A rare and mysterious species, the Megamouth Shark Megachasma pelagios was first sighted when one had gotten entangled in a sea anchor (Oceana, 2023), and hauled up by fishermen on-board a navy ship in 1976 (Black, 2014). The Megamouth Shark is distributed worldwide in tropical to temperate latitudes, can be found in costal to open ocean (epipelagic to bathypelagic), and is a filter feeder, like that of the Whale, and Basking Shark (Oceana, 2023).

Upon its first discovery, this genus of shark generated its own taxonomy, Order Lamniformes (mackerel sharks), and belongs to the family Megachasmidae (megamouth sharks) (Oceana, 2023). Currently this shark is listed as least concern on the IUCN Red List, with the most recent assessment of species health being in 2018 (IUCN Red List, 2023). The Megamouth Shark can be found resident in countries such as Australia, Sri Lanka, Vietnam, South Africa, and China, with the current population number of sharks being unknown due to their rare sightings, and lack of research (IUCN Red List, 2023).

A large species of shark, reaching weights of up to 2700 pounds (1215kg), and approximately 16 feet in length (5m), this species has only been observed within the wild a few times, with less than 60 individual sharks having been known by scientists to of ever been captured or observed (Oceana, 2023). The smallest of the three species of filter-feeding sharks, this shark derived its name from its remarkably large, circular mouth (Oceana, 2023). From what little research has been carried out on the species, from the rare few sightings these sharks have been observed residing near to the surface, in depths of up to 15,000 feet (4600m) (Oceana, 2023).

It is believed that Megamouth sharks only come near to the surface at night, spending the majority of their lives in the dark (Oceana, 2023). They are filter feeders that swim through the ocean with their mouths open capturing food resources, such as plankton (Oceana, 2023). The inside of their mouths contain light producing organs, believed to be used for attracting pelagic crustaceans and other prey (Oceana, 2023).

With commercial fisheries pushing to deeper depths to discover new species to market as food, more and more large deep sea creatures are being discovered (Oceana, 2023). Like other species of shark, megamouths mate via internal fertilization, giving birth to a small number of live young (Oceana, 2023). The adult shark does not connect to their live young through a placenta, and instead the mother provides an unfertilized egg during gestation (Oceana, 2023). Once born, the megamouth shark immediately becomes a filter feeder (Oceana, 2023). There is a huge lack in species behavioral ecology, and richness, and so electronic tagging studies and further research is needed in order to better understand, and to conserve this species (Watanabe & Papastamatiou, 2019).

SCIENTIFIC NAME: Megachasma pelagios

FAMILY: Megachasmidae

MAXIMUM SIZE: Up to 5.5 meters (18 feet) in length

DIET: Filter feeds for plankton, but also consumes deep water fish

DISTRIBUTION: Widespread distribution in tropical and temperate waters worldwide

HABITAT: Ocean-going. Surface to deep waters – 1,000m.

CONSERVATION STATUS:

Due to its elusive nature and rare sightings, little is known about its population size or trends. It is occasionally caught as bycatch in fishing gear, but there are no known directed fisheries for this species.

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Banner image – Wikimedia Commons | GordonMakryllos

References:

• Black, R. (2014) A forgotten fossil megamouth gets a name. National Geographic. Available at: https://www.nationalgeographic.com/science/article/a-forgotten-fossil-megamouth-gets-a-name. Accessed: 21^st March 2023.
• IUCN Red List. (2023) Megamouth Shark. IUCN Red List. Available: https://www.iucnredlist.org/species/39338/124402302#taxonomy. Accessed: 21^st March 2023.
• (2023) Megamouth Shark. Oceana. Available at: https://oceana.org/marine-life/megamouth-shark/. Accessed: 21^st February 2023.
• Watanabe, YY, Papastamatiou, YP. (2019) Distribution, body size and biology of the megamouth shark Megachasma pelagios. J Fish Biol. 95: 992– 998. https://doi.org/10.1111/jfb.14007

This month’s Creature Feature has a guest writer – Jodie Moore

This month we’re talking about some sharks with unusual names. With names that range from the descriptive to the downright strange. Let’s look at three species with weird and wonderful names!

Tasseled Wobbegong

The Tasseled Wobbegong (Eucrossorhinus dasypogon) is a species of carpet shark found in the shallow coral reefs of the Indo-Pacific. This unique shark gets its name from the tassels that hang from its chin and the sides of its head, making it look like it’s wearing a fancy carpet. The scientific name of the Tasseled Wobbegong, Eucrossorhinus dasypogon, comes from the Greek words “eu” meaning good, “krossoi” meaning fringe, “rhinos” meaning nose, and “dasys” meaning hairy, and “pogon” meaning beard, referring to the shark’s characteristic tassels.

The Tasseled Wobbegong has a broad, flattened head and a body that is covered in small, thorn-like projections. These projections, called dermal denticles, are a common feature of shark skin and help to protect the shark from predators and parasites. The Tasseled Wobbegong’s skin is also covered in a unique pattern of dark spots and stripes that allows it to camouflage itself on the reef floor. With their striking appearance and docile nature, they are a favorite of divers and underwater photographers.

Despite their wild appearance, Tasseled Wobbegongs are relatively docile and are known to be tolerant of human divers. They are primarily nocturnal, spending most of their days hiding in crevices and under overhangs on the reef. At night, they venture out to hunt small fish and crustaceans, using their powerful jaws to crush their prey.

Although the Tasseled Wobbegong is not considered to be a threatened species, it is facing increasing pressure from habitat degradation and overfishing. In 2018, the International Union for Conservation of Nature (IUCN) listed the Tasseled Wobbegong as a species of “Least Concern” on their Red List, which is a positive sign that the population is currently stable.

SCIENTIFIC NAME: Eucrossorhinus dasypogon

FAMILY: Orectolobidae

MAXIMUM SIZE: 122cm

DIET: Bony fish, crustaceans, and cephalopods

DISTRIBUTION: Found in the waters around southern Australia, including Tasmania and the Bass Strait.

HABITAT: Shallow, coastal waters with rocky or coral reefs, as well as seagrass beds and sandy areas.

CONSERVATION STATUS: 

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Crocodile Shark

This unique species (Pseudocarcharias kamoharai) is a small and slender-bodied shark. Which was only disovered in 1985! The genus name, Pseudocarcharias, means “false shark,”. While the species name, kamoharai, honors the Japanese ichthyologist, Kamohara. The English common name “crocodile shark” is derived from its Japanese name mizuwani (水鰐, literally “water crocodile”), which refers to its sharp teeth and habit of snapping vigorously when taken out of the water.

The Crocodile Shark is named for its distinct crocodile-like appearance, with a long snout and sharp teeth. With a maximum length of 1.2 meters. This species is found in deep ocean waters around the globe, from the Atlantic to the Indian Ocean, typically at depths of 200 to 500 meters. However, it has been known to venture as deep as 1,000 meters.

What makes the Crocodile Shark particularly unusual is its opportunistic feeding behavior. This means that it will eat just about anything it comes across. Including small fish, squid, and even other sharks. The Crocodile Shark uses a unique hunting technique to catch its prey. Its slender body and elongated snout allow it to navigate through tight spaces and ambush unsuspecting prey, making it a formidable predator despite its small size.

Since being discovered, we’ve not uncovered much about this elusive species. Not much is known about the biology and behavior of Crocodile Sharks. They are rarely encountered. And in 2019, the Crocodile Shark was listed as “data deficient” on the IUCN Red List. This means that not enough is known about the species to determine its conservation status. This elusive species’ DNA has been analysed and they are determined to be closely related to the Megamouth Shark or sand sharks (Odontaspididae). Alternative research, analysis based on teeth structure, suggests that the closest relatives of the crocodile shark are the thresher sharks.

SCIENTIFIC NAME: Pseudocarcharias kamoharai

FAMILY:  Pseudocarchariidae

MAXIMUM SIZE: 1.2m

DIET: Bony fish and cephalopods

DISTRIBUTION: They are found in tropical and warm temperate waters around the world, including off the coasts of Japan, Australia, South Africa, and Brazil.

HABITAT: Deep offshore waters, typically at depths of 200 to 500 meters, but have been known to come up to shallower depths at night to feed.

CONSERVATION STATUS:

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Viper Dogfish

The Viper Dogfish (Trigonognathus kabeyai) is a species of deep-sea shark found in the North Pacific Ocean. This unique shark gets its name from its distinctive appearance, which resembles that of a viper snake, due to the long, fang-like teeth protruding from its jaws. The scientific name comes from the Greek words “trigonos” meaning triangular, “gnathos” meaning jaw, and “kabeya” in honor of the late Japanese ichthyologist, Toshiji Kabeya, who made significant contributions to the study of deep-sea sharks.

The Viper Dogfish is a relatively small species of shark, growing up to just 40 centimeters in length. Its body is slim and elongated, with a dark brown or black coloration that allows it to blend in seamlessly with its deep-sea environment. They’re typically found at depths of between 365 and 1,200 meters, where they feed on a variety of prey including small fish, squid, and crustaceans. Their long, fang-like teeth allow them to easily catch and hold onto their prey, despite their small size.

Despite being a relatively unknown species, the Viper Dogfish has been listed as a species of “Least Concern” on the International Union for Conservation of Nature (IUCN) Red List.

SCIENTIFIC NAME: Trigonognathus kabeyai

FAMILY: Etmopteridae

MAXIMUM SIZE: 40cm

DIET: Small fishes and invertebrates

DISTRIBUTION: Northwest and central Pacific: Japan, Taiwan and Hawaiian Islands.

HABITAT: Deep waters, between 250 – 1000m. Possibly oceanic as some have been caught at 150m over water as deep as 1500m.

CONSERVATION STATUS: 

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Banner Image – © Frogfish Photography

Wobbegong – © Andy Murch

Crocodile Shark – © Dianne J. Bray, 2011, Crocodile Shark, Pseudocarcharias kamoharai, in Fishes of Australia, accessed 11 May 2014, http://www.fishesofaustralia.net.au/home/species/3001 | Wikimedia Commons

Viper Dogfish – © Stephen M Kajiura | Wikimedia Commons