Time for some very delayed news!
Having finally navigated the terrors of ill health, practical issues, and bureaucracy, the research is well underway! Sorry for the lack of updates, but as things progress I will greatly increase my efforts to keep you informed. Also, keep an eye on your inbox's this weekend as I will be sending (much belated) digital gifts to all my backers.
In my previous work, I found that the non-native purple varnish clam, Nuttallia obscurata, will increase its burrowing depth when exposed to a collection of risk cues (chemical signals from crushed varnish clams and physical and chemical signals from crab predators found in the Pacific Northwest). My current project is trying to determine which of the risk cues caused the clams to burrow deeper. To do this my hardworking undergraduate helpers Jessica and Melinda and I first have to tether varnish clams to 20 cm lengths of fishing line. This allows us to determine their burrowing depth without digging them up. And it looks like we are setting up for a tiny, bizarre game of croquet.
Then we place the clams into four sand filled tanks with chilled and aerated saltwater and give them 24 hours to acclimatize. We then added one of four cue treatments to a tank:
- A control with no risk cues
- Crushed varnish clams in a suspended cage, exposing the tethered clams to the smell only.
- A Dungeness crab in a suspended cage, exposing the tethered clams to the smell only.
- A Dungeness crab roaming freely in the tank.
After 72 hours, we take the cues away and measure how deep the clams have burrowed. So far, we have completed 7 of the planned 10 replicates of the experiment. Although we are delaying an in depth statistical analysis of the data until we are finished, I do have the following preliminary data I would like to share with you.
This graph shows the average burrowing depth (cm +/1 SE) of varnish clams exposed to the four treatments. While there is a lot of variability, there are some trends emerging. Varnish clams in tanks with a Dungeness crab burrow, on average, ~3.5 cm deeper than those in the control tanks. Clams in tanks that can smell crushed clams and Dungeness crabs also burrow deeper than control, but nut as much as those in tanks with free crabs. These differences have become become more pronounced as the experiment has proceeded and I am confident that we will wind a statistically significant difference across treatment when we are done.
In a few weeks, I will be done with this current experiment and will set up for the next project: comparing the response of varnish clams from Oregon to those from Japan (in their native range) and British Columbia. I have run into a number of problems collecting these foreign specimens, including the widespread restrictions of clam fisheries in BC due to Paralytic Shellfish Poisoning concerns. However, I am pursuing a number of solutions to these problems and am confident that in the next month or this experiment can proceed.
Where did my money go?
To end this post, I wanted to let my backers know what their generous donations have gone towards so far. I have made a couple trips to the coast, collecting hundreds of clams and dozens of crabs. So far, all of the collected crabs have been successfully returned to their collection site after being used in the experiments (Zero Crab Mortality!). Additionally, their gifts have feed the crabs, clams, and undergrads their favorite treats. The vast majority of the donations are being reserved to cover costs related to the clam collection and importation and will soon be put to good use.
I hope you all enjoyed this update. Thanks again for your support and interest. If anyone has any questions about the project or the topic please feel free to contact me.
Brian "That Clam Guy" Turner