In the Sebens Lab in Seattle, we are very lucky to have a group of fantastic interns. This fall, we’ve been spending a lot of time sorting through sediment samples from an experiment we conducted in West Seattle last summer. After many, many hours in the lab, the Sebens Lab interns are true experts at finding and extracting worms, clams, and other critters in sediment samples. Inevitably when you’re doing this type of work, you come to favor certain organisms, be it for their beauty, their bizarre life history, their unusual appearance, or the ease with which you can find them within an expanse of similarly sized sand grains. For this post, two interns, Monisha Ray and Amy Green, have provided us with a look into their favorite soft sediment organisms and a description of what they like about them.
One of the most interesting finds for me while processing our enrichment sediment samples was the presence of ostracods, tiny crustaceans that look like little reddish brown sesame seeds. Although they are related to shrimp, they have a clam-like resemblance due to the valves that enclose the rest of their body. These valves are made up of calcite or chitin. Usually the body of the ostracod ranges from 0.2 to 1mm, but the ostracods in our sediment analysis tended to be a bit larger (2-4mm) which was interesting to note. They were almost easy to overlook as some sort of marine seed, until upon closer examination the bivalved hinge becomes apparent as well as the sensory and swimming appendages protruding from within the carapace. Up to a third of the body of ostracods is dedicated to their reproductive organs, and the sperm of an ostracod can be up to 10 times the length of the body. Certain species of ostracods are also bioluminescent and produce a blue light that has been observed in Japan and Australia amongst other regions. Although the ones in our sample weren’t quite this spectacular, they were still an interesting find and a new encounter for me in my marine science experience.
My favorite infauna genus includes the Lacuna marine gastropod. In the family Littorinidae, they are commonly known as chink shells. They are found on eelgrass, rocks and seaweed low in the intertidal. They are herbivores and lay egg clusters that look like tiny donuts colored yellow or tan (kind of like spaghetti-Os). They have a thin shell with five to six whorls. The shell seems smooth to the naked eye, but has fine spiral ridges upon magnification. They usually have brown bands on whorls, but not always. A study done by Chavanich and Harris (2001) in the Gulf of Maine found that L. vincta prefer Antithamnionella floccose, Ulva lactuca and Laminaria saccharina. These charismatic snails are my favorite because of their pretty banding, and cute squat shape.
Check in soon for more postings on soft sediment organisms and our work in the lab. And thanks so much for reading!