Choanoflagellates are filter feeders and an important component of microbial foodwebs. Because they are the ancestors of multicellular life, they have been intensely studied. Some species build an elaborate external ribbon structure. Its function is unknown but we demonstrate that it may significantly increase prey capture efficiency.
Some choanoflagellates (over 150 species) construct a very ornate extra-cellular basket-like structure, known as the lorica. The presence of the lorica is puzzling; what could be the benefit of having such rather large structure around the cell? Using computational fluid dynamics (CFD), we study the flow around a single but representative model organism (Diaphanoeca. grandis) with and without its lorica to elucidate the hydrodynamic functions of the lorica and to test the validity of the several previously proposed functionalities, namely increasing the feeding rate and reducing the swimming speed. Our results provide no support for these hypotheses. Rather, our simulations suggest that the main function of the lorica is to enhance the prey capture efficiency, but this happens at the cost of lower encounter rate with motile prey.
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Asadzadeh SS, Nielsen LT, Andersen A, Dölger J, Kiørboe T, Larsen PS, Walther JH (2019) Hydrodynamic functionality of the lorica in choanoflagellates. J Roy Soc Interface 16: 20180478. https://doi.org/10.1098/rsif.2018.0478