- Related Topics:
- shark
- Mollisquama parini
- American pocket shark
pocket shark
-
What is a pocket shark?
The pocket shark is a small, deepwater shark known for the presence of internal pockets near its pectoral fins. They are closely related to kitefin sharks, cookie-cutter sharks, and the pygmy shark.
Very little is known about the ecology and natural history of pocket sharks. Most deepwater shark species are relatively small, seldom reaching 2 meters (6.5 feet) in length. The American pocket shark was only 14 cm (5.5 inches) in length. They have cigar-shaped bodies and rounded heads. Pocket sharks are viviparous, giving birth to live young.
Pocket sharks have an internal pocket gland located just above each pectoral fin. These glands may secrete a bioluminescent fluid to blind and confuse predators or lure prey. The American pocket shark also has photophores (light-emitting organs) spread across its body.
Pocket sharks are found in different parts of the world. The pocket shark (Mollisquama parini) was discovered near the Nazca Ridge in the southeast Pacific Ocean in 1979. The American pocket shark (M. mississippiensis) was collected in the northern Gulf of Mexico in 2010. Both species were collected from mid-water trawls at depths between 330 and 580 meters (approximately 1,100 and 1,900 feet).
2 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
Where was the pocket shark first discovered?
The first pocket shark (Mollisquama parini) was discovered in 1979 near the Nazca Ridge in the southeast Pacific Ocean. In 2010, a second specimen, a juvenile male, was collected in the northern Gulf of Mexico and was later classified as a separate species, the American pocket shark (M. mississippiensis). Pocket sharks are small deepwater sharks known for the presence of internal pockets located near their pectoral fins. They are closely related to kitefin sharks. Both species were collected from mid-water trawls at depths between 330 and 580 meters.
1 Britannica SourceCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
How big does a pocket shark grow?
Pocket sharks are deepwater sharks, and most deepwater shark species are relatively small, seldom reaching 2 meters (6.5 feet) in length. The American pocket shark (M. mississippiensis) was only 14 cm (5.5 inches) long. Pocket sharks have cigar-shaped bodies and rounded heads, unlike many other shark species with pointed snouts.
Two pocket shark species are known: Mollisquama parini, and the American pocket shark (M. mississippiensis). They have internal "pocket" glands near their pectoral fins, which may secrete bioluminescent fluid to confuse predators or lure prey.
1 Britannica SourceCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
What is unique about the pocket shark compared to other sharks?
Pocket sharks are small, deepwater sharks, closely related to kitefin sharks. The pocket shark is unique due to the presence of internal "pocket" glands above each pectoral fin. These pockets open through slits and are lined with specialized cells. While it was initially thought they secrete pheromones to attract mates, current studies suggest these glands produce a bioluminescent fluid. This fluid may serve to blind predators or attract prey. The American pocket shark also has photophores, or light-emitting organs, on its body.
Pocket sharks are viviparous, giving birth to live young that are nourished inside the female. They are known from only two specimens collected in 1979 and 2010. The pocket shark was found near the Nazca Ridge in the Pacific Ocean, and the American pocket shark was discovered in the Gulf of Mexico.
1 Britannica SourceCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
What are the 'pockets' used for in the pocket shark?
The pocket shark gets its name from a unique physical feature: a pair of internal "pocket" glands located above each pectoral fin. These pockets distinguish them from other shark species.
Although the exact function of these pockets is not definitively known, scientists have two main hypotheses. One idea is that they secrete pheromones, acting as sex attractants to help the sharks find mates in the deep ocean. However, the prevailing theory, supported by anatomical studies, suggests that the pockets produce a bioluminescent fluid. This fluid could serve to confuse predators or attract potential prey in the dark depths.
1 Britannica SourceCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
How do scientists study rare animals like the pocket shark?
Scientists study rare animals like the pocket shark using various methods to gather data and insights. Due to the limited number of pocket shark specimens, much of the research relies on analyzing physical features to infer their life history.
Sampling devices like plankton nets and midwater trawls are used to collect specimens. Technology such as acoustic telemetry, satellite tags, and DNA bar coding aid in monitoring and cataloging these organisms. These tools help track movements, identify species, and understand their distribution.
The study of pocket sharks also involves examining their habitat. They have been found at depths between 330 and 580 meters (approximately 1,100 and 1,900 feet). Studying their physical characteristics, such as the pocket gland and photophores, provides clues about their behavior and ecological role.
4 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
pocket shark, (genus Mollisquama), either of two species of enigmatic small deepwater sharks known for the presence of internal pockets located near their pectoral fins. Pocket sharks are known from only two specimens, collected in 1979 and 2010 from different marine environments. The pocket shark is most closely related to the kitefin sharks (Dalatias licha), another typically deepwater species classified within the family Dalatiidae. The cookie-cutter sharks (Isistius) and the pygmy shark (Euprotomicrus bispinatus), which are among the smallest shark species known, are probably the pocket shark’s best-known relatives.
Classification and distribution
Detailed information about the habitat and distribution of pocket sharks is scant; what is known about the group has been derived from two specimens collected in very different parts of the world. The pocket shark (Mollisquama parini) was described in 1984 from a single specimen of a large female collected near the Nazca Ridge in the southeast Pacific Ocean in 1979. A second specimen, a juvenile male, was collected in 2010 in the northern Gulf of Mexico and first described in 2015; however, it was not until 2019 that it was formally classified as a separate species, the American pocket shark (M. mississippiensis). Both species were collected from mid-water trawls at depths between 330 and 580 metres (approximately 1,100 and 1,900 feet), with the actual seafloor depth in each habitat being considerably deeper (2,000–3,000 metres [roughly 6,600–9,800 feet]).
Natural history
Although very little is known about the ecology and natural history of pocket sharks, some of their physical features may provide clues to their life history. The pocket shark resembles many other deepwater shark species, most of which are relatively small, seldom reaching 2 metres (6.5 feet) in length. The American pocket shark was only 14 cm (5.5 inches) in length. Pocket shark bodies are cigar-shaped, and they lack the pointed snouts typical of many other shark species, having instead a generally rounded head. Although the small size and the delicate condition of the two specimens has prevented detailed studies of gut contents to examine the shark’s feeding choices, the presence of sharp and pointed teeth in both specimens suggests that pocket sharks may be effective predators.
" height="20" alt="HEW Logo">
Pocket sharks are viviparous: they give birth to live young. The young possess a yolk sac and are nourished inside the female until they are born. The details surrounding the pocket shark’s litter size, gestation period, and mating and nursery grounds are unknown. However, the presence of a yolk sac scar on the small juvenile male American pocket shark suggests that it was newly birthed and that its capture site may be an area where young are born.
One of the main physical features that distinguishes pocket sharks from other shark species is the presence of an internal “pocket” gland located just above each pectoral fin. The pocket opens to the outside through several slits, and its interior is lined with specialized cells. Although some scientists have speculated that these glands may secrete sex attractants (pheromones) to assist in enticing mates in the deepwater environment, anatomical studies strongly suggest that these glands produce a bioluminescent fluid, which may be used to blind and confuse predators or lure prey. The American pocket shark also possesses photophores (light-emitting organs) spread across various parts of its body.