Latin name

Megachasma pelagios

Other names

Megachasma pelagios

Identification

The most noticeable external feature that gives this shark its name is a large rounded head with a short nose and a large mouth. The head can be as long as the body. The snout is very short, flattened and rounded. The eyes are quite large, ranging from 1.6 to 1.8% of the length of the body. The gill slits are elongated, their length is 6.4-8.6% of the body length. They do not extend to the dorsal surface of the head. The last two gill slits are located above the pectoral fins. The gills are equipped with finger-like dermal projections (stamens) with cartilage on the inside. They line the outer surface of the gill slits. The mouth is very large and arched. The jaws are strongly protruding. Teeth small, awl-shaped. The body is cylindrical, stout, flattened and slightly flabby. The caudal peduncle is compressed and the lateral keels are absent. There is a small precaudal notch. The placoid scales are very small and soft. The vertebral column is poorly calcified. The total number of vertebrae is 151, the vertebrae in the trunk of the spine are 64. The spiral valve of the intestine has 23-24 turns.

Features of fish fins

The coloration of the back of these sharks is dark brown, and the belly is lighter.

Fish colouring

The largemouth shark has two dorsal fins and an asymmetrical caudal fin. The upper lobe of the caudal finis elongated and the lower lobe is short but strong. The pectoral fins are large, slender and elongated. The pelvic fins are medium-size, smaller than the pectoral fins and the first dorsal fin. The first dorsal fin is quite large, triangular in shape, the second dorsal fin is 2 times smaller. The base of the first dorsal fin is posterior to the base of the pectoral fins. The base of the second dorsal fin is between the bases of the pectoral and anal fins.

Distribution

They are found in the Atlantic, Pacific and Indian Oceans. They have been most commonly found off the coasts of Japan, Taiwan and the Philippines. From this, biologists conclude that the species is globally distributed and prefers relatively warm latitudes.

Habitat

This pelagic fish is found both in the neritic zone and in the open sea. It is found in shallow bays at depths from 5 m to the continental shelf at a depth of 40 m, as well as in the open sea up to 1500 m, usually in the range of 120-166 m. The color and fat content in the liver indicate that it is an epipelagic rather than a deep-sea species.

Size

The maximum record length is 5.7 m. The smallest specimen was a male measuring 1.77 m.

Behavior

They make vertical movements. Sharks spend the night at a depth of about 12-25 m, and at dawn they descend to a depth of 120-160 m. Probably the fish follows the krill, which changes its depth location. When choosing depth, sharks are guided by the level of light. Despite their low activity, they are able to move at a cruising speed of about 1.5-2.1 km/h for long periods of time.

Food and feeding habits

These sharks filter their food and their diet is based on small organisms such as krill. Oar-footed crustaceans and jellyfish have also been found in their stomachs. The megamouth shark probably swims through the mass of krill with its mouth wide open, periodically closing its jaws and squeezing its throat to seal the food before swallowing. The mouth has a bright silver rim that glows and is a light trap for krill. It becomes visible when the shark pushes its upper jaw forward. The ability to extend their jaws forward allows sharks to suck in food.

Reproduction

The ovaries of the megamouth are similar to those of other mackerel sharks, and it is likely that this species also reproduces by placental birth with oophagy.

Fishing

Due to the fact that this species is extremely rare, it is not of commercial interest, although it's meat has been seen on several occasions being sold in local markets. Occasionally these sharks are caught as bycatch, but they are usually thrown overboard because they are too large.

Relationship with a person

Despite their impressive size, largemouth sharks are not dangerous to humans. They are highly prized as exhibits in aquariums and museums.