7 Largest Living Sea Creatures

The ocean contains some of the largest creatures on Earth. Here you can meet some of the largest living sea creatures. Some have fierce reputations while others are enormous, gentle giants.

Each marine phylum has its own largest creatures, but this slide show contains some of the largest creatures overall, based on maximum recorded measurements of each species.

1. Blue Whale

It is not only the largest creature in the ocean, it’s the largest creature on Earth. The largest blue whale ever measured was 110 feet long. Their average length is about 70-90 feet.

Just to give you a better perspective, a large blue whale is about the same length as a Boeing 737 airplane, and its tongue alone weighs about 4 tons (about 8,000 pounds, or about the weight of an African elephant).

2.Fin Whale

The second-largest sea creature – and second-largest creature on Earth – is the fin whale. Fin whales are a very slender, graceful whale species.  Fin whales can reach lengths up to 88 feet and weigh up to 80 tons.

These animals have been nicknamed “the greyhounds of the sea” because of their fast swimming speed, which is up to 23 mph.

3.Whale Shark

The trophy for world’s biggest fish isn’t exactly a “trophy fish”… but it’s a big one. It’s the whale shark. The whale shark’s name comes from its size, rather than any characteristics resembling a whale. These fish max out at about 65 feet and can weigh up to 75,000 pounds, making their size rival some of the largest whales on Earth.

Similar to large whales, though, whale sharks eat small creatures.

They filter-feed, by gulping in water, plankton, small fish, and crustaceans and forcing the water through their gills, where their prey gets trapped. During this process, they can filter over 1,500 gallons of water in an hour.

4. Lion’s Mane Jelly

If you include its tentacles, the lion’s mane jelly is one of the longest creatures on Earth. These jellies have 8 groups of tentacles, with 70-150 in each group. Their tentacles are estimated to be able to grow to 120 feet in length.  This is not a web you’d want to get tangled in!  While some jellies are harmless to humans, the lion’s mane jelly can inflict a painful sting.

5.Giant Manta Rays

They are the world’s largest ray species. With their large pectoral fins, they can reach a span of up to 30 feet across, but average-sized manta rays are about 22 feet across.

Giant manta rays feed on zooplankton, and sometimes swim in slow, graceful loops as they consume their prey. The prominent cephalic lobes extending from their head help funnel water and plankton into their mouth.

6.Portuguese Man O’war

It is another animal that is very large based on the size of its tentacles. These animals can be identified by their purplish-blue float, which is only about 6 inches across. But they have long, slender tentacles that can be more than 50 feet long.

Portuguese man o’ wars feed using their tentacles. They have tentacles used to capture the prey, and then stinging tentacles that paralyze the prey.

Although it resembles a jellyfish, the Portuguese man o’ war is actually a siphonophore.

7. Praya Dubia

Giant siphonophores (Praya dubia) can be even longer than a blue whale.  Granted, these aren’t really a single organism, but they bear mentioning in a list of the ocean’s largest creatures.

These fragile, gelatinous animals are cnidarians, which means they are related to corals, sea anemones and jellyfish.  Like corals, siphonophores are colonial organisms, so rather than one whole being (like a blue whale), they are formed by many bodies called zooids.

These organisms are specialized for certain functions like feeding, movement and reproduction – and all strung together on a stem called a stolon so together, they act like one organism.

The Portuguese man o’war is a siphonophore that lives at the ocean surface, but many siphonophores, like the giant siphonophore are pelagic, spending their time floating in the open ocean. These animals can be bioluminescent.

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