Exotic Animals: The Ocean Sunfish

Every time scientists plunge into the darkest depths of the ocean, they come upon new, startling species. Sometimes only one deep dive can uncover thousands of new species. This adds to the perspective that there are a myriad of wonderful and strange species that lurk in the recesses of the ocean. One such amazing creature is the ocean sunfish, or common mola. Its massive body, weird shape, and peculiar way of movement has shocked onlookers for centuries. Let us learn more about its naming and taxonomy, physical characteristics, and behavior.

In a variety of languages, “sunfish” refers to its shape and sometimes its actions. In English, its name comes from the fact that it has a habit of sunbathing at the surface of the water. However, in many languages, such as Dutch, Portuguese, French, Catalan, and more, its name is “moonfish.” Its strange shape has inspired several unusual names over the course of history. In terms of classification, though it used to be identified as a pufferfish, it is now said to be in its own genus named Mola (Froese, Rainer, and Daniel Pauly).

The appearance of a sunfish continues to astonish people. It does not have back fins per se, but rather a rounded clauvas that acts as a rudder. It has relatively large dorsal fins that are sometimes mistaken for shark fins. Laterally, its body is flattened, and it only has small pectoral fins that resemble fans. The sunfish looks like some part of its body is missing. But what they are not missing is weight and overall size. The largest recorded sunfish was 3.2 meters (10.5 feet) in height. However, the average fin-to-fin height of a sunfish is 2.5 meters (8.2 feet). Probably the most impressive physical statistic of the sunfish is its weight: one specimen was found to be 2,300 kilograms (5,100 pounds) (Rowan, Juliet). Its bone structure is unique as well, with the shortest spinal column of any fish in relation to its body. Its skeleton is mostly made up of cartilaginous tissues. These tissues are lighter than bone, and thus provide an opportunity for the sunfish to grow to sizes much larger than most bony fish. For some more bony information, its teeth have a beak-like structure, and the sunfish even has pharyngeal teeth in its throat. Apparently, getting eaten by this fish is no joke.

This weird fish is in every temperate and tropical ocean in the world. They can get around well, despite having unusual fins, sometimes traveling up to 26 kilometers (16 miles) in a day at a speed of about 3.2 kilometers (2 miles) per hour. They keep relatively close to the surface, with them going no more than 600 meters (2000 feet) deep. Though they seem kind of slow, they can move rapidly when it comes to avoiding getting attacked and when they want to go on the offensive. Most of their time is spent, in fact, hunting below 200 meters (660 feet). When they do go to the surface, laying horizontally, they are thought to be raising their temperature for a long dive into colder waters (British Marine Life Study Society). And when these creatures hunt, they are looking for jellyfish. That is right: not usually our idea of a scrumptious meal. Though most of their diet consists of jellyfish, they like the taste of smaller fishes, fish larvae, squid, and crustaceans (Scientific Reports). Another unusual characteristic of this fish is how many babies the females produce: up to 300 million eggs (Kooijman, S. A. L. M., & Lika, K.). Even more fascinating is that they can grow 60 million times their size from birth. There are still some mysteries about this fish. Scientists are not aware of how long they can live in the wild, though they commonly live up to 10 years in captivity. Also, the mating practices of sunfish are not entirely understood. In addition, without it having a swim bladder, scientists only guess how it stays afloat.

The sunfish is a sight to behold as a giant, flattened fish without tail fins, and it is equally fascinating within with its rare bone structure, teeth, and capacity to reproduce at extraordinary rates. Though it is massive, it does not provide any harm towards divers and aids us in keeping the jellyfish population at bay, no pun intended. Sunfish (or “moonfish” if you are talking about them in Dutch, for example) is one of the wonders of the world, and its threatened status should be reversed, especially with its capacity to give birth to 300 millions babies.

References

Froese, Rainer, and Daniel Pauly, eds. (2007). Species of Mola in FishBase. June 2007 version.

Rowan, Juliet (November 24, 2006). “Tropical sunfish visitor as big as a car.” The New Zealand Herald. Retrieved 2007-05-08.

Ocean Sunfish, Glaucus, British Marine Life Study Society.

Scientific Reports volume 6, Article number: 28762 (2016) doi:10.1038/srep28762.

Kooijman, S. A. L. M., & Lika, K. (2013). Resource allocation to reproduction in animals. Am. Nat. subm, 2(06).

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