Mola mola

Tuna, sailfish, marlin, and many other large marine fish feature long, tapered bodies that glide through the ocean with ease. And then there’s Mola mola, the ocean sunfish — the heaviest of all bony fish. It looks like a giant head with fins at the top and bottom.

Marine biologists have identified four species of ocean sunfish, which inhabit warm and temperate waters around the world. Mola mola is the largest. A typical adult is about six feet long and weighs a ton. And the largest single Mola mola tipped the scales at more than 5,000 pounds.

Not to hurt any fish feelings, but that was two-and-a-half tons of ugly. The Mola mola has no tail fin, so it looks as though something sliced off its back end. It has tall fins on the top and bottom of its truncated body, which it flaps to move itself through the water. And its little round mouth is perpetually open, ready to grab Mola mola’s favorite food, jellyfish.

The fish’s other characteristics aren’t much more appealing than its looks. Its skin is coated with mucus. And Mola mola is often covered with parasites. In fact, it sometimes basks at the surface to allow birds to pick the parasites off its skin.

Mola mola is also prolific. A female can produce up to 300 million eggs at a time — many times more than any other known fish. When they hatch, the tiny larvae are protected by a set of spikes that make them look like multi-pointed stars — a cute phase of life that quickly gives way to the less-attractive adulthood of the ocean sunfish.