Mystery of floating jelly balls

Jul 28, 2017 • 2:32 PM UTC

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Manu Prakash

I am a faculty at Stanford and run the Prakash Lab at Department of Bioengineering at Stanford University. Foldscope community is at the heart of our Frugal Science movement - and I can not tell you how proud I am of this community and grassroots movement. Find our work here: http://prakashlab.stanford.edu

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I am at Woods Hole this week; and just amazed with the biodiversity in the coastal environments around here. I took a stroll around Wood neck beach, with my 6 year old nephew who just got his first plankton tow.

The ocean is connected with a little stream and a current passes back and forth. Our eyes caught something strange – a centimeter scale ball of green jelly floating in the water. We saw hundreds of these balls floating. I had never seen anything like this; so we had to collect them.

The balls are almost buoyant, just floating in the ocean.

I cut one of these jelly balls in half; and found it filled with tiny little white specks.

When I cut them in half; it was filled with tiny little white dots. The outer coating is green because of a lot of algae that's growing on the surface. And an incredible variety of ciliates, nematodes and bacteria fill the outer coating.

It was now time to put this jelly inside the foldscope and see what this is. Since it was jelly like; I decided to put some spacers before imaging the same.

Here is the surprise, I saw beautiful larvae growing inside these jellies. Every single speck of dust is an individual larvae.

Another view of the larvae, with a filamentous bacteria crawling around.

The rough scale bar on these larvae is around 200 microns across.
I am currently field testing the new foldscope design with focus and field of view locking. We will soon be releasing this new design. I am very excited with how it performs in the field.
It's very clear that the larvae is ciliated. The ciliary beat is unusual. What's striking is a clear behavioral switching where the cilia fold and unfold with muscles at the base of the cilia. I think I am also seeing an eye spot. A lot of bacteria around the larvae.
Another puzzle I am wondering about is how are these larvae able to generate any thrust in this very viscous jelly. Possibly the jelly has nonlinear properties, making it possible for the larvae to escape this egg medium and not just be trapped in it forever. The jelly is quiet consistent – and does feel like a jelly fish.
I am trying to identify this larvae; so please leave a comment if you can identify the same. I had previously thought that these are egg sacs from salps, but at this point I am unsure what I am looking at. During collection, another wild guess was that this is a giant cell of "Valonia ventricosa"; but I did not see any evidence of a membrane or a cell wall. Mostly jelly.
https://en.m.wikipedia.org/wiki/Valonia_ventricosa
A fascinating observation I really liked was the ecosystem of organisms growing on the outside of the jelly balls. Clearly, a lot of stuff would like to turn this into food. Take a look for yourself, it's a jungle out there – quiet literally.
Time lapse of diatom traffic on the surface of these jellies.

Now, some of the eggs were filled with these ciliates. Clearly, the larvae make great food for the ciliates. But (as was indicated by a school teacher Simon to me, see post on crab larvae); the ciliates become food for the larvae when they grow up. Now I also understand why a larvae needs to have a egg case until it can defend itself against ciliates. Or else; everything will become food.

I still have a few jelly balls, and will try to take more data and see if I can let them grow for longer. But I would love to hear if anyone else has found these balls of floating jelly before and seen these larvae.
Until next time, keep exploring.
Cheers
Manu
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