How We Know

Creature reference

Barreleye fish

Macropinna microstoma · 600–800 m

Reference answer

A fish with tubular eyes inside a transparent, fluid-filled shield that helps it look upward and track prey.

Adaptations

  1. Rotating tubular eyes
  2. Transparent protective head shield
  3. Large fins for precise hovering

Depth zones

Twilight ZoneA dim global layer where enormous numbers of animals migrate upward at night and descend before dawn.

Evidence

Sources reviewed

  1. Researchers solve mystery of deep-sea fish with tubular eyes and transparent headMonterey Bay Aquarium Research Institute · checked 2026-07-30