Nov 243 min read

The Barreleye Fish Is The Most Bizarre Sea Creature

Barreleye Fish

The barreleye fish, also known as Macropinna microstoma, is a fascinating and unusual deep-sea fish known for its unique, transparent head. Found in the deep, dark waters of the Pacific Ocean, this small fish has developed remarkable adaptations for survival in its harsh environment. One of the most striking features of the barreleye fish is its tubular eyes, which are encased in a transparent, fluid-filled dome on top of its head. This allows the fish to see in multiple directions—often upward to spot prey silhouetted against faint light from above, and forward when needed. Its tubular eyes are highly sensitive to light, helping it detect prey in the near-total darkness of the deep sea. With its otherworldly appearance and specialized adaptations, the barreleye fish provides scientists with a unique glimpse into the evolutionary marvels that occur in the planet’s least explored habitats.

KEY FACTS:

Found at Extreme Depths: The barreleye fish inhabits depths between 2,000 and 2,600 feet (600 to 800 meters), where sunlight barely penetrates. This environment is incredibly challenging, with high pressure, low temperatures, and limited light—all of which the barreleye has evolved to handle.

Elusive and Rarely Seen: Barreleye fish are extremely rare and difficult to observe in their natural habitat. Their discovery dates back to 1939, but because of the depth they live at, they were mostly known from dead specimens caught in nets until recent submersible explorations captured live images.

Eerie, Alien-like Appearance: With its translucent head, glowing green eyes, and small, almost finless body, the barreleye fish has an appearance that many describe as “alien-like.” This strange look is a product of unique evolutionary adaptations to life in the deep sea.

Transparent Head: The barreleye fish’s entire forehead is transparent, allowing us to see right into its skull. This clear dome, filled with fluid, protects its eyes and lets them rotate freely within the head, an adaptation for spotting prey above it in the dark, deep-sea environment.

Tubular Eyes: Unlike most fish, the barreleye has tube-shaped eyes designed to capture as much light as possible. These eyes give the fish incredible vision in the low-light depths of the ocean. Originally, scientists thought these eyes were fixed and only looked upward, but recent studies show they can rotate forward to focus on prey directly.

Light-Sensitive Eyes: Its eyes are incredibly light-sensitive, allowing it to detect the faintest of bioluminescent glows, which are common among deep-sea organisms. This helps it spot potential prey or predators in near-total darkness.

Honorable Mentions:

Anglerfish are known for their bioluminescent lure, which dangles in front of their sharp-toothed mouth to attract prey in the dark depths. The females can grow quite large and are equipped with this “fishing rod” that lights up due to bacteria, creating an eerie glow in the blackness. The males are much smaller and latch onto females for life, in some species, fusing with her body.

The gulper eel, or pelican eel, is known for its enormous, expandable mouth, which looks almost too big for its body. This oversized jaw allows it to swallow prey larger than itself whole, helping it survive in a food-scarce environment. When threatened or disturbed, the gulper eel can inflate its mouth, which creates an intimidating silhouette to ward off predators.

The giant isopod is an oversized, deep-sea relatives of shrimp and crabs look like giant pill bugs. Giant isopods are scavengers and have adapted to feast on dead creatures that drift to the seafloor. Their armored, segmented bodies and antennae give them an eerie, prehistoric look.