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Falling in love

Today Scott and I gathered all of our tiny Pisaster stars and assigned them to food treatments. We're not doing a feeding experiment per se but have the goal of getting these juveniles to grow, and to do that we need to figure out what they eat when they're this small. Nobody knows, or at least we haven't been able to find any literature on the subject, so we're trying a shotgun approach and offering them several different items.

One of the food items is the bryozoan Membranipora membranacea, which I wrote about yesterday. Scott picked up some fresh kelp yesterday afternoon and several of the blades were encrusted with Membranipora. We thought these new colonies might be a more appetizing meal for the stars. We knew we'd have to remove any of the Corambe slugs that might be feasting on the bryozoan, so I put a piece under the scope. And. . . whoa. . .

So lively! The bryozoan colony was unbelievably gorgeous. All of the zooids were active and reactive, with lophophores extended and tentacles flicking. This video is taken in real-time. Note how the zooids act independently, but REact as a group. They share enough neural apparatus that stimuli are perceived almost instantaneously by all the zooids in a region.

One of the things I love about colonial and clonal animals is that they upend our preconceived notions of what an individual is. In an animal like a bryozoan, what is the individual? Is it the zooid, possessing its own feeding apparatus that it employs independently from the other zooids to which it is genetically identical? Or is it the colony, consisting of many zooids? And what role does genetic identity play in the definition of individual? How much integration among units is required before they collectively form what we call a body? So many fascinating questions to ponder!

Anyway, Scott had the brilliant idea of gut-loading the bryozoans before feeding them to the stars, so I fetched a couple mL of the green alga Dunaliella tertiolecta that we have growing in pure culture and gave them a few drops, just to see what the zooids would do.


This video is also shot in real-time. The zooids are kind of just doing their thing, but when I add the drop of algae about halfway through the video they kick into high gear and go hyper. I didn't expect such an energetic response.

It is difficult to convey just how mesmerizing these bryozoans are. They are a fantastic example of animals that are completely overlooked even by many biologists because to understand and appreciate them you need to look at them under a microscope. Without magnification they really don't look like much, just whitish gray crusts growing on kelp blades. But the microscope opens up a view into their lives and shows us how complex and beautiful they are. Sometimes the most amazing and gorgeous things are the ones you can't see with the naked eye. And that is exactly what I love about them.

What do you think?

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