{{Short description|Species of jellyfish}} {{Cleanup MOS|date=February 2025}} {{use dmy dates|date=March 2026}} {{Speciesbox | image = Stygiomedusa Gigantea ov.jpg | image_caption = Illustration of ''Stygiomedusa gigantea'' | genus = Stygiomedusa | parent_authority = Russell, 1959 | species = gigantea | authority = (Browne, 1910)<ref>{{cite web |editor-last=Boltovskoy |editor-first=D. |title=Marine Species Identification Portal : Stygiomedusa gigantea |publisher=Species-identification.org |url=http://species-identification.org/species.php?species_group=zsao&id=2439 |access-date=2015-08-19 |archive-url=https://web.archive.org/web/20160303215448/https://species-identification.org/species.php?species_group=zsao&id=2439 |archive-date=3 March 2016}}</ref> | synonyms = * ''Diplulmaris gigantea'' * ''Stygiomedusa fabulosa'' * ''Stygiomedusa stauchi'' }}
'''''Stygiomedusa gigantea''''',{{efn|{{etymology|grc|''Στύγιος'' (Stúgios)|Stygian,| |''Μέδουσα'' (Médousa)|Medusa,| |''γιγάντεια'' (gigánteia)|gigantic}}}} commonly known as the '''giant phantom jelly''', is the only known species in the monotypic genus of deep sea jellyfish, '''''Stygiomedusa'''''. It is in the Ulmaridae family.<ref name="BritishMuseum">{{cite book |editor-last=Bell |editor-first=F. Jeffrey |title=Cœlentera: Medusæ |series=Natural History: Voyage of the S. S. Discovery under Capt. R. F. Scott |author-first=Edward T. |author-last=Browne |chapter=Diplumaris (?) gigantea |volume=5 |pages=56-58 |location=London |publisher=Order of the Trustees of the British Museum |date=1910 |doi=10.5962/bhl.title.14923 |oclc=727233164 |url=https://www.biodiversitylibrary.org/item/51841#page/254/mode/1up |access-date=6 March 2026 |via=Biodiversity Heritage Library}}</ref> With only around 118 sightings in 110 years, it is a jellyfish that is rarely seen, but believed to be widespread throughout the world, with the exception of the Arctic Ocean.<ref name="bbc">{{Cite news|last=Bourton|first=Jody|url=http://news.bbc.co.uk/earth/hi/earth_news/newsid_8638000/8638527.stm|title=Giant deep sea jellyfish filmed in Gulf of Mexico|website=BBC - Earth News|date=2010-04-23|access-date=2019-03-17|language=en-GB}}</ref><ref>{{cite journal |last1=Benfield |first1=Mark C. |last2=Graham |first2=William M. |title=''In situ'' observations of ''Stygiomedusa gigantea'' in the Gulf of Mexico with a review of its global distribution and habitat |journal=Journal of the Marine Biological Association of the United Kingdom |date=September 2010 |volume=90 |issue=6 |pages=1079–1093 |doi=10.1017/S0025315410000536|bibcode=2010JMBUK..90.1079B |s2cid=85342580 }}</ref><ref name="mbari">{{cite web |title=Giant phantom jelly |work=MBARI |date=29 November 2021 |url=https://www.mbari.org/products/creature-feature/giant-phantom-jelly}}</ref>
The Monterey Bay Aquarium Research Institute's remotely operated underwater vehicles have only sighted the jelly 27 times in 27 years. A study conducted by the Journal of the Marine Biological Association of the United Kingdom, focusing on four ''Stygiomedusa gigantea'' present in the Gulf of Mexico, revealed information regarding the wider distribution of this species. ''S. gigantea'' is thought to be one of the largest invertebrate predators in the ecosystem.<ref name="bbc"/> It is commonly found in the ocean's midnight zone, and twilight zone usually at depths of {{convert|6665|m|ft|abbr=on}}.<ref name="mbari" />
==Description== ''S. gigantea'' has an umbrella-shaped bell that can grow up to {{cvt|1|m|ft|frac=4}}.<ref name="Drazen"/> The bell's pliant tissue allows for the jellyfish to stretch 4 to 5 times its size, presumably to engulf its prey. Their four arms have a "paddle-like" or "kite-like" shape and can grow up to {{cvt|10|m|ft}} in length. The arms grow in a "V" shape transversely,<ref name="BritishMuseum"/> with a wider base and tapering towards the ends. They do not have any stinging tentacles and instead use their arms to trap and engulf their prey which consists of plankton and small fish.<ref name="mbari"/><ref name="bbc"/> From Browne's analysis of a collected ''S. gigantea'', their jelly appears a red-orange color only when there is visible light.<ref name="BritishMuseum"/> As light does not penetrate the deep ocean where they dwell, they may appear "invisible" or glow orange very faintly in their surroundings, depending on the depth of the water.
Their bodies being made of either spongy tissue or jelly allows the species to withstand the enormous deep ocean pressure of {{cvt|5800|psi|MPa atm psi|order=out}}. The circular stomach contains canals that connect to the surface of the sub-umbrella. It is inferred that the lower stomach is thick to ensure the species has the strength to carry their long arms. Its four genital openings are also small to avoid weakening the stomach.<ref name="BritishMuseum" /> Since there are no gastric pouches nor radial canals, the jellyfish was determined to be a part of the Ulmaridae family.{{citation needed|date=April 2022}}
== Sightings == [[File:Phantom Jellyfish Off of the Melchior Islands.webm|thumb|''Stygiomedusa'' swimming near the Melchior Islands as seen from Viking submersible "Ringo" in December 2023.]] Although ''Stygiomedusa'' is not native to the Antarctic Ocean, there have been sightings of the jellyfish in the Antarctic Ocean<ref>{{Cite web |first1=Patrick |last1=Pester |date=2023-02-27 |title=Alien-like giant phantom jellyfish spotted in frigid waters off Antarctica |url=https://www.livescience.com/alien-like-giant-phantom-jellyfish-spotted-in-frigid-waters-off-antarctica#:~:text=The%20new%20study%20describes%20direct,for%20propulsion,%22%20Moore%20said. |access-date=2024-11-16 |website=livescience.com |language=en}}</ref> with the help of submersibles.
Daniel M. Moore, a marine biologist with Exeter University in the UK and chief scientist for Viking Cruises, states that the reason Antarctic waters below {{cvt|160|ft|m ft|-1|order=out}} haven't yet been well explored is that they are so difficult and expensive to reach. However, the frequent encounters with this animal are from tourism expeditions in the Antarctic that are increasingly offering personal submersibles to guests to take photos. This leads to the sighting of the giant phantom jellyfish hundreds of metres underwater off the coast of Antarctica's Rongé Island.
There have been observations of the rarely encountered ''Stygiomedusa gigantea'' at depths of {{cvt|80|-|280|m|ft}}, in the mesopelagic and lower epipelagic zones around the Antarctic Peninsula coastal waters. The Norwegian Polar Institute and an international peer-reviewed journal called Polar Research, which corresponds with Daniel M. Moore of Viking Expeditions, found ''Stygiomedusa gigantea'' in the Antarctic Peninsula at Georges Point, Rongé Island, Fournier Bay, Anvers Island, and Paradise Harbour.
Giant phantom jellyfish live in every ocean except for the Arctic Ocean. However, because they typically swim deep below the surface, they are hardly seen by humans. Daniel M. Moore noted that one potential explanation for the sightings is that the jellyfish may swim higher up to expose themselves to ultraviolet radiation, which will rid them of parasites. Another hypothesis is that the upwelling deep water found around the Antarctic continent just carries them upward.
==Behavior== Known to be one of the largest invertebrate predators in the deep sea, the giant phantom jellyfish's typical prey consists of plankton and small fish. The ''S. gigantea'' tends to be more dominant in locations with a low productivity system, which in turn deters other predatory organisms, like fish, to high productivity systems (coastal, upwelling zones). However, the jellyfish remains an important predator for the deep sea, often competing with squids and whales.<ref name="Burd">{{Cite journal |last1=Burd |first1=Brenda J |last2=Thomson |first2=Richard E |date=2000-09-01 |title=Distribution and relative importance of jellyfish in a region of hydrothermal venting |url=https://linkinghub.elsevier.com/retrieve/pii/S0967063700000042 |journal=Deep Sea Research Part I: Oceanographic Research Papers |volume=47 |issue=9 |pages=1703–1721 |doi=10.1016/S0967-0637(00)00004-2 |bibcode=2000DSRI...47.1703B |issn=0967-0637|url-access=subscription }}</ref>
Larger ''S. gigantea'' have also been observed to be in the immediate vicinity of hydrothermal vents where large proportions of zooplankton are abundant. This is in mesopelagic and bathypelagic depths. The further away from hydrothermal vents, the smaller the medusae are—indicating that zooplankton are an important resource for the species. Due to this, the medusae are well off during early spring to early summer when zooplankton biomass is enhanced.<ref name="Burd"/>
Evidence has been collected to support the first-ever documented symbiotic relationship for an ophidiiform fish, ''Thalassobathia pelagica''. Scientists have observed that the large umbrella-shaped bell of ''S. gigantea'' provides food and shelter for ''T. pelagica'', while the fish aids the giant phantom jelly by removing parasites. The ''S. gigantea''{{'}}s jelly providing shelter for ''T. pelagica'' is essential for the fish, considering the lack of shelter resources at such extreme ocean depths. Studies to further support this symbiotic relationship have shown that the two species reassociate with one another even if separated. It was inferred that ''T. pelagica'' is able to find its way back to the giant phantom jelly due to neuromasts that increase the sensitivity of low-frequency water movements—which the bell of the jellyfish emits.<ref name="Drazen">{{cite journal|last1=Drazen|first1=Jeffrey C.|last2=Robison|first2=Bruce H.|year=2004|title=Direct observations of the association between a deep-sea fish and a giant scyphomedusa|journal=Marine and Freshwater Behaviour and Physiology|volume=37|issue=3|pages=209–214|doi=10.1080/10236240400006190|bibcode=2004MFBP...37..209D |s2cid=83713836 }}</ref>
==Discovery== The first ''S. gigantea specimen'', weighing in at {{convert|90|lb|kg|-1|spell=on|order=flip}}, was collected in 1899, but it was not recognized as a species until 1959.<ref name="BritishMuseum"/> Despite having discovered only 118 individuals within 110 years (1899–2009), gelatinous mucus from the medusa have been found covering vents, indicating they may travel in swarms. Similar large jelly Schyphomedusae were observed traveling in swarms off the West coast of North America. However, there are instances in which the species is spotted alone, such as the ''S. gigantea'' identified at a depth of {{convert|1200|m|ft|abbr=on}} in the San Clemente Basin just off of California.<ref name="Burd"/>
The giant phantom jelly occurs all around the world with the exception of the Arctic Ocean. They are typically found 61°N–75°S and 135°W–153°E. In areas of high latitude in the Southern ocean, the depth at which the species may be found are at the mesopelagic and epipelagic levels. However, in areas of mid to low latitude, the species are typically found at bathypelagic and mesopelagic levels. This is due to the variability of the ocean's temperature and light distribution.{{citation needed|date=April 2022}}
==Reproduction==
Determining the reproduction of the ''S. gigantea'' is difficult considering how rare sightings are. It has been noted that young captured ''S. gigantea'' looked like an exact miniature of the adult.<ref name="BritishMuseum"/> However, researchers have analyzed the jellyfish's structure and anatomy enough to understand how it may reproduce.
The ''S. gigantea'' has four brood chambers that protrude into the stomach in folded narrow ridges and epithelium that covers the gastric side. Its lower periphery has frills along the folds, creating a band about {{cvt|20|mm|in|frac=4}} high.<ref name="Russell">{{cite journal |last1=Russell |first1=Frederick Stratten |last2=Rees |first2=William J. |title=The viviparous scyphomedusa ''Stygiomedusa fabulosa'' Russell |journal=Journal of the Marine Biological Association of the United Kingdom |volume=39 |date=1960 |pages=303-318 |url=https://plymsea.ac.uk/id/eprint/2062/1/The_viviparous_scyphomedusa_Stygiomedusa_fabulosa_Russell.pdf |access-date=6 March 2026}}</ref> Above this band, there is a germinal line that forms a shallow groove with different epithelial cells that are more cubical in shape with large, rounded nuclei.<ref name="Russell" /> Irregular placement of the cells in small pits (small clumps of cells, similar to cyst) along the germinal line produce a multiplication of epithelial cells that create a deep invagination. This is the first stage leading to the reproduction of ''S. gigantea''. The cyst grows with a pointed end on the subumbrella side. As its size increases, it pushes out the brood chamber wall and into the cavity of the chamber. Simultaneously on the opposite end, two outgrowths develop horizontally, making the cyst into a "T" shape.<ref name="Russell" /> This protrudes more and more as size increases, taking the brood chamber with it. Eventually, a thin membrane forms and the cyst enters the stomach cavity.{{citation needed|date=April 2022}}
Within the cyst, a scyphistoma—a single developing medusa—forms and is now called a chorion. Once the chorion grows into about {{val|2|u=mm}} long and {{val|2|-|3|u=mm}} in diameter with teat-shaped distal ends (which are basal outgrowths), it begins to be pushed out of the chamber. Within the chorion capsule, differentiation and formation begins. The inner epithelial wall is directly from the parent tissue and is pocketed into its distal tips that will eventually become the ''S. gigantea''{{'}}s arms. As the "baby" medusa grows, it takes the shape of the capsule.<ref name="Russell"/>
In order to escape, the well-developed "baby" medusa will detach from the subumbrella wall where it was already slightly protruding. It then exits through the gastric cavity and out the parent's mouth.<ref name="Russell"/>
The baby medusa soon become free-swimming planules, then polyps or ''scyphistomae'' that reproduce asexually through budding or podocysts. These are what become larval medusae that feed on plankton. Eventually, it will grow into the size of an adult. It is inferred that reproduction of ''S. gigantea'' is continuous with one parent estimated to produce fifty to one hundred medusa.<ref name="Russell"/>
== Notes == <references group="lower-alpha" />
==References== {{Reflist}}
==External links== *[https://www.mbari.org/products/creature-feature/giant-phantom-jelly Giant phantom jelly] - Monterey Bay Aquarium Research Institute *[https://mashable.com/video/deep-sea-ocean-sighting-phantom-jellyfish Giant, cryptic ocean dweller filmed roaming the deep sea] - "Mashable" *[https://www.youtube.com/watch?v=sLGkBnw6X6U Rare monster jellyfish caught on tape] – ''Discovery Channel'' *[https://obis.org/taxon/135311 Distribution of Stygiomedusa gigantea] – Ocean Biodiversity Information System
{{Taxonbar|from1=Q21091022|from2=Q140925}}
Category:Ulmaridae Category:Scyphozoan genera Category:Cnidarians of the Pacific Ocean Category:Cnidarians of the Caribbean Sea Category:Marine fauna of Asia Category:Marine fauna of North America Category:Marine fauna of the Gulf of California Category:Western North American coastal fauna Category:Fauna of California Category:Taxa described in 1959 Category:Monotypic Cnidaria genera