Australian megamouth shark #3. Note the scar above the gill slits which may be the feeding scar of a Cookie-cutter shark. Source: Barry Hutchins/ Western Australian Museum

Introducing: Megamouth Shark

 

#59 caught last week in the Philippines
#59 caught last week in the Philippines

After it emerged last week that a rare deep-sea megamouth shark (Megachasma pelagios) washed up in the Philippines, I had a lot of people contacting me asking if it was even real. You bet it was real and here are some facts and photo’s to stimulate your inquisitive brains.

The first ever megamouth shark. #1. Photo: Hugh Gallagher
The first ever megamouth shark. #1. Photo: Hugh Gallagher

1. Only discovered in 1976

It was first discovered in Hawaii, just 38 years ago, in 1976 after accidently being caught in a deep-sea anchor. The large 4.46m shark was eventually transported to the National Marine Fisheries Service where it was later confirmed that neither the genus or species had previously been described.

Head of the Megamouth number 3, stranded at Mandurah, Western Australia 1988. Source: Barry Hutchins/ Western Australian Museum.
Head of the Megamouth number 3, stranded at Mandurah, Western Australia 1988. Source: Barry Hutchins/ Western Australian Museum.

2. Huge gaping of the sea

The scientific name Megachasma pelagios, translates from Latin into, huge (mega) gaping or yawning (chasma) of the sea (pelagios).

#59 caught last week in the Philippines
#59 caught last week in the Philippines

3. Only 59 documented sightings

As of writing this post, 06 July 2014, only 59 confirmed sightings have been documented (the 59th being the sighting last week in the Philippines). Most sightings have been in Taiwan, Japan and Philippines, and are usually a consequence of by-catch. They have also been found in the Atlantic, Indian and Pacific Oceans. A full list of the 59 megamouths can be found here.

 

Megamouth shark photographed after release. Source: Bruce Rasner
Megamouth shark photographed after release. Source: Bruce Rasner

4. Can reach nearly 6m long

The largest confirmed speciemen was a carcass found in Taiwan that measured a whopping 5.8m (~19 feet) but there have been suggestions that they can reach even bigger than this.

 

The closest living relatives to the megamouth is in fact the thresher sharks
The closest living relatives to the megamouth is in fact the thresher sharks. Source: Andy Murch

5. Closest relative is the thresher shark

Megamouths closest living relative is actually the thresher shark but you wouldn’t think it on looks alone.

Juvenile megamouth shark caught on Brazilian longline in 1995. Source Amorim et al 2000
Juvenile megamouth shark caught on Brazilian longline in 1995. From paper: Amorim et al 2000

7. Planktivorous engulfment feeder

The megamouth shark is one of only three known plankton feeding sharks, including the basking shark (Cetorhinus maximus) and the whale shark (Rhincodon typus). Whilst it was initially believed that this shark would suck in its mainly krill based diet, it is now believed that it performs engulfment feeding. Engulfment feeding is typical of baleen whales but this is the only species of shark that is thought to use this mechanism to feed [3].

From paper White et al 2004: A juvenile megamouth shark from Northern Sumatra, Indonesia
From paper White et al 2004: A juvenile megamouth shark from Northern Sumatra, Indonesia

8. Bioluminescent assisted feeding

It is believed that the slow swimming megamouth shark may make use of a highly reflective, luminescent mouth, which may act as a light trap to attract prey (imagine its mouth like an underwater electric flytrap found in kitchens). It has also been proposed that a bioluminescent strip above the mouth may also be used in a similar way, although neither of these behaviours have been proven.

The white strip above the mouth may attract prey items, such as krill, directly into the mouth.
The white strip above the mouth may attract prey items, such as krill, directly into the mouth. Engulfment feeding, like baleen whales, with added bioluminescence?

9. Automatic electronic food detectors 

Although they have the lowest abundance ampullary pores (electro-sensory organs) of any described shark, the arrangement of the pores “would allow for the detection of planktonic organisms around the head as the shark swims through the water (horizontally and vertically).

Filming after release: diving deep.
Filming after release: diving deep.

10. Twilight inspired movements

By acoustically tracking an individual shark in 1990, scientists were able to ascertain that this mysterious shark undertakes crepuscular (occurring during dusk and dawn) vertical migrations. During the daytime, the shark spent most of its time in deeper waters (400-500m) then at night, migrated to shallower waters. This behavior, often termed “diel vertical migration”, is common in other sharks and is typically associated with the following of prey items that adopt similar movements.

 

Australian megamouth shark #3. Note the scar above the gill slits which may be the feeding scar of a Cookie-cutter shark. Source: Barry Hutchins/ Western Australian Museum
Australian megamouth shark #3. Note the scar above the gill slits which may be the feeding scar of a Cookie-cutter shark. Source: Barry Hutchins/ Western Australian Museum

11. Preyed on by sharks and whales

Documented predators of the megamouth shark include sperm whales, orcas and other sharks. Various specimens have also washed ashore with circular shaped wounds torn from their flesh, which is typically indicative off cookiecutter shark predation.

#12 caught in Indian Ocean purse seine net
#12 caught in Indian Ocean purse seine net

12. Best way to be eaten is battered and deep fried. 

After processing the 7th  ever recorded megamouth shark specimen in 1995, researchers couldn’t resist the temptation of tasting a piece of this mystery creature they had just dissected and analysed. They were subsequently treated to 3 different preparations of some dorsal muscle. Battered & fried is apparently the best way to eat this shark!! [7]

“The next day Director Wakisaka had megamouth prepared, from a small piece of dorsal muscle, as a final treat for Jose and Genie: fried, poached with French sauce, and tempura style. Tempura was best”.

Clark, Eugenie, and José Castro et al pose with first female specimen (#6). From paper Clark & Castro 1995.
Clark, Eugenie, and José Castro et al pose with first female specimen (#6). From paper Clark & Castro 1995.

So that is the Megamouth shark. Rare, elusive, mysterious, plankton feeding giant of the deep.

How long and where until we get number 60??
How long and where until we get number 60?? Source: Bruce Rasner

See you next time for another “Introducing” where we will meet the velvet belly lantern shark (Etmopterus spinax).

Christopher Bird

(Twitter: @SharkDevocean)

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