Casper the Deep-Sea Ghost — A Decade Since the Translucent Octopus Captivated the World

Discovery of the Deep-Sea Ghost

In 2016, NOAA's research vessel Okeanos Explorer was conducting a deep-sea survey near Necker Island in the Hawaiian archipelago when its ROV Deep Discoverer captured footage of a small, translucent octopus at 4,290 meters depth. The ghostly creature, with its pale, almost transparent body, immediately captivated the internet and was nicknamed 'Casper' after the friendly cartoon ghost.

This was the deepest recorded sighting of an incirrate octopod — a group of octopuses that lack the fin-like structures and internal shell found in their cirrate relatives.

A Decade of Mystery

Ten years after its discovery, Casper remains scientifically unnamed. No specimen has been collected for formal description, making it one of the most famous yet least understood deep-sea creatures. The octopus was observed sitting on a flat rock, apparently guarding eggs, suggesting it may use manganese nodules as nesting sites.

This behavior raises serious concerns about deep-sea mining, as manganese nodules are primary targets for mineral extraction from the ocean floor.

Unique Characteristics

Casper's most striking feature is its near-total transparency. Unlike most octopuses, it lacks chromatophores — the pigment cells that allow color changes. Its body appears almost gelatinous, an adaptation to the extreme pressures of the hadal zone.

The octopus was estimated to be about 5 centimeters in length, remarkably small for a deep-sea cephalopod.

Researcher's Perspective

This little octopus captured the world's imagination overnight. It reminds us that the deep sea still holds creatures beyond our wildest expectations.

— Michael Vecchione (NOAA, Smithsonian Institution)

What Casper Tells Us About the Deep Sea

The intersection of mining and biology — Casper's apparent use of manganese nodules for egg-laying highlights a critical conflict between deep-sea mining interests and the preservation of unknown species that depend on these geological features.

The challenge of deep-sea taxonomy — Describing a new species typically requires physical specimens. At 4,290m depth, collecting delicate organisms without damage is extraordinarily difficult, explaining why Casper remains unnamed after a decade.

Viral science communication — Casper's story demonstrates how a single compelling image from the deep sea can spark global interest in ocean exploration and conservation. The nickname alone has done more for deep-sea awareness than many formal research papers.

For more NOAA deep-sea research, see "The Deeper the Fish, the More Eel-Like."

編集部の解説 — キャスパーが教えてくれること

第一に、「名前のない生物」が示す深海探査の現状。21世紀に入って発見され、世界中で話題になり、ゲームのキャラクターにまでなったにもかかわらず、キャスパーにはまだ学名がありません。これは深海探査の最大の課題を象徴しています — 「見つけること」と「調べること」の間には、依然として大きなギャップがあるのです。ROVのカメラで観察はできても、標本を採集して分類学的に記載するには、さらに高度な技術と機会が必要です。

第二に、深海における「色素を持たない」ことの謎。キャスパーの最も特徴的な外見 — ほぼ透明な白い体 — がなぜそうなっているのかは、まだ解明されていません。深海では太陽光が届かないため、カモフラージュの必要がないとも考えられますが、多くの深海生物は赤色や黒色の色素を持っています。キャスパーの「幽霊のような白さ」は、深海の生存戦略に関する新しい問いを投げかけています。

第三に、市民科学とSNSの力。「キャスパー」という名前はSNSの視聴者が付けたもので、FathomVerseという市民科学ゲームでも最も人気のある動物に選ばれました。かつて深海生物は一部の専門家だけのものでしたが、ライブ配信やゲームを通じて、一般の人々も深海への関心を深めています。こうした「開かれた科学」の流れは、深海研究への支持と理解を広げる重要な原動力となっています。