Telescope Fish live in a world of endless night. Hundreds of meters below the waves sunlight fades into shadow and the ocean becomes nearly pitch black. In this silent universe the Telescope Fish survives by turning its body into the perfect light-spotting machine.
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| Telescope Fish with tubular eyes / Image Source: Twitter |
This rare deep sea fish belong to the genus Gigantura, which includes at least two species: Gigantura indica and Gigantura chuni. They live silently in cold deep water between about 500 and 2,100 meters down. In these zones every photon counts. Their tubular, forward‐facing eyes are among the most astonishing adaptations in marine life.
Their eyes are large lenses mounted inside long cylindrical sockets. These eyes point upward when hunting silhouetted prey above them. The shape and placement gather faint light and help Telescope Fish detect bioluminescent flickers and outlines that most creatures could never see.
How Telescope Fish use their eyes to navigate darkness
Telescope Fish eyes are not like ours. They are adapted to look toward the surface to catch any light slipping down through the depths. They have less sideways vision but their view overhead can make or break a meal. Slight changes in posture let them see silhouettes of prey gliding above against the dim glow of residual light.
Their bodies are silvery and scaleless which helps them avoid detection in the dim, scattered light. Their tails are long and ribbon-like, sometimes longer than the rest of their bodies. This helps reduce drag and allows silent drifting as they wait or slowly move upward toward prey.
One of the scariest creatures in the deep-sea: Telescopefish (Gigantura chuni) pic.twitter.com/t5gJzwAjo5
— 𝕏 Ali Al Samahi 🇦🇪علي السماحي (@ali_alsama7i) September 20, 2025
Life deep under: behaviour, hunting and survival
In the mesopelagic and upper bathypelagic zones where Telescope Fish live there is little food, little heat, and constant pressure. These fish are probably solitary predators. They hunt bristlemouths, lanternfish and dragonfish, creatures that also live in dim light. By using their eyes they detect faint glows or tiny flashes of bioluminescence or even silhouettes of prey against whatever light comes from above.
They also have jaws and stomachs that stretch. If they catch prey larger than themselves, their bodies can accommodate the meal. This is a common deep-sea trick since chances to feed are rare. When opportunity knocks they must be ready.
Larvae of Telescope Fish are born in upper ocean layers where more light is present. As they grow they gradually descend into darker zones. They change in shape and physiology to cope with pressure, cold, and darkness.
Why Telescope Fish are so rare and hard to study
Because they live so deep and in remote parts of the ocean Telescope Fish are seldom seen. Most knowledge comes from nets or videos taken by deep-submersibles and remote cameras. Every new sighting is a chance to learn something important.
Scientists recently improved understanding of their eye structure and feeding behavior by studying preserved specimens and in situ video. But many mysteries remain. How exactly do they mate, where exactly do they migrate daily, how many there are—these questions are still largely unanswered.
The wonder of ocean light and why it matters
The adaptations of Telescope Fish remind us of how life finds a way even in extreme darkness. They make noise without moving, see more with less, and serve as useful indicators of deep sea ecosystem health. As ocean fronts shift, climate changes, and human activity reaches deeper, animals like Telescope Fish may help reveal how the deep seas respond.
Studying them also inspires technology. Their eye design could suggest ideas for ultra-sensitive optical sensors, underwater cameras, even deep space instruments where light is scarce.