What are these clear jelly blobs on the beach?

The Question: We found clear jelly like blobs washed up along the ocean beach. They look like they could be jellyfish without tentacles. I stepped on one by mistake and it did not hurt. What are these?

Submitted by: Sheri, Rhode Island, USA

(click on photos and graphics to expand)

Aurelia labiata
Aurelia labiata

The Short Answer: Sheri, what you are describing sounds like the remains of jellyfish, probably moon jellies (this includes several species in the genus Aurelia).  (see this post for a different possibility) People report seeing these jelly discs on beaches all over the world. David Albert, professor emeritus at the University of British Columbia, has studied Aurelia labiata, the moon jelly that is common on the west coast of North America (Aurelia aurita is the east coast version). He says that what you are seeing is the “mesoglea” of the jellyfish.

moon jelly anatomy
(1) stomach (2) tentacles (3) oral arm (4) mesoglea (5) gonads (6) endoderm (7) mouth

The mesoglea is a stiffer layer of jelly that provides structure to the moon jelly. So when you find one on the beach, you are essentially finding the skeletal remains of a dead jellyfish.

Live moon jellies don’t generally cause a sting that you would notice, and once they die, the hundreds of tiny tentacles fall away pretty quickly, so as you discovered, you don’t have much to worry about in picking up a moon jelly disk. That is not true of all dead jellyfish, however, so you should be a little cautious.

I wrote previously about moon jellyfish at http://askanaturalist.com/where-did-all-these-jellyfish-come-from/

Stranded moon jelly

How do They Get on the Beach?:
A moon jelly doesn’t want to be on the beach, of course. But although they can swim by pulsing their bell to push themselves through the water, they’re not exactly strong swimmers. By angling in one direction or another, they get some directional control, but for the most part, they can swim up and float down. So it seems like it might be pretty easy for a moon jelly to end up on the sand, doomed to disintegrate and be picked up by beach goers. It turns out, however, that moon jellies have behaviors that almost always keep them off the beach.

Dr. Albert has studied the behavior of moon jellies and has found that while they normally keep themselves a meter or two (about six feet) away from the surface of the water, if they bump into or sense the bottom in shallow water, they swim up and stay near the surface for some period of time. Why would they do that?

When waves break in shallow water and then recede, the overall flow of water is shoreward at the bottom and seaward at the surface. That seaward flow at the surface is called an ebb flow. When moon jellies reverse their normal behavior in shallow water to position themselves near the surface, they place themselves in that ebb flow and get carried out into deeper water.


This doesn’t always work, of course. Dr. Albert says, “Moon jellies have behaviours that help them avoid stranding. However, jellies are primitive animals. Their behaviour has to be looked at statistically. The behaviours don’t always occur at the optimum time . For example, in some jellies, swimming toward the surface doesn’t occur until the water has become quite shallow. In that case, the ebb stream may no longer be very strong and it may be very thin. So, a jelly may be less likely to drift out of a shallow area and less likley to avoid stranding. Also, if there is a wind pushing them toward a shore on an ebb tide, they may become stranded.   The ebb tide will serve to help them drift away from the beaches, but the wind initiated currents may be stronger.”

Still, despite these occasions when the normal behavior doesn’t work, Dr. Albert asserts that the vast majority of moon jellies don’t become stranded. He says the ones that end up as mesoglea disks on the sand were probably dead before they washed ashore.

A Little Jellyfish Anatomy: What looks like a simple blob of jelly is actually a fairly complex blob of jelly. Surrounding the mesoglea disk are layers of tissue that contain channels to move tiny particles of food from the edge of the jellyfish bell to the center, where its mouth and stomach are. When you see a live moon jelly, you’ll also notice four prominent horseshoe-shaped objects. These are the moon jelly’s gonads, where it produces eggs or sperm. When you find a dead moon jelly on the beach, you may see a blob that is 25-40 cm (10-16 in.) wide, and includes the four horseshoe shaped gonads. That would represent a fairly intact adult moon jelly. As it becomes more and more degraded by wave action and decay, all that’s left is the tougher center of the mesoglea disk, which might be as little as 7 cm (2.5 in.).

What Does a Jellyfish Think About: Dr. Albert is a behavioral neuroscientist, so his interest in moon jellies isn’t really in how they end up on beaches. He is fascinated by the fact that a moon jelly can exhibit true behaviors, even though it has a nervous system that doesn’t look anything like what we think of as a brain. There is no central mass of nervous tissue in the head of a moon jelly. A moon jelly doesn’t even have a head. It’s “brain” is spread throughout the organism. Yet it changes its swimming behavior and direction in response to complex sensory information that includes temperature, salinity, touch, and light levels. Somehow, without having what we think of as a brain, it coordinates this information from the various parts of its body and “decides” on a response.

These are not simple reflexes, like when your hand jerks back in response to heat. This is more like you lying in the hot sun and deciding, “I’m getting hot, I should go be in the shade.”

No one is suggesting that a moon jelly “thinks” the way we do. But it seems to take in sensory data and then change its behavior over a period of time, which suggests some kind of processing. Jellyfish have been around for about 500 million years. Far longer than us and even longer than dinosaurs. In fact, if longevity is the measure, then jellyfish are one of nature’s big success. Dr. Albert’s hope is that by studying the simple behaviors of an animal that was “thinking” long before we were, we can gain insight into how all animal brains work.

moon jellies
Aurelia aurita

Jelly and Peanut Butter: If you search online for “moon jellies on a beach,” you’ll find other sites that show pictures and if you look at the comments, you’ll see numerous jokes about jellyfish washing ashore in their desperation to find peanut butter. On one of the sites I came across, someone called OceanDreamer went one step further:

“My intuition tells me that thousands of jelly fish came ashore searching for peanut butter fish. They combine for a tasty treat because of the sand-which-is there.”

I should probably turn off the comments on this article to avoid jelly and peanut butter jokes, but I kind of like them.

Sources: Albert, D J. (2014). Field observations of four aurelia labiata jellyfish behaviours: Swimming down in response to low salinity pre-empted swimming up in response to touch, but animal and plant materials were captured equally. Hydrobiologia, 736(1), 61-72.

Albert, D J. (2011). What. Neuroscience & biobehavioral reviews, 35(3), 474-82.

Cite this article as: Pelletier, TC. (September 1, 2014). What are these clear jelly blobs on the beach? Retrieved from http://askanaturalist.com/what-are-these-clear-jelly-blobs-on-the-beach/ on July 3, 2020.

20 thoughts on “What are these clear jelly blobs on the beach?”

  1. Thanks for all the great info. I’m learning this about Cnidarians in my Biodiversity class, and I just happened to see some at my local beach recently!

  2. went to Daytona Beach for the day, and the shore was full of these Jelly blubs. I asked people and everyone had a different story to tell what they where. Thanks for the info
    but I had never seen them there before and now there’s just too many. Something is wrong when they are so many dying.

  3. Found a ton of these this week at Flagler Beach, Fl. This is the first year I’ve seen them there. They just kept washing up. Hope the jellies in that area are doing ok

  4. This is the first time my family and I have come to our beach house in Palm coast, FL and have seen ” blobs of jelly” washed up on the beach and there are tons of them.

  5. Hi Tamberam, thanks for joining the discussion. You’re right, if the blobs are crescent shaped, they might well be snail egg masses. But if they’re fully round, they’re probably moon jellies.

  6. It’s sad that they were dead but I still think the moon jellies are SO beautiful with their gonads they resembled sand dollars on the beach. I had hoped they were alive becaue there was still water and the gonads were in tact in fact even these yellowish colored appendages were attached so they must have been recently stranded in the Baltics-at Vecaki beach near Riga. I was kind of hoping they were resting or avoiding a storm. The last thing I wanted was to hear they were dead from being stranded. But thankyou for explaining it appears I was the only one who cared whether they were dead or alive-a lot of unintelligent people in the world with NO interest in Natural phenomena.

  7. So Tom, I’m curious now. I’ve seen these wash up on the barrier islands along the Delmarva peninsula for years now. At least a decade, maybe two. Always in the warm currents in August in the past – to the point it’s awkward to swim because despite it being an ocean they’re everywhere and you have to go way, way beyond the breakers to get past them (and by going through them bleh… one or two bumping me fine, but these are denser than a kelp forest).

    Is this just part of their life and death cycle? I’m less alarmed than some because they’ve been a fact of life at local beaches and when I worked for a coastal non-profit I was used to them after a lifetime of trips to the northern “rugged” Assateague beaches. Or is the fact they arrive en masse and, well, dead seasonally a harbinger of issues and we’ve just seen it for longer in the mid-Atlantic. I should note they aren’t there for long. Maybe a week at most? Then by late August they’re generally gone. The warmest waters of September, I’ve yet to see them.

  8. Is there anything you can wear to avoid serious jellyfish stings? I went to North Carolina and my brother got stung once by a moon jelly or something small, but is there like a sun screen with something in it to dull the pain of jelly stings?

  9. Hi Laycie,

    There are at least two sun screens that claim to prevent jellyfish stings, one is Life Systems Active Factor and the other is called Safe Sea. Both are sold online and probably in stores near beaches. I have not tried either of them, so I can’t really endorse them, but you could try them. Others say that pantyhose or leggings will protect your legs. Certainly a wetsuit will protect stings, at least where it covers your skin. Tom

  10. I found a blue jellyfish and it was a live but when I pick it up to put back in the water all the legs fell off. Why?

    Also my dad thought it was fun to hit me in the face with it legs. It like thousand of needles going’s in and out of you face. Luckily it wasn’t is venoms.

  11. Thank you! I shared this jellyfish description on local Facebook social media after Moon jellies washed up by the dozens yesterday (5/25/18) on the beach in Cambria, CA.
    I posted photos of them too. What fascinating creatures they are!

    I’ll bet reducing plastic pollution of the ocean will help them keep their sense of direction.

  12. Saw some at Morro bay, CA while walking with my sister, it was dark and she stepped on one, it freaked her out…….harmless.

  13. I discovered these creatures at Koh Larn Beach in Thailand. They kept bumping into me as I swam. I have to admit, it freaked me out a little so I had to look them up to find out what they were. Glad I found your article to learn more about them. Thanks.

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