DISSERTATION RESEARCH: The Effect of Hydrodynamics on the Evolution of Bryozoan Colony Form

Duke University, Durham NC

Investigators

Abstract

Dr. Steven Vogel & Marney C. Pratt Colonies of bryozoans, widespread and abundant filter-feeding animals, encompass a great variety of shapes and sizes. But, since colonies of most bryozoans can grow in any direction, still more diverse colony shapes should be possible. That only a relatively small subset of the theoretically possible shapes occur suggests that certain shapes have significant advantages over others. Since bryozoans are filter feeders, hydrodynamic factors (particularly water velocity) could determine bryozoan colony form by affecting their ability to capture food. This study addresses the role of hydrodynamics by assessing how water velocity affects particle capture in the major colonial growth forms. It has four principal elements: (1) measurement of particle capture success for bryozoans with different colony growth forms over a range of flow velocities, (2) measurement of the effect of feeding structure location on feeding success, and the assessment of how that might influence colony shape, (3) the use of flow visualization to determine the effect of colony form on the water flow around and through colonies, and (4) measurement in the field of the abundance, growth, and survival of bryozoans living at different water velocities. By delineating the web of relationships linking colony form, habitat hydrodynamics, and feeding success, this study should contribute to our understanding of how an abiotic factor such as hydrodynamics can influence the evolution of colony form. Its findings should be applicable to many other kinds of colonial filter feeders, systems whose greater aggregate taxonomic differences cloud comparisons of analogous morphological diversity.