Week four has come to an end! This puts us at nearly halfway through our summer internship; research is fully underway by this point. All of my crabs have now molted, which means that I can begin tracking the molt intervals for each treatment. Like many other crustaceans, Dungeness crabs experience growth in a sort of step-wise pattern, rather than linearly. This is due to the presence of their shells, which are calcified tissues; between molts, these animals build mass within their shells, becoming more "packed" inside because their exoskeleton is mostly inflexible. When they are ready to molt, they expand their bodies, opening their old carapace and sliding out of it like a pair of coveralls. When they emerge, they are larger than their previous exoskeleton (some of my crabs increased more than 40% in width!), but are also soft and vulnerable until their new shells harden. However, molting frequently is still advantageous for juveniles, as size can be an important factor in determining whether an individual will be preyed upon by members of its own cohort (age group). Bigger individuals in later instar stages (stages between molts) are more likely to prey on smaller individuals from previous instar stages, even among the same cohort. Because crabs settle in such high densities, avoiding larger members of ones cohort can be difficult, so the ability to forage for food opportunistically to promote growth may be advantageous for juvenile crabs, which is why the question that I'm asking (whether different diets influence growth and molt rates) is so interesting to me. However, collecting data on growth (because crabs do not grow linearly) depends on whether they molt again in the next five weeks. As a contingency plan, there are other related questions that can be investigated, such as: will these crabs, which are generally aggressive, still attack and cannibalize each other if there is an ample supply of food that isn't what they are normally accustomed to consuming, such as algae or urchin pellets? This could explain some preference behaviors of crabs of this age. Or: how does organic composition- protein, fat, and carbohydrate concentration- differ between the crabs from each dietary treatment? This could be used in the future as an index for identifying components of the diets of other crabs.
Our seminar this week focused on the phylogeny of a few types of algae- meaning their relative position on the “Tree of Life.” The speaker, Rick Zeckman, is a professor at Humboldt University, and has been studying various types of algae for a majority of his career. This talk focused on several deep-sea algae (>60ft depths) and their position on the Tree, including giving them a potential new order of their own, called Palmophyllales.
We drove to Eugene on Friday and visited the Museum of Natural and Cultural History and biology department laboratories on the University of Oregon campus. We toured the labs in the Institute of Ecology and Evolution, and learned about some of the interesting research that goes on there. The museum contained a variety of fossils from Oregon's history, including an ancient Ammonite shell, a casting of a giant sloth skeleton (shown above), and a jawbone of a mastodon found in Salem (my hometown!) that dates back to the end of the last Ice Age. Speaking of which, it was also nice to get back into the Willamette valley where it was a little sunnier and warmer than out here at the coast.
As always, thanks for reading!
Hey, readers! My name is Zade Clark-Henry. I'm from Salem, Oregon, and I'm an undergraduate student majoring in Natural Resources at Oregon State University, with an emphasis ecological studies, specifically forest ecosystems and ecological restoration. I'm interested in all types of science, but especially life sciences, and within that I'm most interested in ecological interactions between organisms. My non-academic interests include playing music, hiking, camping, exploring, kayaking, reading, and drinking tasty espresso.