We’re Cuckoo for Copepods
The alarm goes off on my phone. I simultaneously acknowledge and try to ignore it. Try. It’s 4 am and too early to be alive, and yet here I am, trying to calculate how many times I can press snooze and still be on time.
Today is sample day.
I eventually dredge myself out of bed and get ready. Now that my brain is booting up, I start to feel excited again. After all, this is the first time I’ve ever done fieldwork for my major, so it doesn’t matter that it’s just a sample collection. My phone buzzes: they’re here. After a final check to be sure I have everything, I hurry outside and get into our sketchy looking lab van.
Location: Point Dume
Date: July 3, 2019
Party: Sam the man, they call me Logan, and Asher pod catcher.
Objective: collect all the samples, disturb some ecosystems, protect UCSB
After a short drive, we finally reach Point Dume state beach, where we unload our weapons of choice: tupperware and turkey basters. We prowl the edges of the rocky beach, flashing our lights into the various tide pools hidden within the craggy boulders. Our target: Tigriopus californicus, sometimes known as the tiger copepod. Although they’re small, tigs have a remarkable tolerance to conditions that would kill many other creatures, such as low pH, high temperatures, and low levels of oxygen. Furthermore, many scientific papers show that these tolerances vary based on the climate and location of where the tigs live. Our research project aims to find what role, if any, genetics plays in these differences. But before we can get to that, we first need to awaken our inner pokemon fan and catch some tigs.
Back at UCSB, we began the process of labeling our samples and testing the range of tolerances of our tigs. For this experiment, we specifically focus on thermal tolerances to explore how different populations will be able to handle increasing ocean temperatures. To do this, we calculate the lethal temperature 50% (LT50) by putting our tigs through an almost-literal trial by fire. The most accurate way to determine a population’s LT50 is by slowly increasing the temperature of the tig’s environment up to a high temperature, then maintaining that temperature for a while. Luckily, a thermal cycler can do just that, and tigs are small enough that we can comfortably fit 5 of them into a PCR well. We do this through the incredible and highly competitive process known as tig loading.
Thermal Tolerance Testing
12 8-well PCR tube strips
480 T. californicus (if doing a complete 96 well plate)
1 Micropipette, set at 24 microliters
1 Thermal cycler
∞ Amounts of patience
preheating programming your cycler with a temperature gradient of 36-38°C.
Contemplate your life choices as you meticulously fish out 480 tigs using the micropipette as an inefficient vacuum.
Catching multiple tigs at once gives you bonus points.
Panic when you realize you lost your place loading the wells.
Place loaded wells into your cycler for 3 hours total: two to slowly bring the temperature up, then one hour at that temperature.
Remove and serve hot.
We then fully accept our fate as hunchbacks and use a dissecting microscope to look for survivors in each well. By counting the number of fatalities, we can calculate the proportion of survival at each individual temperature. This gives us survivor proportion as a dependant variable with respect to temperature, which can be easily plotted onto a graph using RStudio. The best part about using RStudio is that the different thermal tolerance graphs we plot can be combined with each other into a single graph, giving us an easy-to-read visual comparison between populations.
And that’s a wrap! Between the early morning collecting and giving myself nearsighted blindness, I think I’m ready to call it a day. This was definitely one of the more eventful days I’ve had in the lab, but I really enjoyed it. It’s really starting to feel like I’m contributing to the lab and project. Tomorrow will be another busy day setting up cultures for out tigs, and a few days later will be another sampling trip. I can hardly wait!