Sorry for the long delay in posting. I am currently taking the Embryology course at the Marine Biological Laboratory. Actually, I’ve been here since the beginning of June, but the work schedule has made it difficult to get any of these blog posts up. Every day we begin with lectures around 9am, and we often do laboratory work well past 1 or 2 in the morning!
However, I have been asked to share my experiences with The Node, a blog run by The Company of Biologists, which runs a number of important journals, including Development and The Journal of Experimental Biology. It’s a great incentive to get these posts out, despite the lack of free time. But we’re half way done with the course, so I’ll have a lot of catching up to do.
On June 7th, Nicole King from Berkeley came to teach us how to work with choanoflagellates and sponges. I have gotten to spend time with Nicole previously because we work on the same NASA astrobiology grant (which you can find more about here or here) , but this was my first chance to get some hands-on work with her model systems.
Nicole focuses on sponges and choanoflagellates to learn more about the early evolution of animals. Choanoflagellates are not actually animals, but DNA evidence suggests that they are the animals’ closest living relatives (e.g. King et al 2008). An individual choanoflegellate is made up of a single cell. It has a long flagellum, which it uses to swim through the water and to trap bacteria (which it eats) in a collar made up of microvilli. Below is a diagram of a choanoflagellate, courtesy of ChoanoWiki:
The reason that choanoflagellates have received a lot of attention recently is that they don’t always stay as single cells. Sometimes, as a choaflagellate divides, the cells stay connected to each other. The creatures will form a variety of shapes, including long chains and rosettes:
Image taken from ChoanoWiki.
The fact that these creatures are (1) closely related to the animals, (2) can live as single cells or in mutlicellular groups, and (3) look suspiciously similar to the cells which line the inside of sponges, means that they might provide real insight into the origins of animals. To find out more about what choanoflagellates can teach us regarding animal evolution, I recommend you look at the papers cited in ChoanoWiki. But for now, I’ll leave you with a very cool picture made by fellow classmate Valerie Virta using antibody staining techniques Nicole taught us. This is a colony of choanoflagellates, the blue is staining the bodies of the choanoflagellate bodies, the red is staining the microvillar collar, and the green is staining flagellum (for you technical folks, that’s DAPI, actin, and tubulin):
You can also see a cool (if not particularly informative) I took of a sponge below. Most of the color is generated from natural florescence coming from the skeleton of the sponge (called spicules). But you can see the little blue dots, which are the nuclei of cells stained with DAPI.
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