Swimming mechanisms in marine larvae - how to become fast when you are small.

Marine planktonic animals live in a world that is radically different from ours. The physical properties affecting the movement in these small sized aquatic animals highly differ from those faced by animals of larger size. When small sized animals swim, they do so at a biologically low Reynold’s number (the ratio of inertial forces to viscous forces within a fluid). At low Reynold’s numbers, viscous forces dominate, inducing a boundary layer around the body that the animal has to overcome to move. In this way, seawater is viscous for small planktonic animals, and swimming through water becomes the equivalent of a human swimming in sticky syrup. We addressed the physical-biological framework involved in swimming of planktonic organisms, using barnacle larvae as model group. Barnacles are highly important organisms in marine intertidal ecosystems. Their planktonic larvae are extremely fast, yet how they are able to reach high speeds has been unknown. Swimming mechanics in planktonic organisms are poorly understood, due to complex fluid physics. However, recent advances in microscope technology have made it possible for us to unravel the secrets of microscopic swimmers. In a comparative approach between larvae of different species, swimming methods, kinematics, fluid flow around the larvae, and their adaptions to the physical properties of seawater were investigated. Larval swimming behaviour and mechanisms has been investigated in controlled laboratory experiments using state of the art high-speed video microscopy and micron resolution particle image velocimetry (micro-PIV), a technique that rapidly evolved in recent years. Scanning Electron Microscopy is utilized to study the morphological fine structures used for active propulsion and passive structures that optimize hydrodynamics.

Prosjektet har fremmet internasjonal mobilitet og karriereutvikling for en forsker som er tidlig i karrieren. Prosjektet bidro videre til tverrfaglig samarbeid og etablert en tettere samarbeid mellom forsker ved Universitetet i Bergen og Danmarks Tekniske Universitet. Prosjektet har øke vært forståelse av det fysisk-biologiske rammeverket som er involvert i bevegelsen av marine planktonorganismer og deres tilpasninger til de fysiske egenskapene til sjøvann.

The proposed project will investigate the mechanisms behind the locomotion in marine planktonic larvae and their adaptions to the physical properties of seawater, where small sized animals have to overcome the constrains of living in a low Reynold's number system. In the initial two years of the project, the young researcher will be integrated in the working group of Professor Thomas Kiørboe at the Technical University of Denmark, and in the final year he will return to his home institution in Norway, the University of Bergen. In the proposed project the mechanisms behind the locomotion in small marine organisms will be investigated using barnacle larvae as model organisms. Barnacles are popular models for the study of larval development and are excellent organisms for experiments due to their abundance and ability to be reared under laboratory conditions. In a comparative approach between different species, larvae will be investigated for swimming methods, kinematics, and fluid flow around the larvae, and their adaptions to the physical properties of seawater. Larval swimming behaviour and mechanisms will be investigated in controlled laboratory experiments using state of the art high-speed video microscopy and micron resolution particle image velocimetry (micro-PIV), a technique that rapidly evolved in recent years. Scanning Electron Microscopy will be utilized to study the morphological fine structures used for active propulsion and passive structures that optimize hydrodynamics.