I would like to start today's post with a breath-taking video I just saw, filmed by the on-going EV Nautilus expedition. If this is your first time you hear of EV Nautilus, I highly suggest you to have a look at their official website and their youtube channel as they have some really cool stuff going.
Ok, now to the video:
If you actually watched the video and didn't just scroll all the way down to comment "nice post" then you learned that this weird balloon alien-like thing is actually a deep sea jelly known as "Deepstaria", probably from the Deepstaria Enigmatica species.
Deepstaria is a poorly understood genus of true jellyfish known for their thin, sheet-like bodies. As of today, we know of the existence of 2 Deepstaria species:
- Deepstaria enigmatica, first described in 1967
- Deepstaria reticulum, first described in 1988
Naming
In case you wonder, the genus name "Deepstaria" originates from the "Deep Star 4000" vessel which was the first to collect a Deepstaria specimen. Deep Star 4000 was a deep submergence vehicle designed by Jacques Cousteau, built in 1965 and retired in 1972, and if you want you can click here to learn about it's history and journeys.
The specific epithet "enigmatica" is from the greek word "αίνιγμα" which translates to "riddle". That particular species was named this way because the holotype examined by F. S. Russel gave him a really hard time classifying the creature under a specific order:
"Until a more complete specimen of this medusa is obtained it is not possible to place it either in the Semaeostomeae or the Rhizostomeae, and its systematic position must remain uncertain. For this reason I name it Deepstaria enigmatica gen.nov., sp.nov., in recognition of its capture by Deepstar and its uncertain systematic position. " [1]
As for the specific epither ""reticulum" it's a latin word that translates to a small net, mesh-work bag, or purse. It's a reference both to "the anastomosing network of canals in the umbrella, and the habit of the medusa of pursing shut like a drawstring bag." [2]
Where Can I Find One?
Well, that's a tough question. Sightings of both species are extremely rare and their exact distribution range is unknown. For example, sightings of Deepstaria enigmatica have occurred from the Gulf of Mexico to the Indian Ocean to the Southern Ocean at depths ranging from approximately 800 to up to 2600m deep. There are indications that this might be actually a cosmopolitan species.
The distribution of D. reticulum includes the Eastern Central Pacific and Western Central Atlantic, USA and Bermuda and it has been spotted in depths ranging from approximately 600 to 915 m deep.
TL;DR: Unless you own a submarine or something chances are you will never encounter an individual in its natural habitat. So, if it gives you the creeps you have nothing to worry about :D
Physical Description
While most jellies have a "normal" sized bell and relatively long tentacles, deepstaria jellies have a really, really big bell and no tentacles. The two species look quite similar, with the main difference being that D. reticulum is slightly purple (while D. enigmatica is white) and has a bell that is spread wide, like a thin, translucent bed sheet.
Both species can reach lengths up to 1 meter long. If you take a good look in the first video, you might notice that the body of the creature is run by a mesh, hexagonical kind of structure. These lines actually carry the nutrients from the stomach to the jelly's body.
But why have these jellies evolved to have such a huge bell? Here's the thing. Food in the deep depths they inhabit is rare. Extremely rare! So over the course of time their bells grew larger and larger and essentially evolved into a trap mechanism that captures anything that falls into it. Any unlucky creature that ends up in the bell eventually find itself trapped in a continuously shrinking space.
Naturally, at some point it will bump into the interior "wall"s which are covered with stinging nematocysts that cause paralysis and possibly death. Soon muscular contractions bring the prey into the stomach where it meets its maker!
Their huge and shaggy bell results in them being really bad swimmers. Yes, they are capable of muscle contractions like regular jellyfish but the result is...awkard at best. But to be fair, in the depths they inhabit being a good swimmer is not something really useful. Food is scarce and conserving every last bit of energy comes first!
Diet
Although the exact details are not known, their diet is believed to consist of detritus and small roaming animals like fish.
Reproduction
Again, their reproductive habits are largely a mystery. However, since they are true jellyfish (Scyphozoa) chances are they are gonochorists, with separate male and female individuals and their life cycle going something like this:
- Egg is laid by an adult female
- After fertilization it develops into a free-living planula
- The free-living planula transforms to a scyphistoma
- Scyphistomato transforms to a Strobila
- Strobila transforms to a free-living young medusa
The End
If we exclude some boring technical details, this is pretty much all we know about these truly amazing creatures. Unfortunately, sightings are extremely rare and we can learn only so much by them. Furthermore, their deep sea environment makes specimen collection tricky and as a result most of the papers published were based on badly damaged and/or incomplete specimens.
Hopefully, one day we will learn more about these elusive creatures. In the meantime, you can check the videos to have an extra look on these magnificent creatures. The footage is not as amazing as in the first video but still quite mind-blowing I think!
Oh yeah, you can also check the references down below to learn more about them :)
By the way, if you haven't, please check my post from yesterday. As 
More Videos
References & Further Reading
1. Russell, F. S. (1967). "On a Remarkable New Scyphomedusan". Journal of the Marine Biological Association of the United Kingdom. 47 (3): 469–473. doi:10.1017/S0025315400035098
2. Larson, R. J.; Madin, L. P.; Harbison, G. R. (1988). "In Situ Observations of Deepwater Medusae in the Genus Deepstaria, with a Description of D. Reticulum, Sp. Nov". Journal of the Marine Biological Association of the United Kingdom. 68 (4): 689–699. doi:10.1017/S0025315400028800
3. Wikipedia contributors, 'Deepstaria reticulum', Wikipedia, The Free Encyclopedia, 14 January 2018, 00:49 UTC, <https://en.wikipedia.org/w/index.php?title=Deepstaria_reticulum&oldid=820276870> [accessed 19 March 2018]
4. Wikipedia contributors, 'Deepstaria', Wikipedia, The Free Encyclopedia, 16 February 2018, 01:25 UTC, <https://en.wikipedia.org/w/index.php?title=Deepstaria&oldid=825894673> [accessed 19 March 2018]
5. Wikipedia contributors, 'Deepstaria enigmatica', Wikipedia, The Free Encyclopedia, 19 February 2018, 17:55 UTC, <https://en.wikipedia.org/w/index.php?title=Deepstaria_enigmatica&oldid=826533267> [accessed 19 March 2018]
6. McClain, Craig (May 9, 2012). "Solving the Mystery of the Placental Jellyfish"