#semaeostomeae

[snototter]

A pink lions mane jellyfish (Cyanea capillata) in the White Sea

by Alexander Semenov

[uncharismatic-fauna]

Uncharismatic Fact of the Day

Even though Spongebob has a fun time jellyfishing, you probably wouldn't want to mess with the real thing. The famous cartoon jellyfish are based on a real species, commonly known as the mauve stinger. Just like its fictional counterpart, mauve stingers are bright pink with vivid spots-- and they have a very painful sting!

(Image: A mauve stinger (Pelagia noctiluca) by Stergios Vasilis

[bestanimal]

Round 3 - Scyphozoa - Semaeostomeae

(Sources - 1, 2, 3, 4)

Order: Semaeostomeae

Common Name: “flag-mouth jellies”

Families: 5 - Cyaneidae, Drymonematidae (“pink meanies”), Pelagiidae, Phacellophoridae (“egg-yolk jellies”), and Ulmaridae

Anatomy: characterized by four long, frilly oral arms surrounding a quadrate mouth; tentacles line the domed bell; gastrovascular system consists of four unbranched pouches radiating outwards from the central stomach

Diet: zooplankton, crustaceans, and fish

Habitat: oceans worldwide; some species may enter brackish or even fresh water

Evolved in: Cambrian

Do you have a favorite in Semaeostomeae?

One or more of my favorite animals is in Semaeostomeae

I love at least one or more of these animals

I like at least one or more of these animals

I am neutral about at least one or more of these animals

I dislike all of these animals

Voting ended onNov 15, 2025

Propaganda under the cut:

The Lion’s Mane Jelly (Cyanea capillata) (image 3) is one of the largest jellyfish, with the largest recorded specimen having a bell width of 210 cm (7 ft) and tentacles around 36.6 m (120 ft) long.

While most jellies are exclusively marine, the Bay Nettle (Chrysaora chesapeakei) ventures into the Chesapeake Bay’s brackish water all the way up into the freshwater of Baltimore’s Inner Harbor.

The Giant Phantom Jelly (Stygiomedusa gigantea) (image 4) is a deep sea jellyfish that is rarely seen, with only around 110 sightings in 110 years. It thought to be one of the largest invertebrate predators of the ocean's midnight zone and twilight zone, with an umbrella-shaped bell that can grow up to 1 m (3.3 ft) in diameter and paddle-like arms that can grow up to 10 m (33 ft) in length. The bell's pliant tissue allows for the jellyfish to stretch 4 to 5 times its size, presumably to engulf their prey. 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. The Giant Phantom Jelly has a symbiotic relationship with the Pelagic Brotula (Thalassobathia pelagica), for which it provides food and shelter beneath its massive billowing bell, while the fish aids the jelly by removing parasites.

The Mauve Stinger (Pelagia noctiluca) is a fairly small purple jellyfish that is able to bioluminesce. Light is emitted in the form of flashes when the medusa is stimulated by turbulence created by waves or by a ship's motion. Unusually among cnidarians, Mauve Stingers are able to consume phytoplankton, alongside copepods and other usual planktonic fare.

The Moon Jelly (Aurelia aurita) (see gif above) is gaining popularity in aquarium touchtanks as they lack long tentacles and their sting has little to no affect on humans. They are also one of the longer-lived jellyfish, living up to two years in their medusa form, and are easy to rear and feed, making them a good candidate for giving humans an up-close learning experience with jellies. Fun fact: my dad let me watch The Sphere (1998) when I was 7 and it gave me Scyphophobia, a fear of jellyfish, that lasted for several years. I knew the behavior of the jellyfish as depicted in the movie wasn’t real, but I still wouldn’t enter the ocean for the next 5 years, and when I did start entering the ocean again every time I saw a jellyfish I would get out and not go back in again for another full year. It took a touch tank and several positive experiences with some Moon Jellies to get over my fear, and now I would say I’m fully recovered!

[dailybugfacts]

Do jellyfish count as bugs? If so, may I please have a jellyfish fact?

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TODAY'S FACT IS

Did you know that the Purple- Striped Jellyfish (Chrysaora colorata) is a jellyfish found off the coast of California? These respectably large jellies (the bell reaches up to 70cm in diameter) have been used as living homes for different types of crabs, which help protect and clean the jelly in exchange for shelter and transportation.

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Photo by Monterey Bay Aquarium

[saritawolf]

Pacific Sea Nettles (Chrysaora fuscescens) - (c) SaritaWolf - please do not repost

[wikipediapictures]

Aurelia aurita

“Three moon jellyfishes (Aurelia aurita) captured by a lion's mane jellyfish (Cyanea capillata) in Rågårdsdal, Lysekil Municipality, Sweden. In spring when the lion's manes are new and growing, they are voracious. You often see them catch 2-4 moon jellies and feed on them one by one. The lion's manes seem to favor attaching themselves to the underside of the moon jellies when they feed on them. These jellyfishes are about 12 cm (4.7 in) each in diameter. Photo taken shortly after the rain from a jetty in a shadowy and deep part of the fjord, with the sun just glancing in from the side.” - via Wikimedia Commons

[have-you-seen-this-animal]

Fried egg jellyfish :3

Have you seen the fried egg jellyfish (Phacellophora camtschatica)?

I have now

Yes, in photos/videos

Yes, irl

I'm not sure

Voting ended onNov 7, 2024

Photos thanks to Karolle Wall & Kevin Lee, respectively. Cotylorhiza tuberculata, the Mediterranean jellyfish, is another species which is commonly called the fried egg jellyfish :)

[alphynix]

Cambrian Explosion Month #06: Phylum Cnidaria – Medusozoa

 The medusozoans are a group of cnidarians that includes modern true jellyfish, box jellyfish, stalked jellyfish, hydrozoans, and the weird fish egg parasite Polypodium.

Due to their soft gelatinous bodies their fossil record is very sparse. While vague fossilized blobs tend get interpreted as jellyfish fairly often, many of them turn out to be trace fossils or inorganic structures, and definite preserved medusae are only found in a few sites of exceptional preservation.

Among those rare examples of fossil jellies there are some amazingly well-preserved specimens known from the mid-Cambrian, discovered in the Marjum Formation in Utah, USA (~505 million years ago).

None of these species have been given their own names, and they're all tiny, only around 1cm in diameter (0.4"). But their anatomy is still preserved in enough detail to tentatively classify them into known lineages, including the box jelly, narcomedusan, and semaeostomean shown here.

Much larger Cambrian jellyfish have been also found in Death Valley, California, and in Wisconscin, representing preserved mass stranding events on ancient shorelines. Some of these jellies were up to about 50cm in diameter (20"), indicating that large soft-bodied animals were much more common in Cambrian seas than previously thought.

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