Wednesday, August 1, 2012

Cooking snails (or "experiments with isotopes!")

With Benja on vacation this week, the Big Project for Team Madison has been an ongoing experiment with snails, the goal of which is study maternal investment in Lavegeria nassa communities and measure the production rate of babies using an isotopic labeling method.


Well these snails actively nourish their babies, in that they brood their young inside the shell until they are a safe size to be released (just over 1mm…which is still pretty tiny if you ask me) and then give birth to live young! It’s like a mini conveyor belt of snail production, and we basically want to see whether maternal investment in producing young reflects the quality of the mother’s diet.

Cool stuff, really.

So we picked 3 of our sites that vary in productivity, collected a bunch of cobbles and snails from each, and brought them back to the lab to get cooked (“isotopically labeled”) with 15N. 

And the lucky sites are...2, 4, and 5! 
 [Brief aside: By “the lab” I mean Pete’s former bedroom. 

Complete with drying oven, freezer, and bed!
Normally our Kigoma work is based out of the Tanzanian Fisheries Research Institute (TAFIRI), but this year we arrived to find our lab space in the middle of a complete overhaul (read: total shitshow). So we rolled with the punches and set up base camp at our motel, Aqualodge. I call it the malaria lab, since it doesn’t have a fan and harbors brazillions of (likely-malaria-carrying) mosquitos. Plus it’s super-hot, headlamps are needed even during daylight hours, and it's been known to flood on occasion. It’s definitely sub-optimal…but it has a bed!]

So anyway, the snails…

This isotopes is distinct from what occurs naturally in the lake, so the label allows us to measure the rate at which new babies are produced and current embryos grow. Our study sites differ in productivity, so applying this method in parallel at 3 sites allows us to test the influence of diet and whether populations of the same species may have evolved different maternal investment strategies.

Since the goal was to put them back out in the wild and collect them at various time intervals, we had to make them stand out in some way from all the other snails at each site. So after Renalda bought the brightest nail polish she could find in Kigoma, Vanessa was tasked with making them pretty.

I like to think the other, non-polished snails were jealous. In a show of solidarity, I painted my toenails purple (which, for those of you who know me personally is not at ALL in line with my personality...)
After letting them “cook” for a few days, Ben and I took them back to the sites where they originated, found big, flat rocks surrounded by sand so they’d have a lower chance of…wandering off, and let them go.

The release was about as dramatic as you'd imagine, but they didn't stay on those rocks for long...
I know what you’re probably thinking: THEY’RE SNAILS. How far could they possibly go?

That’s what I thought too, but we apparently have some ambitious snails in the group. Prevailing theory said they’d only move a meter or so per day, but collecting them has become... challenging...after only a week. For example, a few abandoned the conditions at 3.5 meters and climbed the Mt. Everest of site 4 (I would have loved to watch time-lapse footage of that feat!). 

The plan is to collect them every week or so until we leave for the summer, and after every collection I try to consolidate them all on a rock. At some point it will involve SCUBA diving, but for now I can still find them by snorkeling.  
Three collections are done, and 7 more await. Here's hoping they don’t wander too far…


  1. ok, but WHERE is the photo of your purple pedicure?

  2. i had a feeling the masses would need proof ;). i'll do a touchup and post a pic later. i might try the blue this time though...!