Today’s Wonder of the Day was inspired by Isabella. Isabella Wonders, “What is a Mola Mola Sunfish?” Thanks for WONDERing with us, Isabella!

What's your favorite thing to do when you go to the beach? Soak up some rays while you read a good book? Build a sand castle that rivals the biggest skyscrapers? Or is your first priority to hit the water and dive beneath the warm, salty waves?

If you love to swim, there's no place quite like the ocean. Of course, you do have to be careful. When you swim in the ocean, you're entering the home of a wide variety of sea creatures, not all of whom want you there!

For example, if you're swimming amongst the waves and glance over your shoulder, there's one thing you probably don't want to see: a dorsal fin. Although other fishes have dorsal fins, they're usually associated with sharks, and no one wants to be swimming with sharks!

Depending upon where you're swimming, though, seeing a dorsal fin might not be a bad thing at all. Instead of a shark, it could belong to a curious sea creature that happens to be the heaviest bony fish on Earth: the ocean sunfish, which is also commonly known as the mola or sunfish.

Scientifically known as Mola mola (which is where its common name "mola" comes from), the ocean sunfish tends to make its home in the deep waters of temperate and tropical oceans. Their large, silvery bodies can occasionally be seen near the surface, where they go to soak up the Sun's rays. This is also when their dorsal fins may break the surface, making swimmers think sharks are near.

The largest ocean sunfish can span up to 14 feet vertically and 10 feet horizontally. Even though they're large fish, their appearance is a bit odd, since they often look like only half a fish. Their bullet-like shape develops because their back fin never grows. Instead, as ocean sunfish grow, the back fin folds in on itself, creating a rounded, rudder-like appendage called a clavus.

Adult ocean sunfish weigh an average of 500-2,000 pounds. However, the largest examples of the species can weigh over 5,000 pounds! Some sharks and rays can weigh even more, but they're considered cartilaginous rather than bony fish.

Despite their large size, ocean sunfish have fairly small mouths. Their primary and favorite food is jellyfish, but they also will eat small fish, plankton, and algae when jellyfish are unavailable.

If you happen to see an ocean sunfish, you may notice its rough skin covered with parasites. They're prone to parasite infestations and will sometimes leap out of the water and land flat like a belly flop in an attempt to shake them off. They'll also occasionally stay near the surface to let small fish and birds feast on the parasites.

Ocean sunfish are harmless to humans, but they can be very curious and have been known to approach divers. If you want to see an ocean sunfish, you might need to learn how to SCUBA dive, since they're usually not kept in aquariums in captivity because they're hard to care for.

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