Can you spot the strobilating polyp? It’s not hard to find, since the soon-to-be free swimming jelly (or ephyra) is orange-red in color, and will even pulse a bit before detaching!

#MedusozoaMadness

Close up of slide of jellyfish polyps, which are whiteish in color and hanging their tentacles down. In the center is an orange-red early jellyfish about to pop off of one polyp.

Okay so jellyfish often live as polyps for a while, but polyps don’t sting right?

Not so! The polyp stage also contains stinging cells, which house the venom-filled structures that give jellies their sting.

🎥 Sanderia (Amakusa jellyfish) polyps on slide.

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#MedusozoaMadness #ToxinTuesday

Love the #Hype4Hydrozoa for this lovely jelly!

This red eye jelly (Polyorchis penicillatus) is thought to be an ambush predator. The jelly will spread out its tentacles and slowly sink in the water (“sink fishing”), ensnaring any unsuspecting arthropod below.

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#MedusozoaMadness

Dead pink/purple lions mane jelly (Cyanea) washed up on rocky shoreline covered in green algae. A booted foot is shown for size (bell diameter length over 12 inches).

Several jellies can be longer and larger than humans!

Lion’s Mane Jellyfish (genus Cyanea): 3m bell diameter, 30+ m long tentacles!

📷 Washed up “small” Lion’s mane along rocky intertidal, with my boot for size.

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#MedusozoaMadness

Red eye jellyfish in a glass dish with a window backdrop. The bell is fairly transparent and covered in light green due to algae growing on the outside. The 60-80 tentacles are spread all around the bell as the jelly is slowly sinking.

“True” jellies: ~200 species
Box jellies: ~50 species
Stalked jellies: ~50 species

If you know me I am always #Hype4Hydrozoa, and lucky me Hydrozoa or “water animals” includes over 3500 species to get excited about, spanning from freshwater to the deep ocean!

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#MedusozoaMadness

Check this review on this highly unique and understudied medusozoan group to learn more: doi.org/10.1007/s12526…

#MedusozoaMadness

Stalked jellyfish seen through microscope lens, with a light green tinted body and orange Pom-pom shaped tentacle cluster on eight “arms”.

Okay “true” and “box” jellies, but stalked jellyfish?

Staurozoa includes ~50 species that have similar structures as a “typical” swimming medusa, but instead these stauromedusae attach to substrate like algae or rocks!

📷 Stalked jellyfish at Friday Harbor Labs

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#MedusozoaMadness

Evolution of box jellyfish (Cnidaria: Cubozoa), a group of highly toxic invertebrates | Proceedings of the Royal Society B: Biological Sciences Cubozoa (Cnidaria: Medusozoa) represents a small clade of approximately 50 described species, some of which cause serious human envenomations. Our understanding of the evolutionary history of Cubozoa has been limited by the lack of a sound phylogenetic ...

Want to learn more about box jellies? This review looks at how different species in this group are related and what that may mean for how various cubozoan traits evolved!

#MedusozoaMadness

doi.org/10.1098/rspb...

Full animals image of winged box jellyfish (Alatina alata) against black background. The jellyfish is translucent blue in color and longer than is wide, with a domed top. A single tentacle that is whiteish in color streams from corners of the cube shaped bell.

And box jellyfish? Seems odd…

In more ways than one! Cubozoans or box jellies have cube-shaped bells and 1 or more tentacles at each of the four “corners”. Some species are known for having complex eyes, fast swimming speeds, or potent venoms!

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#MedusozoaMadness
#ToxinTuesday

Large egg yolk jellyfish swimming in a tank. The center of the jelly is an orange-yellow color with yellow fluffy oral arms and thin, white-ish noodle-like tentacles streaming down the body. The orange center is surrounded by a slightly off white color. Very similar look to a cracked fried egg, in water.

“True jellyfish” you say?

Scyphozoa may be called true jellies since they often grow into larger jellyfish (easier to see!) in marine habitats across the world. There are ~200 described species such as moons, sea nettles, upside-downs, and egg yolk jellies!

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#MedusozoaMadness

Top down view of Sanderia medusae or jellyfish after several months of growth. About 50 jellyfish, pale to brownish-orange in color and swimming in a Pyrex dish.

Medusozoan classes includes:
• Scyphozoa (“true” jellies)
• Cubozoa (box jellies)
• Staurozoa (stalked jellies)
• Hydrozoa (water animals)

Jellyfish are found across these groups, but in some cases the jellyfish stage has been highly modified or even lost!

#MedusozoaMadness
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Close up through microscope of white-ish polyps of Sanderia malayensis and young, orange jellyfish either still attached to polyps or just detaching and swimming. Young jellyfish look like little cartoon suns in shape.

What are medusozoans anyway?

Medusa = jellyfish, or the swimming life stage present in the lineages of Medusozoa, a subphylum in Cnidaria! The jellyfish stage (typically) proceeds after the benthic polyp stage.

📷 Sanderia polyps and young jellies (ephyrae)!

#MedusozoaMadness
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Close up of oral side of moon jellyfish. Jellyfish is mostly white-clear against a dark blue background. Center (gastric cavity) contains splotches of brown red color, which are brine shrimp that have been eaten by the jellyfish.

Two moon jellyfish taken from above an open tank. The jellyfish close to the camera has food in stomach, second jellyfish is out of focus in the back corner. A bright tank light shines through a dark blue background of water.

Did someone say #MedusozoaMadness?

These moon jellies are just a few months old, but have grown fast on a steady diet of brine shrimp (Artemia sp.) or “sea monkeys.” You can see this jelly’s last meal still inside!

📷: Moon jellyfish (Aurelia coerulea), raised in @pcart.bsky.social lab.

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