Sloane's Viperfish

About Sloane's Viperfish

Like many inhabitants of the deep sea, Sloane’s viperfish sport light-producing organs called photophores along its belly. These flashing blue-green or yellow lights might attract tasty snacks, but they’re most useful for masking the fish’s silhouette from predators below. They’re also useful for grabbing a meal: when prey comes near, the viperfish drops a glowing light on its dorsal fin ray like a fishing lure in front of its mouth and—snap! A muscular jaw filled with clear, sharp teeth comes crashing down like a trap. Lucky for the viperfish, its first vertebra has evolved to act as a shock absorber for that powerful bite.

While a majority of Sloane’s viperfish join their neighbors on their nightly migration to the surface, scientists found that a significant number may take the night off and remain in depths ranging from 200 to 1,000 meters (656-3,280 feet), likely because they’re still full from feeding the night before. As it hunts, the viperfish stays motionless, saving energy, with its disturbingly long fangs agape. When another fish happens to swim by, portion size isn’t a concern. The Sloane’s viperfish simply unhinges its skull, opens its jaw up to 90 degrees, and expands its stomach to swallow prey, which can be 20% to over 50% larger than itself.

Based on the stomach contents of captured fish, the viperfish’s favorite meal is lanternfish, but it isn’t too discerning. Scientists have also found algae, fish eggs, and small crustaceans in viperfish specimens. After a meal, the Sloane’s viperfish can go for days without eating again. In the ocean twilight zone, it’s feast or famine—and this ferocious fish is prepared for both.

Quick Facts

Common NameSloane’s viperfish
Scientific NameChauliodus sloani
Other NamesManylight viperfish, Dannevig's Dragonfish, Sloan's fangfish
Size6-26 cm (2-10 inches)
DiscoveryMarcus Elieser Bloch and Johann Gottlob Schneider, 1801
Eats what?Lanternfish, bristlemouths, small crustaceans
Eats how?Lures prey with its flashing light, then pierces it with fangs
Is eaten by?Atlantic Bluefin tuna, pygmy sperm whale, Gervais’ beaked whale, dolphins
BioluminescenceYes, along its belly