Monday, January 23, 2012

Photo Time

Because I haven't posted a photo in way too long and it's winter and even though it hasn't been that bad we still need to be reminded the green is coming back, here's a photo: it's of moss!

Salt Marsh Snails

I've been meaning to write this post for a while but I hand't managed to figure out what the upshot or the moral of this story was. I think I figured it out so here goes:

Back in the fall I led a trip with some Boston Public teachers and their students to a local salt marsh. I visited the classrooms before and after the trip to support the students' learning and the teachers' goals (and their learning as well).

There are two main types of snails you see in Northeast salt marshes, littorina littorea, the common periwinkle and melampus coffeus, the coffee bean snail. Littorina is marine, it breathes water and spends most of its time under water while melampus is terrestrial, it breathes air and while it lives right on the edges of tidal creeks it is never seen in the water. When the tide moves melampus will react by climbing a stalk of marsh grass to avoid being drowned.

During my trip back to the classroom with one of the teachers I found she had a book about salt marshes and I had a little down time before I met the students so I decided to flip through the book. I found a photograph of what looked like littorina climbing up marsh grass with a description that periwinkles climbed up to avoid drowning. "Hrmm..." I thought. I knew that periwinkles were marine and I had never seen this behavior before. Littorina tends to eat algae and not marsh grass so I thought, "maybe it's feeding, but I doubt it." I talked to the teacher who had used that image during one of her lessons. "I'm really not sure what's going on in that image, but I'll look into it."

So I did and I discovered that it was indeed littorina in the photo, just not littorina littorea. It was another salt marsh snail (in fact common name, salt marsh periwinkle), littorina irrorata. These periwinkles do feed preferentially on marsh grass and not algae and I quickly turned up a number of similar images of littorina irrorata climbing up grass to feed. Apparently this species can be found as far north as Massachusetts but is more common slightly further south so I was not as familiar with this snail.

At first I thought this story was about being careful about what you read, especially when it is written by non-scientists (like me!) and to fact check your sources. But that's an old story and most of us have heard dozens like it. I realized that this story really held a moral for me and not the teacher. I didn't realize this because I instinctively acted on the moral, I did the research, figured out what the image was all about and reported back to let her know what I had found. I didn't just throw up my hands and say "Oh, it's probably just l. littorina doing something weird I've never seen before."

So I think the moral is this: it's most important to make sure you know what you're talking about when you are the specialist. As an ambassador for robust inquiry science education it is even more imperative for me to assume I don't know everything and that when I see something that doesn't fit my preconceptions it is even more important for me to do the research so I can reconcile the new information. So I encourage all of you who are science educators in any respect to always be on guard, especially when you think you know exactly what you're talking about. You may be surprised that you don't...and you might actually learn something.

Thursday, January 12, 2012

More on Alive or Not Alive

Speaking of Carl Zimmer and speaking of things that might be alive, celebrated curiosity monger Carl Zimmer posted this on his blog:

I scrolled down to the comments and immediately got a science headache. Not recommended unless you're actually a taxonomist.

Stay tuned, an actual post has been brewing...

Saturday, January 7, 2012

Natural History Reading: Parasite Rex

I just finished reading Parasite Rex by my hero, Carl Zimmer. The last natural history book I read and wrote about here on the network, the Secret Life of Lobsters I found somewhat lackluster and difficult to get through so this read was a breath of fresh air.

As usual, Zimmer tells the story of his interactions with the scientists who study parasites so eloquently and so intimately that it demands your attention and your affection. He makes the often bizarre and macabre-seeming world of tapeworms, hookworms, flukes and ticks exciting and wonderful.

I don't want to spoil too much of the fantastic science in this book but something Zimmer continues to come back to throughout is how much our still-burgeoning understanding of parasitology has begun to really change our understanding of what we thought were hard and fast ecological concepts. One example he gives has to do with the common notion that part of the ecological services that large predators (such as wolves) provide is to reduce the spread of disease through an ecosystem. Prior thinking goes like this: animals that are sick are easier to catch so predators spend less energy if they target these sick animals as food sources instead of healthy animals. This will benefit the ecology because that sick animal is now out of the ecology, it can no longer spread its disease to other members of its species or possibly other species.

The problem is that parasites (and parasites here are defined as all eukaryotes, so animals plants and fungi, that spend all or part of their life cycle either inside a host or feeding directly from a host) often spend part of their lives in one species and another part of their lives inside another species. Let's say there's a species of worm that infects a moose in one part of its live and a wolf in another. Natural selection will have provided that worm with an ability to modify the moose's behavior such that it is easily caught by wolves. It is in that worm's best evolutionary interest to continue its life cycle. So the wolf isn't reducing the spread of disease at all. It's actually actively taking part in spreading the disease. While the previous thinking still can apply to bacterial and viral infections it may have the exact reverse process with eukaryotic parasites.

He also gives descriptions of how many parasites change the behavior of their initial host so drastically that they make food more available for the predators. There is a particular parasite that infects killifish, a small salt marsh fish, and then herons. The behavior of infected killifish is so drastic that it makes them 30% more likely to be caught. This may not be entirely sound but one way to look at this is that food is 30% more available for the herons therefore the marsh can support a larger population of the birds than it could if this particular parasite did not exist. The parasite isn't exactly increasing the amount of food but it is increasing its availability.

This book really made me rethink some of what I know about ecology in some pretty interesting ways. As I mentioned it is written in Zimmer's usual smooth and easy to read prose. His writing is easily accessible and he is one of the best authors for those who are interested in science but feel intimidated or don't think they have a solid background. Parasite Rex was absolutely a great read.