Donate Take Action

Join us


Marine Animal Encyclopedia

Stoplight Loosejaw Malacosteus niger

Like many other deep-sea fish, the stoplight loosejaw is black, relatively small, and has a large mouth. However, it is unique in that it has no floor to its mouth, hence its name. Instead, a ribbon of muscle that joins the gill basket and the lower jaw contracts to shut the mouth. This arrangement may allow the fish a wider gape and a faster strike at prey. This fish is also a specialist in light production. It has two large photophores under each eye, one that produces normal blue-green bioluminescence and the other red. No natural red light reaches these depths, so most deep-sea creatures cannot see it. The red bioluminescence reflects well off a red animal, such as a shrimp, but the shrimp will be unaware that it has been spotlighted.

Stoplight Loosejaw habitat mapzoom image
  • Order Stomiiformes
  • Length Up to 9 in (24 cm)
  • Weight Not recorded
  • Depth 3,300–13,000 ft (1,000–4,000 m)
  • Distribution Deep tropical and temperate waters worldwide