Hydrodynamic effects of mastigonemes in Cryptophytes *

Cryptophytes are aquatic unicellular eukaryotes that inhabit both marine and freshwater environments worldwide and whose photosynthetic forms may be responsible for a large part of primary carbon production. Cryptophytes have flattened, elliptical cells and swim using two flagella that are known to bear rigid mastigonemes, fibrous ultrastructures of a nanometer-scale thickness. It has been claimed that by affecting the drag of flagella, mastigonemes can affect swimming behavior — even reversing swimming direction, but the hydrodynamic effect of these filaments seems to be different for different species. In this study, we experimentally investigate flagellar kinematics and mastigoneme geometry on Chilomonas paramecium through high-speed imaging of freely swimming cells, and SEM and TEM imaging. We then numerically investigate the hydrodynamic effects of these mastigonemes using the method of regularized Stokeslets. Finally, we also study and simulate the kinematics of a singly flagellated protist, which we believe may be a haploid form of Chilomonas paramecium.