Pelagothuria natatrix
The only known truly pelagic sea cucumber, resembling a jellyfish.
Pelagothuria natatrix is a species of sea cucumber in the family Pelagothuriidae, and the only species in the genus Pelagothuria. It is notable for being the only true pelagic holothurian (and even echinoderm) known to date, and for its unusual appearance resembling a jellyfish.
Quick Facts
- Taxon
- Pelagothuria natatrix
Facts from the source article.
Lore & Background
Pelagothuria natatrix was described by Hubert Jacob Ludwig in 1893 based on trawled specimens collected in 1891 by the USS Albatross between the Gulf of Panama and the Galápagos Islands at depths of 605–3,350 m. The species is extremely rare but has a very wide geographic range, having been collected in the Atlantic, Pacific, and Indian Oceans. Its appearance is unusual: it has a large umbrella-like swimming structure supported by a ring of around 12 highly modified oral tentacles, a small tapered body, and swims with the mouth on top. The body is translucent with pale purple pigmentation, and the mouth is surrounded by about 15 short feeding tentacles. The veil can be contracted like a jellyfish's and is interrupted at the central ventral radius. The animal reaches around 16 cm in total diameter. Its swimming is mostly passive, more like slightly controlled drifting.
Reader's Guide
The first in situ footage of Pelagothuria natatrix was obtained in 1989 during a scientific expedition in the Galapagos at 542 m depth off San Cristóbal Island, followed by a scientific review of deep-sea swimming sea cucumbers by John Miller and David Pawson in 1990. In 2011, the American scientific expedition NOAAS Okeanos Explorer photographed what scientists first believed to be an unknown jellyfish, but the picture was formally identified in 2014 by Smithsonian Institution experts Christopher Mah and David Pawson as Pelagothuria natatrix. A second observation was made in March 2017 by the same mission off the Samoa Islands at 443 m depth near Howland Island, identified by NOAA expert Steve Auscavitch, and included high-resolution video of the animal swimming. Since then, more attention has been brought to this unusual species, and it has been observed more than 100 times by NOAA. Its significance lies in being the only known truly pelagic holothurian and echinoderm, challenging typical notions of sea cucumber ecology and morphology.
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