研究團隊表示，冥河水母在1899年首次被發現，但一直到1959年科學家們才承認牠是一個新物種，且從首次發現至今，科學家們也只遇到這種巨型水母約100次，即使是現在，人類對於這種生物的了解也很少。


▲冥河水母是地球上最巨大的水母之一。

儘管冥河水母在除了北極以外的所有海域都已有發現紀錄，但由於牠們可以下降到6000公尺以上的深度，即使有無人攝影器材的幫助，也很難捕捉到牠們的身影。蒙特利灣水族館附設研究所也在聲明中提到，過去34年的海洋研究、探查中，也只有過9次目擊冥河水母的記錄。

據《國家地理》報導，冥河水母是地球上最巨大的水母之一，與其他水母不同，牠們沒有帶刺觸手，取而代之的是可以長到超過10公尺的4條帶狀「手臂」，並用這些手臂來捕捉獵物進食，雖然沒有明確證據，但海洋生物學家認為牠們以浮游生物和小魚為食。

An extraordinary deep-sea sighting: The giant phantom jelly

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This ghostly giant is a rare sight. But in November 2021, MBARI researchers spotted this giant phantom jelly (Stygiomedusa gigantea) with the ROV Doc Ricketts 990 meters (3,200 feet) deep in Monterey Bay. The bell of this deep-sea denizen is more than one meter (3.3 feet) across and trails four ribbon-like oral (or mouth) arms that can grow more than 10 meters (33 feet) in length. MBARI’s ROVs have logged thousands of dives, yet we have only seen this spectacular species nine times.

The giant phantom jelly was first collected in 1899. Since then, scientists have only encountered this animal about 100 times. It appears to have a worldwide distribution and has been recorded in all ocean basins except for the Arctic. The challenges of accessing its deep-water habitat contribute to the relative scarcity of sightings for such a large and broadly distributed species.

Historically, scientists relied on trawl nets to study deep-sea animals. These nets can be effective for studying hardy animals such as fishes, crustaceans, and squids, but jellies turn to gelatinous goo in trawl nets. The cameras on MBARI’s ROVs have allowed MBARI researchers to study these animals intact in their natural environment. High-definition—and now 4K—video of the giant phantom jelly captures stunning details about the animal’s appearance and behaviors that scientists would not have been able to see with a trawl-caught specimen.