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The world’s most underrated marine creatures

We shine a light on some of the lesser-known critters critical to the health of our planet. Marine biologist and National Geographic Explorer Diva Amon bigs up her five most unsung denizens of the deep…

01/03/2022Fact-checked 05/10/2022

Translucent ‘phantom’ anglerfish use bioluminescence to attract smaller fish as prey (SPL)


Where do they live? The Atlantic and Antarctic oceans
Why are they underrated? This deep-sea dweller is a personal favourite because the females are trailblazing feminists! Finding a mate in the vast, dark ocean depths can be difficult, so some female anglerfish sport a glowing lure to signal to males. Males, which can be up to 60 times smaller, use huge eyes and nostrils to secure a significant other. When successful, males are so taken with the females’ amazing scent, overwhelming charisma and incredible looks that they bite them. This triggers a reaction that causes the male’s lips to fuse to the female’s side, his organs to dissolve and their circulatory systems to fuse together. Eventually, the male becomes nothing more than the female’s dangling testes, alleviating the problem of finding a mate every time she is ready to reproduce. How anglerfish do this could provide great insights into new kinds of treatments for human transplant patients.

An Atlantic horseshoe crab skims the shallows (Adobe Stock)

Horseshoe crabs

Where do they live? North America and Asia
Why are they underrated? These weird-looking crustaceans aren’t actually crabs but are more closely related to spiders and other arachnids. The living fossils have been roaming the shallows for nearly 450 million years, but what is truly spectacular about them is their milky-blue blood, which has helped to save millions of lives. Horseshoe crab blood has crazy bacteria-sensing capabilities so is used to test for contamination during the manufacture of anything that might go inside the human body, from shots to IV drips and implanted medical devices. The biomedical industry is so reliant on this blood that the disappearance of this species would instantly cripple it.

Oysters fresh from the sea (Adobe Stock)


Where do they live? Shallow salt and brackish water around the world
Why are they underrated? Besides being a delicious source of food for many, oysters are ecosystem engineers. These molluscs, found attached to intertidal hard structures, can have big impacts. They create their own reefs increasing the 3D habitat of the seafloor up to 50-fold, providing homes for other small marine creatures and acting as natural storm barriers. They’re also part of the ocean clean-up crew. They filter water as they eat – up to 50 gallons of water per day for an adult – which helps clean the water and remove certain pollutants. These superpowers have led oyster restoration to become a key activity for getting the ocean back to what it once was.

Electronic microscope image of a dinoflagellate. Opening picture: light micrograph image of dinoflagellates (SPL)


Where do they live? Salt and freshwater, including in snow and ice, around the world
Why are they underrated? Dinoflagellates help to keep us alive! These microscopic plankton live in the upper parts of the world’s ocean where they use sunlight to produce lots of oxygen, which we breathe. And they don’t stop there. Occasionally they are found in such high concentrations that they form harmful blooms causing the water to become discoloured. These red tides can produce toxic effects on people, fish, shellfish, marine mammals and birds. But it’s not all bad news – they also create their own light. When startled, dinoflagellates can turn the surface of the ocean into a beautiful blue-green sparkling scene using bioluminescence. Tiny but mighty!

Light micrograph of a freshwater cyclopoid copepod with two egg sacks (SPL)


Where do they live? Salt and freshwater around the world
Why are they underrated? These tiny crustaceans are the living embodiment of the saying that good things come in small packages. Copepods are a key component of zooplankton and are found in nearly every ocean habitat. They are not only the world’s biggest commuters – and food for the largest animals on the planet – but they also act as a transport vehicle for gigatons of carbon from the shallows to deep-ocean basins. By eating carbon in the form of plankton in the surface waters and then pooping or dying, then drifting into the depths of the ocean, copepods provide an important avenue for carbon sequestration and limiting the pace of climate change. 

Welcome to Earth, a Disney+ original series from National Geographic, is available to watch now

Think you know your dinoflagellates from your copepods?