The ocean sunfish, called Mola mola, can weigh up to 2,000 kilograms. It has a huge round body and no tail.

It moves slowly and has a very large surface area. The fish also travels long distances, moving up and down through different water layers many times each day.

Because it is slow and its body is big, many parasites can attach to it. Parasites are found on its skin, gills, fins, eyeballs, mouth and intestine.

Sarika Cullis‑Suzuki, host of The Nature of Things 101, says, “This fish has parasites everywhere.” Scientists have identified 73 different parasite species on the Mola mola and other ocean sunfish.

The fish’s size, shape and slow, wide‑ranging movements make it especially vulnerable to many parasites.