CAREER: Consequences of Short-Term Food Variability During the Development of Marine Invertebrate Larvae

San Diego State University Foundation, San Diego CA

Investigators

Abstract

Most bottom-dwelling invertebrate animals have complex life cycles that include pelagic larvae. Many of these larvae feed in the plankton as they develop, grow, and disperse to habitats where they settle and metamorphose to benthic juveniles. The duration of the larval period is central to any model of transport and recruitment. Similarly, the size at metamorphosis can contribute to the success of newly settled recruits. The rates of larval development and growth have long been known to be influenced by larval nutrition, and recent data on small-scale patchiness in the plankton underscore the prevalence of short-term food variability in nature. Previous efforts to quantify the effects of food variability as larvae develop in the plankton have, however, been limited. In contrast, ecologists studying the life cycles of amphibians and insects have created several theoretical models and performed comprehensive experiments to test the effects of environmental variability on the timing of and size at metamorphosis. This study will apply lessons learned from ecological studies of amphibian and insect metamorphosis to test the effects of short-term food variability during the development of marine invertebrates. Lab experiments will be performed on diverse larvae (polychaetes, bivalves, crustaceans, echinoderms) to test the quantitative predictions of a theoretical model of larval development and growth in the context of short-term food variability. The theoretical framework and empirical data will foster a comprehensive understanding of the effects of food variability, which then can be incorporated into oceanographic models of dispersal and recruitment. In addition to measuring the timing of and size at metamorphosis in variable feeding regimes, the temporal expression of microRNAs that are known to regulate the timing of development also will be measured, with the aim of acquiring new tools to assay larvae in situ. Education and outreach will be integrated explicitly into the research program by having teams of undergraduate students perform many of the experiments as part of a year-long capstone course ("Senior Research Experience: Marine Invertebrate Larvae") and by developing a peer-mentoring program involving high-school teachers and their students (LEARN: Larval Ecology And Research Networking). In the first semester of the capstone course, undergraduates will learn the diversity of invertebrate larval forms, practice techniques for culturing larvae, and develop individual research proposals focused on a species of interest. Students will review proposals written by their peers and evaluate the proposals in a panel-review setting. In the second semester, teams of four students will collaborate to revise the proposals into group projects and then perform the experiments. Most larval-feeding experiments are not technically difficult, but they are very labor intensive. Working and learning in cooperative teams will distribute the workload and enrich the educational experience. Undergraduate teams will compile video journals during their research and will present their projects in four formats: a scientific paper, an oral presentation, a poster, and a presentation to a high-school biology class as part of the LEARN program. LEARN will be a program involving the PI and his undergraduate students collaborating with high-school biology teachers and their students. The program will target inner-city and ethnically diverse high schools. The program's centerpiece will encompass high-school biology classes performing larval feeding experiments on hardy crustaceans that have larval periods lasting just a few days. These simple experiments will parallel the more elaborate ones performed by the senior undergraduates, creating a common theme to facilitate discussion and peer mentoring between the high-school and college students. The program's design will be refined each year during workshops involving the PI and the high-school teachers, and additional workshops will aid the undergraduates in mentoring the high-school students. Furthermore, the LEARN program will include opportunities for the high-school teachers and students to participate as summer interns in the PI's research lab.