Sixgill shark
The sixgill shark, scientifically known as Hexanchus griseus, is a distinctive marine species characterized by its six gill slits, which sets it apart from the more common five-gilled sharks. Typically gray-brown to dark gray on its dorsal side and lighter underneath, this shark can grow to about 15 feet (4.5 meters), with some individuals reported to reach lengths of up to 26 feet (8 meters). It is recognized for its sluggish swimming style and notable physical features, including large emerald green eyes and a dorsal fin positioned almost directly above its anal fin.
Sixgill sharks inhabit the deeper waters of the Atlantic Ocean, Mediterranean Sea, Pacific Ocean, and parts of the Indian Ocean, often residing at significant depths. Their diet includes a variety of marine life such as hake, crabs, and small marlin, and they tend to feed more actively at night. Reproduction in sixgill sharks involves ovoviviparity, where the young develop in eggs within the female and are born live. Additionally, they are targeted in fishing activities, particularly in regions like Cuba, where they are caught for their flesh and oil. Despite their unique features and ecological role, much about their mating habits remains poorly understood.
Subject Terms
Sixgill shark
The sixgill shark is named after the extra gill it has on either side of its body, giving it a total of six gills, rather than the usual five. The sixgill shark is a slow-moving, sluggish species.
Animalia
Phylum: Chordata
Class: Chondrichthyes
Order: Hexanchiformes
Family: Hexanchidae
Genus: Hexanchus
Species: Griseus
The sixgill shark is gray-brown to dark gray on the top of its body and paler below. It reaches a full-grown length of about 15 feet (4 1/2 meters). Some have been reported growing as long as 26 feet (about eight meters) The species gets its name from the six gill slits located just ahead of its pectoral fins. The fact that other sharks have five gill slits makes this species unique. The dorsal fin of the sixgill shark is located almost directly above its anal fin. Both the dorsal and anal fin are roughly the same size. The caudal, or tail, fin is long and measures about half the length of the sharks body, minus the tail. The sixgill shark has large, wide emerald green eyes. The young sixgill shark is a slate-grey color.
The sixgill shark inhabits the deeper waters on both sides of the Atlantic Ocean as well as the Mediterranean Sea. In the Pacific Ocean, it exists from British Columbia to southern California and Chile, and off the coasts of Japan and Australia. It also inhabits the southernmost regions of the Indian Ocean and off South America.
The diet of the full-grown sixgill shark consists of hake, dolphin, crab, shrimp, small marlin, and swordfish. They are known to feed more aggressively at night when they rise from the murky depths toward the surface.
Very little is known about the mating habits of sixgill sharks. After the male and female mate, the young develop within eggs within the female. The young hatch from these eggs while still inside the female and are then born live. This process of reproduction is known as ovoviviparity.
In Cuba, sixgill sharks are commonly caught using a fishing line dropped over the side of a boat. The line travels deep down into the water where the sixgill shark lives. The flesh of the sixgill shark is used for oil.
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“Hexanchus nakamurai Bigeye Sixgill Shark.” Animal Diversity Web, animaldiversity.org/accounts/Hexanchus‗nakamurai/classification. Accessed 23 Apr. 2024.
“Sixgill Shark.” A-Z Animals, 23 July 2021, a-z-animals.com/animals/sixgill-shark. Accessed 23 Apr. 2024.