Thursday, April 20, 2017

One of these things is a lot like the others

"Hey Lauren, can I show you something?" I called to my advisor. I was seated at the lab bench, in front of the nice dissecting microscope.

"Sure," she strode over, and we switched places. She sat at the scope while I stood beside. Peering into the eyepieces, she could see one of my fouling panels. More specifically, she could see small organisms on my panel.

The organisms were tiny - hard to see even with magnification - and green. Their hard shells were vase-shaped and translucent. I knew I had seen them before, on fouling panels I had deployed in the Arctic in 2014-2015, but I couldn't remember what the organisms were.

Four individuals of Folliculina, photographed under a
dissecting microscope at 50x magnification
"Maybe they're foraminiferans," I suggested to Lauren. I vaguely remembered the organisms being non-animals. They were single-celled, like foraminiferans, I thought.

Lauren has much more experience looking at foraminiferans on fouling panels than me, and she actually disagreed. She continued to peer into the microscope, adjust the focus, move the plate around. "Could they be ciliates?" she asked.

Ciliates!

Suddenly, my memories became crystal clear. A dear Russian colleague had identified the organisms for me in Svalbard. They were ciliates, a kind of single-celled organism that feeds on tiny bacteria and algae in the water. I remembered their name started with an F, and a quick online search helped me find it: Folliculina.

Because Folliculina is not an animal (animals are multi-cellular; ciliates like Folliculina are single-celled organisms), it is technically outside the scope of my succession study (my original plan was to study the benthic invertebrate animals). Lauren and I talked briefly about whether I should count the organisms on my panels, and we decided yes, I should. The more I learn about Folliculina, the more I believe we made the right decision. Get this:

Folliculina are actually unusual among the ciliates because they're sessile. They attach themselves to a surface, build a hard test, and stay in one place for most of their lives - just like the benthic invertebrate animals I'm interested in! They also feed by gathering small particles from the water around them - very similar to benthic invertebrates! As single-celled organisms, they reproduce by fission (one cell divides into two), but after division, one of the new cells will leave the test. It will swim freely in the water for a short period of time and eventually find a new place to settle. This type of life cycle - swimming babies that grow up to be sessile adults - is exactly the type of life cycle that benthic invertebrates follow. I even found a scientific paper that refers to young Folliculina as "larvae!"

Clearly, there are some strong similarities between single-celled Folliculina and the benthic invertebrate animals that are the target of my study. It amazes me that organisms that are seemingly so different - single- versus multi-celled! - can have such similar lifestyles.

I'm glad to include Folliculina in my succession study. Isn't ecology fascinating?

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