Smithsonian National Museum of Natural History

Stygiomedusa gigantea (Browne)  Species

Remarks

“Stygiomedusa gigantea was apparently first collected in the Antarctic. Borchgrevink [1901] reported the capture of a ‘large jellyfish,’ its weight was ’90 pounds,’ ‘with arms or extremities about 12 yards long.’ An accompanying photograph, showing the distinct meshwork of anastomosing canals, leaves little doubt that the giant medusa is S. gigantea.

The second known specimen was a large (50 cm) medusa from the Southern Cross collection [Browne, 1910]. Browne thought that the specimen was fragmentary because it lacked tentacles; he noted the following morphological features: oral arms which were greater than 2 m in length, subgenital pits (small and oval), and a gastrovascular system of canals. He provisionally placed this medusa in the genus Diplulmaris.

I was kindly allowed to examine this specimen in the British Museum (Natural History) and subsequently determined that Browne’s Diplulmaris ? gigantea was, in fact, a Stygiomedusa. It was a darkly colored specimen, and although fragmentary and very brittle, there were fragments of the margin which were obviously scalloped. Other diagnostic features included portions of the oral arms that had the characteristic midrib, as well as the umbrellar cavity that contained the unique cystlike structures.

This evidence, when compared to Russell’s [1959b] original description of Stygiomedusa, reveals that Diplulmaris ? gigantea Browne and Stygiomedusa fabulosa Russell are conspecific. The valid combination is Stygiomedusa gigantea (Browne).

Stygiomedusa gigantea has been photographed in Antarctic waters at least twice. The first photographs of S. gigantea were published by Borchgrevink [1901]. The second documentation was made by J. Mead of the Smithsonian Institution, who kindly loaned me his color slides of S. gigantea photographed in situ, February 1973, Antarctic Peninsula.

Mead’s slides show a large specimen (approximately 50 cm in diameter) swimming at the surface. One of these slides shows the extremely long and folded oral arms trailing behind the medusa. The arms, about 10 m long, resemble extended, flattened rubber tubes. Underwater slides of the same specimen show a noticeably contracted umbrella, which is hat-shaped, with a high central dome and shelflike brim. Another slide clearly shows the anastomosing radial canal system peculiar to S. gigantea.”

(Larson, 1986)

Specimens