This week’s featured species is one of the most elusive and least understood species on the planet: the Megamouth shark (Megachasma pelagios). Since it’s discovery, some reports suggest up to 122 megamouth sharks have been observed, but it is difficult to say for certain due to low reporting accuracy from many Asian countries. The megamouth shark is known for its stout body with its soft, loose skin, its wide, blunt head with bulging eyes, its wide paddle-like pectoral fins, and of course its wide mega-sized mouth (Parker, 2008).
The discovery of the megamouth shark was -arguably- one of the greatest discoveries in shark science of the 20th century. In 1976, the U.S. Navy accidentally ensnared the large 14.7 foot (4.5 m), 1,650 lbs (750 kg) shark. Upon examination by ichthyologist Dr. Leighton Taylor, of the Waikiki Aquarium in Hawaii, it was found to be an entirely unknown species of an entirely unknown family. A new family of sharks and a new genus had to be created in order to describe this new find! Almost unheard of in describing of a new shark species (Skomal, 2016). So the new shark was dubbed the Megachasma pelagios – Greek for a shark of “open ocean with a huge mouth” – the Megamouth Shark (Parker, 2008).
Reaching over 18 feet (5.5 m) and 2,650 lbs (1,202 kg), it’s a wonder that the megamouth shark stayed hidden for so long! So why did it take us until 1976 to discover this massive shark? And how have they stayed so elusive since their discovery? There are several elements of the megamouth’s lifestyle that potentially contribute to its elusiveness. First of all, the megamouth shark is one of the three known species of filter feeder. This makes the megamouth shark very unlikely to approach a fishermen’s baited hook and become accidentally entangled (Skomal, 2016). And unlike the other two species of filter feeder sharks, the whale shark and the basking shark which are observed feeding on plankton near the surface, the megamouth has been observed vertically migrating through the water column to follow their prey, epipelagic and mesopelagic euphausiid shrimp, copepods and jellyfish (Yano, Morissey, Yabumoto, & Nakaya, 1997; Compagno, 2001). These vertical migrations mean the megamouth shark travels from depths of 650 feet (198 m) or more during the day up to the shallows at night to feed.
Y Silverio [Videographer]. (2017 July 25). Diver Spots Rare Megamouth Shark Off Indonesia’s Komodo Island [Video Clip]. Retrieved from https://www.youtube.com/
The megamouth shark also feeds using a different methodology than the whale or basking sharks. In fact, its feeding style is more similar to that of a baleen whale than to other filter feeding sharks. The megamouth shark swims towards its food with its mouth wide open, allowing the water to flow into its massive mouth. The water pressure fills and stretches its throat like a balloon. By closing its mouth, the megamouth shark traps its prey inside its expanded throat. Then it squeezes down on its throat. Its prey is swallowed, and the excess water is expelled through its gills (Skomal, 2016). Inside the lining of its mouth, the megamouth shark has a reflective, silvery layer that may be used to attract its prey items (Parker, 2008). It is highly debated as to whether this layer may be bio-luminescent, creating an attractive, eerie glow that its prey cannot resist (Parker, 2008)!
Discovery (2013 August 9). Alien Sharks: The Megamouth [Video Clip]. Retrieved from https://www.youtube.com/
Authority: Taylor, Compagno, & Struhsaker, 1983
Family: Megachasmidae, 1 species
Length: Maximum length may reach greater than 18 feet (5.5 m)
Weight: Up to 2,650 lbs (1,202 kg)
Habitat: Continental and island shelves and slopes, coastal and oceanic waters
Depth: Probably more than 650 feet (198 m) by day, migrating vertically to shallow waters at night
Reproduction: Ovoviviparous; largely unknown
Litter Range: Unknown
Home Range: Worldwide in tropics to cool temperate waters
Diet: Filter feeder; small copepods, microscopic/planktonic animals, small shrimps
IUCN Status: Least Concern; population status is unknown; rarely encountered species
(Parker, 2008; Simpfendorfer, & Compagno, 2015; Skomal, 2016)
Thanks for checking out one of the most elusive shark species this week! It’s amazing to think what other treasures the ocean may still hold that we don’t know about! -Just don’t get your hopes up about Megalodon still being out there; they are well and truly gone friends! If you missed last week’s featured species, be sure to hop back and check out the Eastern Angel Shark.
The new Ocean For Sharks Shop is open! There’s handmade ocean inspired plush animals, canvas paintings, and of course my children’s book, Winifred the Wondrous Whale Shark, available in print and PDF. Be sure to stop by. Remember proceeds benefit shark research and conservation with a donation to Project AWARE!
Remember you can make a difference for marine ecosystems by calling your Congress man or woman and tell them that you care about the quality of our waters! Sharks, rays, and other marine organisms cannot speak or be represented in Congress. They need your voice. Get involved and stand up for sharks. Until next time finatics.
Featured Image Source
Rasner, B. (Photographer). (n.d.). Megamouth in Dana Pt California [Digital Image]. Retrieved from https://cdn-images-1.medium.com/max/2000/1*xpMXH5OdIlPzGRzwvtF7Gw.jpeg
Compagno, L. J. (2001). Sharks of the world: an annotated and illustrated catalogue of shark species known to date (Vol. 1). Food & Agriculture Org..
Gibbens, S. (2017, July 27). Rare Megamouth Shark Captured on Video. Retrieved January 02, 2018, from https://news.nationalgeographic.com/2017/07/rare-megamouth-shark-sighting-video-spd/
Parker, S. (2008). The encyclopedia of sharks (2nd ed.). Buffalo, NY: Firefly Books Ltd.
Simpfendorfer, C. & Compagno, L.J.V. (2015). Megachasma pelagios. The IUCN Red List of Threatened Species 2015: e.T39338A2900476.
Skomal, G. (2016). The Shark Handbook: The Essential Guide for Understanding the Sharks of the World. (2nd ed.). Kennebunkport, ME: Cider Mill Press.
Tricas, T. C., Deacon, K., Last, P., McCosker, J. E., Walker, T. I., & Taylor, L. (1997). The Nature Company Guides: Sharks and Rays. (L. Taylor, Ed.). Hong Kong: The Nature Company, Time Life Books.
Yano, K., Morissey, J.F., Yabumoto, Y. and Nakaya, K. 1997. Biology of the Megamouth Shark. Tokai University Press, Tokyo, Japan.