Laura A. Miller is in the Departments of Mathematics and Biomedical Engineering, University of Arizona, Tucson, Arizona 85721, USA.
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The deep-sea sponge Euplectella aspergillum, also known as Venus’s flower basket, is celebrated for its intricate glass skeleton. This structure provides remarkable mechanical support and has inspired a generation of strong, lightweight bridges and skyscrapers1. Water is continuously drawn into and out of the sponge’s central body cavity through pores, to filter food particles and exchange gases. Although the mechanical properties of the sponge’s skeleton are well documented, little is known about the detailed fluid flows around and through the organism. In a paper in Nature, Falcucci et al.2 use state-of-the-art fluid-dynamics simulations to resolve these flows. Their results show that the sponge’s structural elements reduce the impact of hydrodynamic forces on the organism and generate internal circulation patterns that might be used for feeding and sexual reproduction.
The skeleton of E. aspergillum consists of a regular square lattice that is diagonally reinforced and forms scaffolding for the sponge’s hollow cylindrical body3 (Fig. 1). In addition, external ridges spiral around the main body and are superimposed on the lattice. To deconstruct the effect of each skeletal component on the fluid flows, Falcucci and colleagues generated several idealized models of the sponge for comparison. These models included a plain solid cylinder, a solid cylinder with helical ridges, a hollow cylindrical lattice and a hollow cylindrical lattice with helical ridges.