Keira - A whole lot of larvae (Week 1)

My name is Keira Roberts. I have been a student at Portland Community College for the last 2 years and will be starting at Lewis and Clark College in the fall. I am planning to pursue a course of study in chemistry and, eventually, a career in research. I applied for PRIME in order to learn more about the research options in the marine sciences. I’ve really enjoyed the research experience I’ve had in the past and have been looking forward to learning more about how research is perfumed in different fields. I am also excited about being able to do some fieldwork as a part of scientific research. This summer, I’ll be working with George von Dassow through the COSEE-PRIME internship program. In just the first week, I’ve learned how to perform a variety of tasks and use new equipment (like the camera- microscope that I used to take the pictures). Also, I already been out on a boat to dredge for sand dollars and gone to mudflats to gather Nemertean worms.

This week, I learned how to harvest sperm and eggs from Strongylocentrotus purpuratus (purple sea urchin), Micura alaskensis (local ribbon worm), Patiria miniata (local sea star), and Dendraster excentricus (sand dollar). I have fertilized and raised the larva of each species mentioned here. These freshly fertilized zygotes grow from one cell into two, then four, then a blastula (hollow ball of cells), then further stages of larval development. After a few hours, the larvae have grown cilia and digestive systems. It is truly amazing to watch their rapid development and see firsthand the characteristics unique to each.

This photograph shows two Dendraster excentricus zygotes within a few minutes of fertilization. The darkish circle in the center is the oocyte, or egg. The clear circle surrounding it is the fertilization envelope, which prevents more than one sperm from fertilizing the oocyte. The pink dots surrounding each oocyte are pigment cells embedded in the oocyte’s jelly-like coating. 

My project for this summer will be to study the ability of Dendraster excentricus larva to repair wounds.  I’ll use a laser to shoot off one of their “arms,” pictured below. Then, I’ll study the rate at which the larvae are able to heal their limbs. The ability of larvae to self-repair is remarkable; they are able to repair major damages quickly and develop normally afterward. This study has the potential to further our understanding of wound healing in other eukaryotes; the process of cellular repair is remarkably similar in a variety of organisms. These larvae are useful to study because we can fertilize a great number of them with relative ease and because they heal and grow in a very short period of time. 

This photograph shows a Dendraster excentricus larva about 5 days after fertilization.