Today we have a 3-minute video taken by ecologist Adam Greer and showing fascinating and complex zooplankton. The video is below, and I asked Adam to provide some additional information on this animal. Adam’s explanations are indented.
I am a zooplankton ecologist at University of Georgia. A major part of my research involves using camera systems to study the distribution and behavior of zooplankton. One zooplankton type we study is the appendicularians, which use mucous houses to feed on ocean microbes. They build and discard these houses several times per day, which can be a mechanism for moving carbon into the deep ocean. I recently put together a short video of this process, with the hope that it could help people see and appreciate that it is happening all over the world’s oceans. Appendicularians are quite fragile, and their houses are very difficult to see unless you use specialized optical techniques (the one we used in the video is called “shadowgraph imaging”).I thought maybe this could be a variation on the wildlife photos, but obviously you may want to just show actual photos. Still, I think some of your readers might think it is interesting. I did my best to explain what is going on and use kind of informal language so everyone can understand.The animal builds the (surprisingly intricate) house from a small mucous bubble then uses its tail to draw a current through the house. The water passes through a filter and then the particles get concentrated before being consumed (after going through the buccal tube). This diagram from Bochdansky and Deibel 1999 (below) is pretty helpful. The prey is very small relative to the size of the appendicularian – similar to the predator-prey size ratio of blue whales feeding on krill.
The video does not go into these mechanics since you cannot really see that amount of detail, but I simply say in the video that they create a current through the house to capture their food. Then it shows the various stages of house building.
And Adam’s video (with music), which is indeed mesmerizing and clearly explained. Stuff like this is going on all the time, but we (or at least I) didn’t know about it.
This is truly fascinating. Thanks so much to you and Adam for sharing it with us.
Just amazing!
Incredible.
I should have added that these appendicularians are our distant cousins in the phylum Chordata! They are sometimes called “larvaceans” because compared to other pelagic tunicates (e.g., salps and doliolids), they have an arrested tadpole-like larval form throughout their entire life cycle. I hope everyone enjoys the video!
It is truly amazing to be able to see things we were not even aware of–how complex and intricate the world is! Thank you for adding to our knowledge.
Fascinating! It looks like they capture the squiggly things, but not the copepods (or, at least I think they’re copepods). Maybe the copepods are strong enough to evade the suck. If they create new mucus nets several times per day, they are using quite a bit of energy to keep themselves fed. Cool video!
What the appendicularians actually capture is too small for us to image with this instrument. One pixel in the video is about 70 microns, which is larger than the microbes that the appendicularians consume. Yes, the black critters that are really abundant and hopping around are all copepods and will not be caught in the mucous houses. However, the discarded houses can stick all sorts of different dead and dying organisms together and sink rapidly to depth. The details of this topic are very interesting scientifically because of implications for making the ocean a carbon sink (net uptake of CO2).
I see. The actual prey are too small to see. (Well, maybe I don’t see. :-)) The copepods give you a sense of scale.
Absolutely facinating! I didn’t see any examples, but do the little copepods zooming about ever get caught inthe mucus filter?
Oh wait, Just ast I wrote that sentence I glanced up and saw that Norman observed the same thing.
Again, thanks for a most interesting video. There are so many wonderful, cool, and weird things in this world and I’m so grateful I get a chance to to see them virtually here at WEIT.
Fascinating, thanks for sharing. I must confess that biology/ecology isn’t an area I’ve studied at all, so had to watch and read the description a couple times to understand it all. One question I have is whether other creatures then go on to eat the appendicularians, and does that pose challenges to hoping for this process to form a potentially beneficial ocean carbon sink?
The appendicularians are so abundant – it is really difficult to overstate that. They also have many predators, such as early stage tunas https://aslopubs.onlinelibrary.wiley.com/doi/10.4319/lo.2010.55.3.0983. There are also many gelatinous animals that feed on appendicularians, but we known surprisingly little about the different types of jellies and how many are out there (mostly because they are fragile and difficult to quantify). Because the appendicularians produce several houses per day (and some must make it a few days to reproduce), I think it is safe to say that the predators are not capable of completely cutting off their house making, but we certainly need to better understand this process (and its variability) if we want to better resolve its connection to carbon flux or the ocean’s carbon sink capabilities.
Adam: Neat video and explanation! So, swimming thru the water inflates the mucus bubble? The complexities of evolution at a tiny scale!
Thank you! The swimming or head movement must inflate mucous bubble at least a little bit. The mucous bubble has to get large enough so that the animal can plug the outflow current hole with its tail. I was not able to capture that exact moment where the “shower cap” becomes just big enough to start the 2nd step.
Thanks. Some reading suggests that these little animals have only a few hundred neurons, making these little mucous traps even more impressive as examples of extended phonotypes!
Wow! I have only heard of these but have never seen them. The video is very well done. Can the microscopy use dark field, or Nomarski optics?
The problem with dark field optics is that the depth of field is relatively small, so the organism can go in and out of focus if it is moving. With the shadowgraph optics, the animals are back-lit, and the light goes through plano-convex lenses that make the light beams parallel or “collimated” before being re-focused into the camera. The apps are swimming around happily in a container that is about 2-3 cm thick. With other optical techniques, it might be easier to see some of the details on the house, but it would be more difficult to get them behaving “naturally.” There are researchers at Monterey Bay Aquarium Research Institute that have designed instruments to capture more details of the app house in the ocean (no container or tank required) https://www.nytimes.com/2020/06/05/science/ocean-biology-larvaceans-lasers.html
Just thanks and much appreciation as a biology-majored MD who misses biology like this. Endless forms most beautiful.
Encore!! I hope this is the first in a series about our little cordate cousins. Headbanging and shower caps. Very metal.
Also, what was with that zippy little Doliolid?
Thank you! Please, sir, may we have more?
This was so very cool! As an airline pilot, I’m usually focused on the very big, moving through a fluid. (Airplane through air.) I love this look at the very small, moving through a fluid.
Added to the list of
Stuff I had no idea about but am now fascinated by.
Thank you.
Fascinating, thank you so much for sharing. I so look forward to all the wildlife photos and videos.