Pocket Shark

Where are pocket sharks typically found in the ocean?

Information regarding the distribution of pocket sharks is limited, as the group is known from only two specimens collected in vastly different marine environments.¹

• Mollisquama parini: The first specimen, a large female, was collected in 1979 near the Nazca Ridge in the southeast Pacific Ocean.¹
• American pocket shark (M. mississippiensis): A second specimen, a juvenile male, was collected in 2010 in the northern Gulf of Mexico.¹

Both specimens were captured via mid-water trawls at depths ranging from 330 to 580 metres (approximately 1,100 to 1,900 feet), though the actual seafloor depth in these areas was significantly deeper, between 2,000 and 3,000 metres (roughly 6,600 to 9,800 feet). Because so few specimens have been studied, the full extent of their habitat remains largely unknown.¹

What is the significance of the pocket shark’s bioluminescent organs?

The bioluminescent organs of the pocket shark are considered significant for their potential roles in survival and interaction within the deep-sea environment. While some researchers have hypothesized that the internal glands located near the pectoral fins might secrete pheromones to attract mates, anatomical evidence strongly suggests these glands produce a bioluminescent fluid.¹

This light production is believed to serve several critical functions:

• Defense: The fluid may be used to blind or confuse potential predators, allowing the shark to escape.¹
• Predation: The bioluminescence may act as a lure to attract prey in the darkness of the deep ocean.¹
• General Illumination: In addition to the specialized pocket glands, the American pocket shark (M. mississippiensis) features photophores distributed across its body, which may assist in navigating or signaling in its lightless habitat.¹

These adaptations are consistent with the broader role of bioluminescence in marine life, where light is frequently used for protection, species recognition, and hunting.²

How rare are pocket sharks, and when was the species first discovered?

Pocket sharks are exceptionally rare, as the entire genus is known from only two specimens collected decades apart.¹

The first discovery occurred in 1979, when a large female specimen of Mollisquama parini was collected near the Nazca Ridge in the southeast Pacific Ocean; this species was formally described in 1984. The second specimen, a juvenile male, was collected in the northern Gulf of Mexico in 2010. While this second specimen was described in 2015, it was not until 2019 that it was formally classified as a distinct species, the American pocket shark (M. mississippiensis).¹

Because only these two individuals have ever been studied, our understanding of their population size, distribution, and natural history remains extremely limited.¹

What other unusual shark species are closely related to the pocket shark?

The pocket shark (genus Mollisquama) is classified within the family Dalatiidae, making it most closely related to other deepwater species within that group. Notable relatives include:

• Kitefin sharks (Dalatias licha): These are considered the pocket shark’s closest relatives within the Dalatiidae family.¹
• Cookie-cutter sharks (Isistius): Known for their unique feeding habits, these are among the best-known relatives of the pocket shark.¹
• Pygmy shark (Euprotomicrus bispinatus): This species is also a close relative and ranks among the smallest shark species currently known to science.¹

Like the pocket shark, these species are typically found in deepwater environments and share similar evolutionary lineages within their family.¹