating:
1. The box jellyfish, which lives in the waters off North Australia and Indonesia, is one of the most venomous species in the ocean. Its 10-foot-long tentacles can kill even cautious swimmers, yet some kinds of sea turtles can eat box jellyfish without even an upset stomach.
2. The lovely hatchetfish might be redefining lovely, but its thinness when viewed head-on helps it hide from predators, as does its silver color and bioluminescence.
3. Sailor’s eyeball is the oceanic equivalent of skinless grapes at Halloween. This seaweed lives in waters around the equator, where it reproduces by disintegrating once young plants have formed inside of it.
4. The blue-ringed octopus may look pretty, but its vivid colors, which become brighter when the animal is disturbed, mark it as extremely poisonous—it is the most dangerous cephalopod and its saliva can kill a human.
5. The stonefish, the most venomous fish, can also kill a human with one sting. It takes its name from the camouflage that allows it to lie in wait for passing fish.
6. The marine otter, which looks more like a river otter than a sea otter, lives in sea caves just above high tide on the rocky coast of Chile. According to current estimates, there may only be 1000 of these animals, which are hunted for their fur.
7. The peacock mantis shrimp use spring-like joins in their legs and very sophisticated eyes to catch their prey, including animals larger than themselves and animals with protective shells.
8. The female hairy angler, named for its sensory hairs, uses a lure attached to its forehead to trap prey in deep, dark ocean waters. Males are much smaller and lack this lure, so live as parasites on their mates.
9. The yellow-bellied sea snake is rare in that it lives near the surface of the open ocean, where it often swims in a group of thousands. It is also highly poisonous, with venom more toxic than a cobra’s.
10. The bubble shell, which lives in the Indian and western Pacific Oceans, feeds on sedentary worms and vomits when threatened. It is named for its red-patterned translucent shell, which protects the body outlined in fluorescent blue.
You can learn about these and many other fascinating ocean creatures in our marine life encyclopedia. What's your favorite?