Mola mola (Roundtailed or Common mola)

The most common of the ocean sunfishes is the Mola mola. These fish, like all sunfishes, appear as if their bodies have been somehow truncated leaving them little more than a large head equipped with long sweeping fins atop and below. The body is less than twice as long as it is deep.

Mola mola have a rounded tail, gritty sandpapery skin covered with copious amounts of mucus. Typically silvery in color with a slight opalescent sheen, they can exhibit strikingly changeable spotty patterns. They presently hold the record for the world’s heaviest bony fish--a 3.1 meter (10 ft) long specimen weighed in at 2235 kg (4927 lbs) (Carwardine, 1995).

Masturus lanceolatus (Sharp-tailed mola)

Masturus can also reach great sizes. As their common name implies, sharp-tailed mola have a bit more to their tail than Mola mola. Similarly colored to Mola mola, they have a much smoother skin and produce less mucus. Interestingly, sharp-tailed molas are not consummate sunbathers and carry a smaller parasite load.

Ranzania laevis (Slender mola)

Unlike other molas, the slender mola never reaches more than a couple of feet in length. These are the most colorful and rarest of the ocean sunfishes. They have a smooth and thinner skin and a vertically oriented mouth.

The Polynesians called these sunfish "King of the Mackerels". It was seen as bad luck to catch and kill Ranzania for such an act would render the mackerel incapable of finding their way to the islands.

A NOTE ABOUT NAMES

The common name "sunfish" is used to describe the marine family, Molidae, as well as the freshwater family, Centrarchidae. The common names "ocean sunfish" and "mola" refer only to the family Molidae and can be applied all three Molidae species.

The word mola comes from Latin and means millstone–in reference to these fishes’ roundish shape. The common name "ocean sunfish" comes from the Mola mola’s habit of lying atop the surface of the ocean appearing to sunbathe.

DISTRIBUTION

All three species of sunfish are found in all tropical and temperate oceans. With insight gleaned from our incoming satellite tagging data and our internet sighting form, we are beginning to outline the seasonal distribution of ocean sunfishes throughout the world’s oceans. And some interesting patterns are beginning to emerge.

Lepeoptheirus sp. or Caligus sp .
Click for detail. Can you count them all? Photo courtesty Chris Potgieter
Sept 30,2007 at Crystal Bay, Lebongang, Bali Dive depth was 45m at the cleaning station.

Parasitic copepod (Pennella filosa)

Didymozoid trematode
Removed from the inside of a Masturus lanceolatus in Hua Lien Taiwan--supposedly 1 in 100 Masturus there have these tumors.

Since parasites often sport multiple hosts, they can offer valuable insight into mola interspecies associations. For instance, one mola parasite is the larval stage of a shark tapeworm so at some point the mola most likely falls prey to shark enabling this parasite to complete its lifecycle. For a list of known parasites of the family Molidae click here

The common sunfish, Mola mola, are infamous for their impressive parasite load. Some 40 different genera of parasites have been recorded on this species alone. In fact, even their parasites have parasites–a fact reminiscent of Jonathan Swift’s quip:

So, naturalists observe, a flea

Has smaller fleas that on him prey;

And these have smaller still to bite ’em;

And so proceed ad infinitum

Masturus lanceolatus are not as heavily parasitized as Mola mola. And while they dive to great depths, even greater than those of the Mola mola, they do not appear to engage in sunbathing to the same degree. Little is known about the parasites of Ranzania, the slender mola.

Mola skin 88x

Mola scales 176x

Sea lions (Zalophus californianus)

Bat stars (Asterina miniata) consuming dead sunfish

PREDATORS

There's safety in great size for the ocean sunfishes but on the road to largess, they are open to many dangers. Bycatch through fishing certainly takes a toll on mola populations. And parasites presumably claim quite a few lives as well. Other predators include orcas (Gladstone, 1988) and sea lions.

During the fall months in Monterey, California, sea lions can be seen ripping the fins off sunfish and slamming the dismembered bodies against the sea surface. Presumably this action helps the lions tear through the molas’ skin which is leathery tough and several centimeters thick in places. However, after tossing the bodies through the air for several minutes, the lions often simply abandon their prey. Tragically the hapless, finless molas unceremoniously sink to the seafloor and are consumed slowly by bat stars.

Little is known about predation on Ranzania. However an adult female (335 mm in total length) was found in the stomach of a marlin off Hawaii. Numerous Ranzania youngsters have also been found in the guts of mahi mahi Coryphaena hippurus. (Sherman, 1961)