Species spotlight: Egg Yolk Jellies

One of my favorite activities for outreach are two sheets of beautiful jellyfish photos my lab mate and I made, all with hilarious common names. Of all the different species, most folks can immediately guess the Egg-yolk Jellyfish, Phacellophora camtschatica.

P. camtschatica are true jellyfish (Class Scyphozoa, Family Ulmaridae) often confused with the Lion’s Mane’s (Family Cyaneidae). An easy way to tell the difference (at least to those keeping these animals in the lab) is by the number of lobes; P. camtschatica has 16 lobes that create 16 clusters of tentacles, compared to 8 from Lion’s Mane jellies. Egg-yolk jellies can be 60 centimeters in diameter with tentacles 3-6 meters long. These are temperate water animals that live from the Gulf of Alaska to Chile on the Eastern Pacific coast, as well as within the Atlantic and Mediterranean. And that delightful yolk-like middle of the medusa is gonadal tissue, but this color can change with their diet. Developmentally, the asexual budding when these jellies are polyps seems to be utilized for changing locations rather than making sibling neighbors, which may be important in blooming dynamics for this species. And a developmental fun fact: the buds appear at the midpoint of the stolon rather than at the tips, like that of moon jellyfish.


P. camtschatica actually host symbiotic amphipods within their bell and juvenile crabs on the outside of their bell. Even juvenile fishes can live within P. camtschatica tentacles, though it is not well understood how these animals avoid getting stung. One study found up to 326 individual crustaceans, Cancer gracilus, and 446 amphipods, Hyperia medusarum, living on one medusa. Even more fascinating, C. gracilus and H. medusarum feed off the medusa (parasitism much?), but C. gracilus larvae will eventually grow to become cleaning symbionts and consume the more problematic, i.e. host-consuming H. medusarum. Since C. gracile and other animals have been seen on other species of jellyfish medusa, the same study above wanted to determine if these animals will ride any gelatinous object. So they built a “pseudomedusa” from gelatin and nylon and released C. gracilis larvae to see if they would cling on, and they did! I love science.

But I think one of the most amazing things about these jellies is their diet: other jellyfish. That’s right, these glorious gelatinous animals survive by eating other gelatinous animals. This may begin as early as when the ephyrae are released; one laboratory observed that newly liberated ephyrae of Egg Yolks consumed the newly liberated ephyrae of Aurelia labiata. Egg yolks are actually ambush predators, spending most of their time moving vertically in the water column, though very slowly and often motionless for long periods of time. Their goal is to move up and down the in the water column and snag jellies that are moving horizontally within the current.



From a venom perspective, these animals are not wholly impressive. Though unpleasant, their sting is not truly dangerous to humans.  But that does make some inherent sense. These animals would not be that painful to us vertebrates because their venom is not made to catch and consume vertebrates. I would not be surprised if their venom has become structured specifically for digesting their gelatinous prey. Perhaps that is how these chitinase crustracean symbionts and juvenile fish have been able to survive with these animals; the venom is not really tailored to capturing and consuming them. It is also interesting to consider that these ambush predators are slow movers yet grow very large. There are a lot of metabolic considerations here that would make studying their venoms enticing. But since their venom has yet to be characterized, only time will tell.

For now, I leave you with this awesome videos of egg yolks.


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