DESCRIPTION of SPECIES

Kingdom: Animalia

Phylum: Chordata

Subphylum: Vertebrata

Class: Osteichthyses (the bony fishes)

Order:Tetraodoniformes (trigger fish, boxfish, porcupine fish, puffers)

Family: Molidae

Genus, Species: Mola mola, Masturus lanceolatus, Ranzania laevis

Presently, three distinct species are recognized within the family Molidae including: the common mola, Mola mola Linnaeus 1758, the sharp-tailed mola, Masturus lanceolatus Lienard 1840, and the slender mola, Ranzania laevis Pennant 1776. (Our on-going genetic work may increase that number, so stay tuned!)

Throughout the world, a number of other intriguing common names exist for ocean sunfishes including:

• Poisson lune (France) (meaning "moon fish")
• Schwimmender kopf (German) (meaning "swimming head")
• Putol (Philippines) (Bisaya dialect for "cut short")
• Manbo (Japan)
• Toppled car fish (Taiwan)
• Bezador (Spain)
• Makua (Hawaii)

EARLY LIFE HISTORY

Molas produce an impressive number of eggs. A 1.4m (4.5 ft) female was estimated to be carrying 300 million eggs in her single ovary. (Larger Mola mola would most likely carry even more.) 300 million is several orders of magnitude greater than most other fishes and to date remains the largest number of eggs ever recorded in a single vertebrate as any one time (Carwardine, 1995). Needless to say, the eggs are tiny and would fit into the size of this "o".

After hatching, the larvae expose their affinity to their spiky puffer fish relatives by looking more like swimming pincushions than wee molas. As they grow the spines disappear, as do their tails.

Masturus lanceolatus larvae

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 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 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.

DIET

Mola mola eat a variety of foods, the most common prey items being gelatinous zooplankton like jellyfish, Portuguese man-o-war, ctenophores and salps. Squid, sponges, serpent star bits, eel grass, crustaceans, small fishes and deepwater eel larvae have also been found in M. mola guts indicating that they forage both at the surface, among floating weeds, on the seafloor and into deep water (Norman and Fraser, 1949).

The diet preferences of Masturus lanceolatus are presumed similar to that of Mola mola. Bottom dwelling sponges and annelids have been found in the stomachs of these youngsters (Yabe, 1953).

Ranzania eat an assortment of crustacean, fish and molluscs including myctophid larva, hyperiid amphipods, crab megalops, crab zoea and pteropods. Most feeding appears to take place within 150m (500 ft) of the surface. (Fitch, 1969)

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)

juvenile Mola mola

SIZE, GROWTH and AGE

The average size of an adult Mola mola is 1.8 m (6ft) from snout tip to the end of the "tail" fin and 2.4 m (7 ft 10 in) between the tips of the dorsal and anal fins. The average weight is up to 1 tonne (2200 lbs).

The largest mola ever recorded was 2235 kg (4,927 lbs). It measured 3.1 m (10 ft) from tip to "tail" fin and 4.26 m (14 ft) from dorsal fin to anal fin tip. This animal was a Mola mola and was struck by a boat off Sydney, New South Wales, Australia in September, 1908 (Carwardine, 1995). But see: http://news.nationalgeographic.com
/news/2003/05/0513_030513_sunfish.html.

No data exist on how fast mola grow in the wild but one individual in captivity at the Monterey Bay Aquarium gained 364 kg (800 lbs) in 14 months. Fattened up on a diet of squid, fish and prawns, this fish had to be airlifted out by helicopter and released into the bay after outgrowing its tank.

The longevity of molas in the wild is also a mystery although Kamogawa SeaWorld in Japan has housed the same individual for over 10 years in captivity. We are presently looking into ways of aging molas through a variety of methods.

COLORATION

Mola come in a variety of gray and white patterns with some sporting your basic gray motif while others go for the more polka-dotted appaloosa style. Many also have a slight iridescent sheen. Certain geographic areas may have discrete color patterns—for example the mola in Bali are typically darker than the ones off Southern California but these data are still preliminary.

Mola are capable of color changes particularly when stressed or under attack from a sea lion or other predator and can turn from light to dark within a matter of moments.

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.

Parasitic copepod (Pennella filosa)

PARASITES

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.