This week involved trying to tie up a few loose ends to complete my project. One of these loose ends was an experiment to account for the effect of gravity on the swimming speed of Pleurobrachia. My intention was to get a general idea of how fast Pleruobrachia sink or float when they are anaesthetized. Knowing the average speed of sinking/floating would allow me to account for the combined effect of gravity, buoyancy and drag on the swimming speed measurements I made a couple weeks ago. However, this proved to be very difficult. My initial idea was to use magnesium chloride, which is a common anesthetic, and then take videos of the organisms sinking or floating. It turns out that magnesium chloride does not stop the comb plates from moving. This is because the comb plates are coordinated mechanically, not by the nervous system. Thus, the comb plates can still move even when magnesium chloride has inhibited nervous conduction. This caused a lot of problems for me. After exposing the organisms to magnesium chloride in a small dish, I noticed that there was some decrease in activity but metachronal waves still traveled down the comb rows as expected. This activity in the comb rows allowed the organisms to move around, especially when transferred to a larger tank where the concentration of magnesium was low compared to the volume. There were only a couple times that I observed sinking or floating with low comb row activity, but these periods were short and few and far between. The organisms also regained normal activity very quickly after being transferred to the tank so any measurements I was going to make had to be very fast. These problems culminated in me being unable to make measurements of the speed of sinking or floating using my original methods.
This was frustrating as my project was very close to complete but it seemed like I was hitting a lot of road blocks right before the finish line. My last idea was to excise the statocyst, which is a sensory organ that ultimately controls the transmission of metachronal waves down the comb rows. I planned to do this using a micropipette, which allows me to use light suction to remove the statocyst. However, I don’t have that many organisms in the lab right now, so I don’t have much margin for error. I decided to hold off on this aspect of my project until next week for a couple reasons. For one, we have a draft of our final poster due early next week so I ended up spending the last part of my week making figures and putting together my poster. In addition, we were required to do public outreach at the Charleston Marine Life Center on Thursday of this week and I wanted to have live animals in my exhibit. Hopefully, my gravity experiments will go better next week. It’s not critical that I include this part of my project, but it would be a nice compliment to the work that I have already done.
My name is Wyatt Heimbichner Goebel and I am a marine biology major at Western Washington University. I love biology, specifically marine mammal ecology and biomechanics. I’m always up for conversations about music, poetry, and weird biology facts.