After a nice orientation to the island and introduction to the course yesterday, we jumped into histology/histopathology head-first. Luckily, we weren’t thrown into the deep end without at least some floaties.
Today’s lectures included an overview of molluscan (abalone and bivalve) anatomy and diseases as seen in histo. It seemed much more straightforward on the powerpoint slides than in practice, but we’ll get to that in a bit.
Before we looked at the histo slides, we familiarized ourselves with the fresh specimens through vivisections (I did not know this word was so charged). While it may seem cruel to cut the inverts while they’re still alive, it is very helpful for us to see the function and location of body parts to translate them to our understanding of histo slides. The inverts were anesthetized before we did anything with them.
We first opened up some mussels: Mytilus edulis and Mytilus californianus, assuming my IDs are accurate. We first cut the hinge ligament and then sliced the posterior and anterior adductor muscles holding the valves together. After this, we scraped off the mantle on one valve so that the whole body lay on one side.
The first image is M. californianus with the left (?) mantle removed. The deep orange-y stuff on the top is gonad, which we at first thought was ovary, but a quick google search and a look under the microscope (below) revealed that our believed-to-be girl mussel was actually a boy. We were able to figure out much of the mussel’s anatomy, but its heart escaped us.
Next we dissected a Pisaster ochraceus, which was lovely and purple, albeit showing signs of wasting disease (twisting and lesions). It was also incredibly ossified, which made chopping into it very difficult. Fortunately we had the great Morgan to help us get to the goodies inside.
The inside of the sea star was pretty neat. We were able to see gonads (ours presumably male), ampulla for each of the tube feet, and digestive caeca. It was cool to see how the ampullae controlled individual tube feet by squeezing them.
In the afternoon, we began our ventures into the histo slides. I had hoped that I would be an expert after the lectures, but the slides proved to be worthy adversaries. I was often left stumped, trying to figure out which tiny pink spots were which. It was very satisfying to have been able to find rickettsia (dark spots/colonies in the posterior esophagus of an abalone), Bonamia (little dots in enlarged hemocytes with offset nuclei), and ferritin granules. It’s clear that I need more experience looking at slides, but it’s very exciting to learn more about a tool that I’ve seen used so often.