Deep Water Sharks: Species, Characteristics and Unusual Evolutionary Adaptions

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gulper sharks

Sharks living below depths of 300 meters (984 feet) are considered deep sea sharks. They include some of world’s weirdest-looking creatures living on land or in the sea. Some parts of deep space are better explored than the deep ocean so there are likely many shark species down there that haven’t even been discovered yet. Among those we do know about the harsh dark environment and pressures have produced some stunning evolutionary adaptations. Though many have characteristics similar to those of sharks living closer to the ocean surface many deep water sharks also have unique biological features them make them unlike any other animal. Many live so deep that they are rarely seen and have been barely studied. Some have only been recently found. [Sources: Shark Sider, Hannah Ward, AZ, Animals, July 19, 2022]

Deep water sharks include gulper sharks, venomous schooling sharks that are small and feed mostly on small fish and crustaceans. They are heavily affected by overfishing. Swell sharks can double in size by swallowing water They are a species of catshark that lives in the Pacific Ocean, between California and southern Mexico and are typically found at depths around 500 meters (1640 feet) on rocky bottoms, hiding in rock crevices all day. They have a maximum size of around 1.1 meters (43 inches). When they feel threatened, swell sharks grab their tails in their mouths and suck in water, causing their stomachs to swell and making them look more threatening and harder for a predator to grab.

Pacific sleeper sharks can reach a length of six metres (20 feet) and go as deep as 2000 meters (6562 feet). A 15 meter beast was purportedly snapped in the Mariana Trench in 2016 — sparking rumors that ancient megalodon (giant great-white-shark like creatures) still existed. They are found in the Pacific Ocean and have been spotted off the coasts of Japan, the Russian Far East, southern California, Mexico and Australia. [Source: 9 News, Australia]

The deepest-living shark is the Portuguese dogfish or Portuguese shark (Centroscymnus coelolepis). This relatively small shark grows to about one meter (3.3 feet) in length and are benthic, meaning they live on the ocean floor. They have been found as deep as 3,675 meters (12,057 feet, according to the Florida Museum of Natural History(opens in new tab). Widely distributed around the world's oceans and belonging to the sleeper shark group of fish, Portuguese dogfish are typically black or dark brown in color, have round, flattened snouts and small spines in front of their dorsal fin. and possess approximately 98 teeth, which use to grab bony fish, cephalopods and other sharks. .[Source: Stephanie Pappas, Live Science, July 25, 2022]

Frilled Sharks

The frilled shark (Chlamydoselachus anguineus) is a two-meter-long deep water shark that looks like an a long, fat eel. It has frilled gill slits, needle sharp teeth and a triangular head. Normally found at depths below 600 meters (1970 feet), it is sometimes called a “living fossil” because it has changed little in 80 million years.

Frilled sharks get their name from their unusual gill filaments that form a frilled crown around their head. These gills are not separate as is the case with most fish; instead they circle all the way around the shark's throat. Frilled sharks eat smaller sharks, bony fish, squid, and octopus. Scientists believe strike at prey like a coiled snake, using their back fins to propel them forward, lunging at prey, snatching it with the a jaw with 25 rows of backward-facing teeth, and swallowing it whole. [Source: by Hannah Ward, AZ, Animals, July 19, 2022]

Frilled sharks look so strange it doesn't seem implausible that they gave birth to the myth of sea serpents. They live over the upper continental slope in the Atlantic and Pacific oceans in water up to 1188 meters (3,900 feet). They are occasionally caught as bycatch and have been captured in water as deep as 1,570 meters (5,150 feet). Live Science called them "the weirdest shark in the sea", saying "These elusive living fossils been trolling the deep seas, snagging prey with their 300 prong-pointed teeth, since before the dinosaurs died out. Because they live so deep, frilled sharks are rarely seen.... Given their rows of backward teeth and ominous, club-like heads, maybe that's a good thing. [Source: Stephanie Pappas, Live Science, July 25, 2022]

Frill sharks have unusually large livers for their size that helps them stay buoyant and maneuver in highly-pressurized deep water. One frilled shark was filmed alive near the surface off of Japan in 2007 and became a You Tube sensation. The creature was spotted by fishermen who alerted an aquarium that moved it to a seawater pool where it was filmed. The 1.6-meter (five foot) shark appeared to be in poor health and died a few hours after being caught.

Lanternsharks and Luminous Deep Water Sharks

The Dwarf lanternshark (Etmopterus perryi) is the world's smallest shark species. It also one of the deepest living sharks. This tiny creature grows to be only about 20 centimeters (7.9 inches) long. It's rarely observed, given that it swims at depths between 283 and 439 meters (928 and 1,440 feet) below the sea surface. See World’s Smallest Sharks Under SHARK SPECIES:

The kitefin shark is the world's longest known luminous vertebrate. A 1.8-meter (six-foot) specimen was captured in 2020 during a fish survey off the coast of New Zealand. This fish is normally found between depths of 200 and 1,000 meters (660 and 3300 feet) but some have been caught as deep as 1,800 meters (5,900 feet). In the "Twilight Zone" where they live light does not penetrate and it is thought bioluminescence acts as a form of camouflage from predators striking from below. [Source: 9 News, Australia]

Kitefin sharks live in several populations around the world in tropical and subtropical waters close to the sea floor. They have very short, round snouts and their average length is around 1.3 meters (4 feet). Like cookiecutter sharks, kitefin sharks have the ability to take huge chunks out of much larger animals, including whales. They prey on a wide variety of animals, including smaller sharks, skates, and bony fish. [Source: by Hannah Ward, AZ, Animals, July 19, 2022]

Velvet belly lanternshark (Etmopterus spinax)

The ninja lanternshark is another small, luminous, deep sea shark — only 50 centimeters (20 inches) — that was only discovered in 2010.They are found along the continental slope in the eastern Pacific Ocean at depths of 835 to 1,433 meters (2,740 to 4,735 feet). These fish are black and have white markings around their mouths. Their luminousity acts as both camouflage and attracts prey. When they are feeding in shallower waters their luminous belly has the same appearance as the sunlight filtering down from above and camouflages them from would-be predators below. However, when they are in the deepest depths of the ocean, their luminous appearance attracts smaller prey to them. According to 9 News, “The ninja lanternshark’s unique name comes from four children. Vicky Vásquez, the researcher who found the shark, asked her young cousins what they would call a nearly all black shark that glows. [Source: by Hannah Ward, AZ, Animals, July 19, 2022; 9 News, Australia]

Goblin Shark

Goblin Sharks (Mitsukurina owstoni) are bizarre-looking deepwater sharks that generally reach 3.3 meters (11 feet) in length and weighs as much as 160 kilograms (350 pounds). There are examples of bigger ones. One caught in 2000 is thought to have been six meter (20 feet) long. These sharks have changed so little tens of millions of years they have been described as living fossils. Goblin sharks are rarely seen by humans. They are relatively rare deep-water shark living in all major oceans.

Goblin Sharks have a long, flat snout and toothy jaws that protrude in front of the face to catch unsuspecting prey. The fish were described as “grotesque” when first encountered in 1910. The goblin shark is the only living representative of its family, Mitsukurinidae, and is the most evolutionarily distinct shark we know of. It’s lineage stretches back some 125 million years. [Source: Alice Clement, Research Associate in the College of Science and Engineering, Flinders University, The Conversation October 10, 2022]

Greenland Sharks

Greenland sharks are the longest-living shark and also the longest-living vertebrate (all mammals, birds, reptiles, amphibians and fish). They have been known for a long time to live for a really time. 2016 research that dated the layers in the sharks' eye lenses found that the sharks were between 272 and 512 years old. [Source: Stephanie Pappas, Live Science, July 25, 2022]

Greenland sharks (Scientific name: omniosus microcephalus) are also known as sleeper sharks, ground sharks, gray sharks, and gurry sharks. They are known as ekalugssuak in Greenland, hakarl in Iceland, and hakjerring in Norway. The Greenland Shark is known for being the primary ingredient of the infamous Icelandic dish “Hakarl,” By some reckonings it is the second largest carnivorous shark in the world, after the great white shark. They are the only sharks that can survive the cold of the Arctic Ocean all year. They have extremely slow metabolisms and grow only about a centimeter (0.39 inches) a year. Over their long lives they can reach lengths of six meters (19.7 feet). [Source: Live Science, Patrick Mills, Animal Diversity Web (ADW) /=]

Greenland shark

Bluntnose Sixgill Sharks— Living Fossils

Bluntnose sixgill sharks (Scientific name: Hexanchus griseus) are also known as sixgill sharks, sixgilled sharks, six-gill sharks, cow sharks, gray sharks and mud sharks. They are mainly shy, deepwater sharks. Live specimens have been rarely observed and efforts to keep them in captivity have been hindered by stress due to their light-sensitive eyes and their large size. [Source: Jessica Bauml, Animal Diversity Web (ADW) /=]

Bluntnose sixgill get their name from the fact that they have six pairs of gill slits instead of the more common five. They more closely resemble now extinct sharks from the Triassic Age (252 million to 201 million years ago) than modern sharks. Like other prehistoric sharks they have one dorsal fin on their lower backs, instead of the usual two, and large pectoral fins. Victor G. Springer wrote in the Washington Post: During the Jurassic Period between 205 million and 135 million years ago, the first sharks representing extant shark families or genera appeared. Among these are horn or bullhead sharks, Heterodontus, and sixgill sharks, Hexanchus. Sixgills are live bearers found worldwide, usually in relatively deep water. The largest species attains a length of almost five meters (16 feet). Horn sharks are small, egg-laying species, usually less than four feet long, living in shallow waters — divers often can approach them — and found almost exclusively on the temperate coasts of the Indian and Pacific oceans. [Source: Victor G. Springer, National Museum of Natural History Washington Post November 11, 1998]

The most widely distribution of all known sharks, with the possible exception of white sharks, bluntnose sixgill sharks occur globally in all oceans, including the Indian Ocean, Atlantic Ocean, Pacific Ocean and Mediterranean Sea. They have been found at depths of three to 2,500 meters (10 to 8,200 feet) but are mainly a deep water shark, rarely encountered at depths of less than 100 meters. The species seems to usually stay close to the bottom, near rocky reefs or soft sediments. The deepest one has been found was about 2500 meters. These sharks migrate vertically on a daily basis, remaining in the deep oceans during the day and rise towards the surface at night. Bluntnose sixgill sharks also seasonally migrate to shallower coastal waters. During the warmer months of the year, these sharks are occasionally observed found in shallower waters at depths of 23 to 39 meters (75 to 128 feet) during the day and as shallow as three meters (10 feet) at night. /=\

The bluntnose sixgill shark is classified under the genus Hexanchus with only one other species, Hexanchus nakamurai, or the bigeyed bluntnose sixgill shark. Both sharks are similar in all aspects except the later is smaller. Bigeyed bluntnose sixgill shark only reaches about 2.3 meters (7.5 feet) in length while the bluntnose sixgill shark reaches lengths of 4.8 meters (16 feet). /=\

Bluntnose sixgill shark

Bluntnose Sixgill Shark Characteristics and Behavior

Bluntnose sixgill sharks are large sharks with a heavy build. They range in weight from 480 to 720 kilograms (1057 to 1586 pounds), with their average weight being 500 kilograms (1100 pounds). They range in length from 3.5 to 4.8 meters (11.5 to 15.8 feet), with their average length being 3.7 meters (12.1 feet). Females are slightly larger than males but otherwise they look pretty much the same however, the seasonal scars appearing on the fins of females, which are believed to be a result of mating, are commonly used for sex identification. Sex can be easily determined by the presence of elongate claspers on the pelvic fins of male sharks. [Source: Jessica Bauml, Animal Diversity Web (ADW) /=]

According to Animal Diversity Web: These sharks have a short, blunt snout, a broadly rounded mouth, and six pairs of gill slits (from which its common name, the bluntnose sixgill, is derived). They have large, green eyes and broad comb-like teeth on each side of the lower jaw arranged in six rows. Their coloring shades varies from grayish-black to chocolate brown on the dorsal surface and lightens to grayish-white on its belly. There is an anal fin, and one dorsal fin located on the back end of the body. The caudal fin is slightly raised so that the lower lobe is lined up with the body axis. The pelvic fins are located to the anterior of the anal fin and are a bit larger. Like many benthic (living on or near the bottom of the sea) sharks, the caudal fin of Bluntnose sixgill sharks has a weakly developed lower lobe. However, the bluntnose sixgill shark is still a very strong swimmer.

Bluntnose sixgill sharks are mainly solitary animals. and most likely never swim in schools or seek out interaction. Some researchers, however, have speculated that bluntnose sixgill sharks return to shallow waters year after year (during the months of May to November) in order to interact socially with other bluntnose sixgill sharks, most likely for the sole purpose of mating. Richard Martin suggests that these light-sensitive sharks are drawn up to the shallower depths due to the yearly summer algae bloom which greatly increases light attenuation, allowing the sharks comfort while providing them with more prey items. During these seasonal interactions, males are believed to nip at the gills of females to court the females. During non-mating season, Bluntnose sixgill sharks remains at the lower depths rising only to feed at night. The only known form of communication to occur in Bluntnose sixgill sharks is during mating. The males are believed to use their teeth to entice the females into mating.

Bluntnose Sixgill Shark Feeding and Mating

Bluntnose sixgill sharks are skilled predators. They feed on fishes, rays, and other sharks. According to Animal Diversity Web (ADW): These sharks are equipped with very sensitive perception organs, which may allow them to detect potential predators. The retinas are comprised of mostly rods and, therefore, do not function well in even moderately lit areas but are well suited for the dark conditions of the deep oceans. Although they have been reported as being sluggish in nature, their body structure enables them to reach remarkable speeds for chasing and effectively capturing prey. Aside from feeding on molluscs and marine mammals, they eat crustaceans (crabs and shrimp), agnathans (Hagfish and sea lampreys), chondrichthyans (ratfish) and teleosts (dolphinfish and lingcod). A subspecies of Bluntnose sixgill sharks living in Cuban waters is also a skilled scavenger that feeds on carcasses of mammals.

Bluntnose sixgill sharks are ovoviviparous, meaning that eggs are hatched within the body of the parent. They engage in seasonal breeding and engage in internal reproduction in which sperm from the male fertilizes the egg within the female. The breeding season is from May to November. The number of offspring ranges from 22 to 108. Females reach sexual or reproductive maturity at 18 to 35 years.

Very little is known about these sharks in terms of their social behavior and thus little is known about their mating systems . There are a few theories, however, attempting to explain how Bluntnose sixgill sharks mates. Researchers believe that the morphology of the teeth of Bluntnose sixgill sharks play an important role in mating. The male has a more erect primary cusp than do the females. The male is believed to nip the female's gills with this cusp in order to catch her attention and entice her into mating. Evidence supporting this idea of courtship is evident by the seasonal scars that appear on females every year presumably from being nipped by males.Bluntnose sixgill sharks are believed to be primarily solitary animals and there is no information indicating whether they prefer one or many mates. /=\

Scientists are unsure of the bluntnose sixgill shark's gestation period, but it is thought to be longer than two years. Babies develop within the mother without a placenta to provide nourishment, and they are born at a fairly mature size (generally 70 centimeters at birth). Little is known about their lifespan or maturation because until recently determining their age was difficult as a result of their poorly calcified vertebrae. The pups of Bluntnose sixgill sharks, however, are speculated to mature around 11 to 14 years for males and 18 to 35 years for females.

Image Source: National Oceanic and Atmospheric Administration (NOAA); Wikimedia Commons

Text Sources: Animal Diversity Web (ADW); National Oceanic and Atmospheric Administration (NOAA); Wikipedia, National Geographic, Live Science, BBC, Smithsonian, New York Times, Washington Post, Los Angeles Times, The New Yorker, Reuters, Associated Press, Lonely Planet Guides and various books and other publications.

Last Updated March 2023

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