Megamouth sharks (Megachasma pelagios) are species of deepwater sharks that rarely have an encounter with humans after their discovery in 1976. This Shark is one of the three extant filter-feeding sharks (others include the whale shark and the basking shark) discovered off Hawaii coast entangled with the sea anchor of the united states navy ship.
On discovery, scientists could not immediately classify this sea creature because of its strange and mystic appearance. To solve this classification issue, they created an entirely new genus Megachasma and family Megachasmidae for the species. Megamouth sharks have a worldwide distribution in all the tropical areas of the world.
Kingdom – Animalia
Phylum – Chordata
Class – Chondrichthyes
Order – Lamniform
Family – Megachasmidae
Genus – Megachasma
Species – M. pelagios
Description of the Megamouth Shark
Apart from the weird appearance of megamouth sharks, only a little information is available about them. They have a brownish-black color on top of their body and a white color underneath with an asymmetrical tail that has a long upper lobe, like that of thresher shark. Their gill slits interior have gill rakers lining it, used to filter in their foods.
Megamouth sharks are relatively weak swimmers, and they have a soft, limp body, with no caudal keels. Among the filter-feeding sharks, megamouth is the less active species. They have a bulbous and flattened head. Also, their distinctive feature, which is their mouth holds an enormous tongue, covered with small but sharp teeth that secrets mucus. There is an elongated nostril, situated above the prominent lips.
From the word “Mega” which means “Huge”, you may have guessed that these sharks have a largemouth. Their mouth contains small teeth, a rounded snout that causes observers sometimes to mistake them for young Orcas. These sharks have protruding upper lips that are silvery-white and very visible when they open their mouth.
Megamouth sharks have tiny eyes and swim in stiff, slow movements. Scientists thought their lips were embedded by “Lambent photophores” when analyzing it in the early 1980s which may entice plankton. Another team of scientists that examined these sharks in the mid-1980s proposed that the lower lip may glow with the white band used as a reflector of some kind. Either way, none of these theories has been proven to be true.
The white band is present in both sexes and could either serve as a means of identifying other megamouth sharks or as a feeding mechanism. They have a mouth that can reach up to 4.25 ft in width.
Megamouth sharks have 50 rows of teeth in their upper jaw and about 75 rows of teeth in their lower jaw. The lower part of megamouth sharks’ snout has a concentration of the ampullae of Lorenzini. This is an electroreceptor that most sharks uses for electrolocation, i.e. detecting weak electrical impulses. This Shark can also detect changes in the salinity of water, temperature and electrical field. They have small gills openings behind their eyes.
These sharks have a dorsal surface that is blackish brown and a white ventral surface. Areas between their eyes and nostrils are paler. They have a lower jaw with silver tint and a lot of dark spots. The ventral side of their head behind the lower jaw is light grey. Megamouth has a silver oral membrane at the roof of the mouth.
The megamouth has about 50 rows of small, numerous teeth on each side of their jaw, but only three rows are functional. Their females have fewer teeth rows than their males. This sharks’ upper and lower jaws meet at the symphyseal. Megamouth first upper teeth are smaller than the primary five lower teeth, the cusps of the lower teeth are more incisive and longer than that of the upper teeth.
Megamouth’s first dorsal fin is blunt, low situated and has the shape of a diamond. Likewise, their second dorsal fin is similar to the first, but a bit smaller and its base is wider. The pectoral fins have rounded tips. Near the anus of this Shark is a small triangular, low situated anal fin. Their tail is big and asymmetrical with the upper part more significant than the lower one.
Megamouth sharks have dermal denticles that differ in size and shape at each region of their body. Also, on their tongues are tiny mucose. They have many pigment cells on their dorsal side but none on their ventral side.
They have a weight of about 2,679 pounds, depending on the individual.
Average Length and Size of Megamouth Shark
There is no data on their range at birth. However, their matured males measure about 13.1 ft and their grown females at approximately16.4 feet. The maximum recorded megamouth has been higher than 18 ft.
What is Megamouth Swimming Speed?
They are relatively slow compare to other filter-feeding sharks, Basking shark, and whale shark.
Scientists only discovered megamouth in 1976 off the coast of Hawaii; however, there is still not enough data about them. Since the first discovery, there have been sightings/capturing of megamouths in Japan, Philippines, and new guineas. They have a worldwide distribution in all the major tropical areas of the world.
One has been found in Brazil, another one off the west coast of Africa (Senegal) and there is another record of one in South Africa, but from the files, it is not as common in Atlantic as it is in the pacific. They also seem to be relatively common in the eastern area of the Indian ocean.
Megamouth sharks live in deep scattering layer of the ocean. They seem to enjoy warmer climates, although the first discovery was in temperate waters.
The first megamouth discovered was on November 15, 1976, about 25 miles off the coast of Hawaii. This individual tangled with the sea anchor of the united states navy ship. It was so strange that the scientist had to create a new family and genus for it.
The examination of the 14.7 ft specimen by Leighton Taylor showed it to be a completely unknown shark, making it one of the sensational discoveries in 20th-century ichthyology together with the Coelacanth. Scientists studied the pectoral fin, along with the skeletal and muscular system of the shark. This was to identify its phylogenetic relationship to the other two sharks (the whale shark and basking shark).
Megamouth sharks are naturally filter feeders. They use their enormous mouth to draw in water and filter out planktonic animals such as krills (especially the family of euphasiidae), shrimps, and lobsters or sometimes jellyfish.
When searching for food, megamouth sharks swim vertically according to how krill move or into groups of small crustaceans opening its mouth full. To feed, it pulls its jaws in and out cyclically, widening its mouth cavity at the same time. Afterward, it pushes out the water from the bubble through the gills to filter in plankton. This way, the filtered food moves to the stomach.
Typical Behaviour of Megamouth Sharks
In 1990, scientists caught a male megamouth shark about 16 feet near the surface off Dana point, California. They later released this Shark back into the water with a small radio tag attached to its body. The tag communicated time and depth information over two days. During this time, the Shark swam at a depth of around 390 – 520 ft (120 – 160m). But during the sunset, this Shark would ascend and spend the nights at depths between 39 and 82 ft (12 and 25 m).
For both night and day, the progress of this Shark was very slow around 0.93 – 1.30 mph. The vertical migration pattern is common in many marine animals as they track the movement of plankton in the water. The megamouth shark captured in March 2009 was reportedly netted at a depth of 660 ft (200 m).
This shark also swims with its mouth wide open like the other two planktivorous sharks, filtering water for jellyfish and plankton. In contrast to many other deepwater sharks, megamouth shows a decrease in specific gravity in the form of slack and a severely calcified cartilaginous skeleton, loose skin, and loose muscles and connective tissue.
The large liver of this shark allows more significant production of liver oil to increase hydrostatic support and specific gravity. Researchers believe megamouth shark to be diurnal, that is, they mostly operate during the daytime. They regularly alternate between deep and shallow waters. Also, there are observations of this species traveling from the Atlantic ocean through to the pacific and Indian oceans. Most behaviors of the megamouth shark are speculations by experts as their preferences remain a mystery.
Predators of Megamouth Sharks
There is only only one specific event of predation on record, and it is with sperm whales (Physeter macrocephalus). It occurred in Manado in Indonesia on August 30, 1998, near midday. While some researchers were observing the whales, the base of megamouth’s gills and dorsal fin showed signs of the sperm whales attack. Sperm whales are considered squid feeders, but there have been cases of small deep-sea sharks in their stomach content which makes it quite confusing.
IUCN assessed the Megachasma pelagios as “Least Concern”. This assessment follows the fact that this shark has a widespread distribution and a generally limited interaction with fisheries. Although like many other marine mammals, there is an increasing threat by fisheries.
They sometimes end up in the bycatch of vessels operating in the waters of south-east Asia. Since the first discovery of this species, less than ten have been studied making the information available on the species very limited.
List of Megamouth Sharks Specimens Known Through History
As of March 2018, less than 100 megamouth shark had been sighted or caught. Scientists found some in the Atlantic, Pacific, and Indian oceans, the Philippines, Japan, and Taiwan. Also, some sighting occurred in waters near California, Hawaii, Indonesia, Mexico, Brazil, Australia, Senegal, and Puerto Rico.
The 2009 Specimen
On March 30, 2009, a megamouth shark of about 400 to 500 kg died while struggling in a fisherman’s net. The fisherman then took it to a nearby Dorsol in Sorsogon province for analyses by scientists before butchering and selling it.
The 2011 Specimen
On June 12, 2011, fishermen found a male megamouth dead near the western Baja California Peninsula. Picked up by the same fishing vessel that captured the 2006 megamouth specimen. The fishermen then took the new specimen to Ensenada for photographing and cut up for the Scripps Institution of oceanography and Mexican researchers to study the structure of its gills and muscles.
On May 7, 2014, Scientists captured a 13 ft ( 4 m), 1,500 Ib (680 kg) female megamouth shark at a depth of 2,600 ft off the coast of Shizuoka, Japan. They analyzed the Shark in front of the public In the marine science museum in Shizuoka city, japan.
On June 30, 2014, another event involved the capturing of a 1,100 Ib female in the shallow waters of Cagayan de Oro in the Philippines. Samples of this individual were then sent to the Bureau of fisheries and aquatic resources in northern Mindanao. The outer skin together with the jaw displayed at the D’ Bone collector museum in Davao.
The 2015 Specimen
On January 28, 2015, a 15 ft (4.5 m) a megalodon was found dead by residents of barangay Marigondon in Pio Duran town, Albay, Philippines. The sample is now on display at the Albay parks and Wildlife, hence, open to public view since March 3, 2015. Also, the preservation process of this specimen involved taxidermy. Now it is one of the most treasured collections of Albay (a leading province in environment protection).
The 2016 Specimen
On April 14, 2016, a 16ft deceased megamouth shark, tangled in a fisherman’s net in Japan’s Mie Prefecture, about three miles off Owase port. The Shark weighed about 2,000 Ib. In August 2016, Scientists cut the shark before an audience of academics and students. Osaka Aquarium in Japan organized the event.
On May 1, 2017, a nearly 9.8 ft megamouth shark washed up at Barangay Baluarte in Misamis oriental, a place in the northern Mindanao of the Philippines. Authorities buried the estimated 1,300 Ib shark to prevent indigenes from consuming it because they weren’t sure of what led to its death.
On May 22, 2017, a fishing net trapped a living megamouth, off Sunosaki lighthouse in Tateyama in Japan. The estimated 16 ft (5 m) to 20 ft (6 m) female was captured on camera by an Asahi Shimbun photographer. Afterward, an examination by a celebrity tv marine biologist that usually calls himself Sakana-Kun or Fish Kid followed. The following day, the shark died.
On July 25, 2017, a diver recorded a megalodon on video in a place called Gili law Laut near Komodo Island in Indonesia as it swam slowly past Heikki Innanen and penny Belich.
The 2018 Specimen
On February 11, 2018, a juvenile male megalodon got caught in a fishing net accidentally in negros oriental, in the Philippines. The body of the dead Shark was buried at barangay Villareal later that afternoon. However, the following day, it was exhumed so scientists could conduct a necropsy to find the cause of death and get tissue samples for further research.
Megamouth Sharks and Humans
Humans consume Megamouth sharks and use their fins.
On the side of the shark, there are no records yet of threats to humans
Scientists do not know much about these sharks’ reproduction. However, they presumed them to be viviparous/ovoviviparous with developing embryos feeding through oophagy. Megamouth sharks are thought to mate through internal fertilization and give birth to live relatively large pups. Although megamouth sharks give birth to their pups, they do not connect to their young ones through a placenta.
During the gestation, the mother probably provides her young ones with unfertilized eggs that they eat for nourishment. Immediately megamouth sharks are born, they instantly become filter feeders. There is evidence that the males try to hold down their females during copulation because one female megamouth was found to have similar lower jaw wounds other mating sharks do have.
A Studied male megamouth shark proved that they have a clasper (an intromittent organ characteristic for cartilaginous fish) near their ventral fins. The female megamouth sharks also have a vaginal tract that connects to their double uterus, formed where their ventral fins meet.
Observations indicate that the breeding period occurs during autumn. Thorough studies of a megamouth caught in japan showed that mating might occur anytime in the year. Males of megamouth sharks are assumed to become sexually mature when they reach a length of 13 ft and females at least 16 ft long.
Scientists took tissue samples from 27 megamouth sharks captured in two years off the Hualien coast and another two caught in Baja California, Mexico to perform a population genetic analysis on them. The results showed no genetic diversity between populations found in separate geographical locations. This indicates that the species form a single, migratory interbreeding population.
RSI (Ram-suction index)
Megamouth sharks are more than likely high on the suction side of the RSI; they suck on plankton to feed. All the same, the three planktivorous sharks have ram feeding as a common thing between them. Therefore it is more than likely that megamouth uses a combination of both. Megamouth feed in a three-step method
1. Vertical Feeding
This involves floating vertically making very little to no forward movement. They use a suction method to draw in their prey.
2. Active Feeding
These sharks use suction-filter feeding while continuously swimming, enabling them to draw water into their mouth at higher speeds. This kind of feeding is also called Ram-filter feeding. They open their mouths, allow water to come in and then their bodies filter-in food while releasing the debris and water back into the ocean.
3. Passive Feeding
Swimming with mouth open to strain plankton from the sea.
Interesting Facts About Megamouth Sharks
1. This Shark Got Its Name from Its Enormous Size.
The name mega is from the Greek meaning “huge”. While the scientific name Megachasma pelagios interprets to Huge (Mega), gaping or yawing (chasma), and sea (pelagios).
2. Megamouth Can Reach Up to 6m Long
The largest recorded megamouth was a carcass found in Taiwan that measured up to 19 feet. Researchers believe that they can be more prominent.
3. Megamouth’s closest relative is “Thresher shark.”
4. They are Planktivorous Engulfment Feeder.
Megamouth is one of the three filter-feeding sharks that includes basking shark and the whale shark. Scientists believed they mainly suck in their krill diet. However, a recent study showed that they perform engulfment feeding, which is typical of baleen whales (the only Shark thought to use this mechanism).
5. Their Highly Luminescent Mouth Might be a Light Trap
Scientists believe that the slow swimming megamouth sharks might use their highly reflective, luminescent mouth as a light trap to attract their prey. They also proposed that a bioluminescent strip above the mouth may be used in either way. Neither of these behaviors has been proven.
6. Preyed on by Whales and Sharks
Recorded predators of megamouth sharks include orcas, sperm whales, and other large sharks.
7. They can detect their food while swimming through the water.
8. Megamouth is a wide-ranging species:
These species occur in the Atlantic, Indian, and Pacific oceans.
9. The Megamouth Shark is not a Great Swimmer
According to the Florida Museum of Natural History. Megamouth is a less active and weaker swimmer than whale sharks or basking. Reduced mobility is a reflection of its soft fins, limp body, lack of keels, asymmetrical tail, and inadequate calcification.
10. These Sharks Undergo Vertical Migration
Researchers put radio tags on a male megamouth caught in a net in 1990 and thrown back into the river. They tracked it for two days which revealed that the sharks undergo vertical migration.
11. They have an asymmetrical tail with a long upper lobe, but they do not have caudal keels
12. The Best Way to Eat Megamouth Meat is by Battering and Deep-frying.
After researchers have processed the 7th ever recorded megamouth in 1995, they couldn’t resist the urge to taste its piece. So, they dissected and analyzed it and then subject it to 3 methods of preparations of some dorsal muscle. In all, the battered and fried way turned out to be the best method for eating the Shark.
13. Megamouth Sharks Lives with the Whale Shark
Megamouth sharks live in the same habitat where the largest fish in the world lives (the whale shark).
14. Cannibalism May Happen in the Uterus of Female Megamouth Shark.
The young eat each other for survival; therefore, only the strongest are given birth to.
15. Researchers Only Observed 63 Megamouths Till 2014
Most of the observed specimen was either dead or enmeshed in various nets. Only four of them got released back into the ocean alive. While some were given to museums for research purposes, and others sold for consumption.
16. Megamouth sharks are timid sharks
17. The Very First Discovery of Megamouth Sharks was in 1976
After being caught in a deep-sea anchor by a navy ship. They then transported it to the National Marine fisheries service where scientists confirmed that it doesn’t have an already existing family or genus. As a result, they gave it a new family and genus.
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- “Confirmed Megamouth Shark Sightings”, Florida Museum.
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- “Megachasma pelagios (The Megamouth Shark)”, Sharkmans World.
- “Megamouth Shark”, Wikipedia. (accessed March 24, 2020)
- “Megachasma pelagios, Megamouth Shark”, IUCN Red List of Threatened Species.