When it hatches, a Mola mola is the size of a pinhead but will grow to be the heaviest bony fish in the ocean—and the weirdest.
The weirdness begins with the eggs. A female Mola mola or ocean sunfish produces more eggs than any other vertebrate on earth.
One modest-sized female had an estimate 300 million eggs inside her.
At birth, the baby fish are protected by a star-shaped transparent covering that looks like someone put an alien head inside of a Christmas ornament—albeit a very small only a tenth of an inch across.
Even as a baby, the Mola mola has its parents’ surprised look with the wide eye and open mouth.
The baby will grow fast. Very fast. One individual in the Monterey Bay Aquarium gained 822 pounds in just 15 months (almost 2 pounds a day).
By the time it is an adolescent, the fish will have not tail fin, no ribs, a fused spine, and will swim by flapping its dorsal fin on the top and its anal fin on the bottom.
It will look like a giant swimming head.
Mola molas spend much of their lives in the open ocean chasing the sea jellies (a.k.a. jellyfish) they often eat. They have unusual teeth that are fused together inside a mouth they never close.
They are called the ocean sunfish because they are frequently seen catching rays on the ocean surface. One reason they float on the surface is so birds can peck out the parasites off their skin.
And they have a lot of parasites. More than 50 species of parasites have been recorded on and inside Mola molas.
Like sharks and rays, the female are far bigger than the males. The heaviest Mola mola on record is a female caught in 1996 that weighed 5,071 pounds (2,300 kg).
Here a picture from 1910 of a Mola mola that weighed an estimate 3,500 pounds. (1,600 kg).
The huge decline in shark populations and far greater numbers of sea jellies in the ocean mean Mola molas now have fewer predators and more food. The 21th century looks like a good one if you’re a Mola mola.
But who knows for how long. Given that they are one of the few large fish in the ocean that are doing well, don’t be surprised if someone gives the Mola Mola a catchy new name and starts selling them globally, just as marketers did for the Slimehead (Orange Roughy) and the Patagonia toothfish (Chilean sea bass).
You can see a Mola molas at a Nature Conservancy-supported marine protected area near Bali, Indonesia. The Mola mola congregate near Nusa Penida Island, and during the peak of mola season in October, there is a great chance of seeing the weirdness (and the parasites) of the Mola mola firsthand.