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Embryology

A (sea) star is born: reproduction and early development in marine invertebrates
Dates: April 13- May 1, 2026
Instructor: Zak Swartz, Ph.D. (zswartz@mbl.edu) (MBL)
Teaching Assistants: Jamie MacKinnon, Beverly Naigles,Brian McGonagle
Location: Loeb Laboratory, MBL, Woods Hole, MA

Course description

How do animals make eggs, and how do eggs make animals? How does the environment affect these processes? The most diverse group of animals in our oceans is the invertebrates. In this course, students will learn broad concepts in animal reproduction and development, from a biomedical, evolutionary, and climate perspective. Topics will include oogenesis, meiosis, fertilization, early development, and germ line specification, covered through morning lectures and journal club discussions of research papers. We will approach these topics through a cell biological and gene regulatory lens. In the lab, we will primarily work with the bat star Patiria miniata, but also with sea urchin species that we will collect locally from Vineyard Sound (weather and spawning season permitting). Students will learn essential cell biological and embryological techniques including gamete and embryo/larval culture, staining, microinjection, and live imaging. Students will conduct independent embryology projects focusing on marine invertebrate reproduction and embryogenesis.   

Course structure

  • Lectures (10:00-12:00am) 3 mornings per week during the first two weeks of the course. These will provide an overview of the field and involve active discussion.
  1. Marine invertebrate diversity and lifecycle
  2. Oogenesis (egg development) and Meiosis
  3. Fertilization
  4. Early development
  5. Gastrulation and larval development
  6. Germ line specification
  7. Environmental impacts on development and reproduction
  • Journal Club: 3 total, group discussion of a paper in reproduction or developmental biology relevant for the course topics. Students will read papers for understanding and come prepared with written questions for discussion. We will discuss the primary findings, caveats, and ideas for future directions. 
  • Labs (1:30-5:00pm): Week 1 – lab introduction, safety, animal handling, gamete collection, fertilization, embryo culture, microscopy, microinjection. The remainder of weeks 2 and 3 you will carry out team projects (selected from suggested ideas or developed independently) to either 1) test the impact of environmental perturbations on fertilization and embryonic development or 2) use new CRISPR-Cas9 tools to test the function of conserved developmental genes in sea star embryo development. These independent experiments will be summarized and presented to the class at the end of the final week. Students must work in groups of 2 or 3.
  • Animal collection trip (weather-dependent): We will participate in a collecting trip on R/V Gemma in which we will dredge for local species including sea urchins and sea stars. We will use these specimens to undertake comparative experiments in the lab.

Course objectives

In this course you will build your knowledge of a wide range of topics related to reproduction and embryonic development. Following this course, you will be able to:

  1. Explain the fundamentals of oogenesis, fertilization, early development, and germ line specification.
  2. Use fluorescent light microscopy to visualize and interpret cellular events in development.
  3. Critically read and discuss scientific literature related to reproductive and developmental biology.
  4. Develop a plan for a feasible, well-controlled independent experiment which will be then conducted in small groups (depending on class size) using echinoderm research organisms, including sea stars and sea urchins.
  5. Craft and present an oral scientific presentation that provides background, results, and conclusions, while incorporating peer feedback from a practice run.

Assessments

Course objectives 1 and 2 will be evaluated by short quizzes at the end of weeks 1 and 2 (15 % each, 30% total). Objective 3 will be evaluated by short written (1 paragraph) summaries that include a question for the group in advance of our discussion (8.3% each, 25% total). Objective 4 will be evaluated by submitting a 1-page plan for the independent experiment (completed in small groups), including background and significance, hypothesis to be tested, experimental plan, and how results will be interpreted (25%). Objective 5 will be assessed through a 5–10-minute presentation (20%).