In a recent publication, Falcucci et al. set out to study the hydrodynamic implications of the architecture of the skeleton of the deep-sea glass sponge Euplectella aspergillum using "extreme flow simulations". Using a model of the bare skeleton of the sponge, the authors investigate the flow patterns inside and downstream of the passive sponge skeleton exposed to external flows, and suggest that the skeletal motifs give rise to internal recirculation patterns favoring the sponge feeding and sexual production. Unfortunately, in their model Falcucci et al. disregard the sponge "tissue" covering the body wall and the aquiferous systems which, we argue, are key to the formation of any internal or external flow patterns because of a much lower porosity and thus higher flow resistance than that of the bare skeleton which is, in fact, not in direct contact with the water flow.
Picture: drawings of the soft tissues of the glass sponge Euplectella aspergillum Owen.
Read the paper here: https://www.nature.com/articles/s41586-021-04380-8 arising from G. Falcucci et al. Nature https://www.nature.com/articles/s41586-021-03658-1 and replying to SP Leys Nature https://www.nature.com/articles/s41586-021-04381-7