Sponges are one of the earliest evolved, and simplest, groups of animals. They are multicellular but lack the typical organization of other animals with e.g. anterior-posterior polarity and nerves. Sponges are sessile animals with water-pumping choanocyte chambers. They share a number of characteristics with other filter-feeding animals. However, they also share characteristics with choanoflagellates, a group of filter feeding flagellates believed to be the sister group to all animals including sponges; they are not ancestral as such, but share a common ancestor. In this project we will study the bioenergetics and bio-fluid mechanical properties of free-living choanoflagellates, colonial choanoflagellates and sponges. Our goal is to investigate, elucidate and quantify the major differences in functional biology of unicellular choanoflagellates and multicellular sponges in order to identify the evolutionary steps that enabled the development of multicellular sponges in which the entire body is specialized for filter-feeding, and to therefore understand a critical step in the history of animal evolution. The project is focused on comparative morphology combined with experimentally measured bioenergetic parameters, including filtration, respiration, particle capture efficiency, food ingestion and excretion in sponges and choanoflagellates. Bio-fluid mechanical studies will also play a central role in the project where we will track particle motion and flow fields around free-swimming choanoflagellates, colonies of choanoflagellates, and the internal water flows through sponge canals and filters. We will also explore the mixing created by exhalant jet-currents from the sessile sponge colonies. Observations will lead to detailed biophysical models explaining the flow patterns and dynamics of food capture in all of the studied organisms. Finally, we want to explore the origin and evolution of a multicellular water-pumping sponge from a phylogenetic point of view.
Link to Home page for project.
Grant Provider: Villum Fonden
Total Amount of Grant: 6.398.350 DKR (to SDU: 2.965.200 DKR)
Period: 2/3 2015 – 1/10 2019
Grant No.: 95-306-