Flow through a bare sponge skeleton is not informative about how flow moves through live sponges

Friday 22 Apr 22
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Seyed Saeed Asadzadeh
Postdoc
DTU Aqua

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Thomas Kiørboe
Professor
DTU Aqua
+45 35 88 34 01

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Poul Scheel Larsen
Professor Emeritus
DTU Mechanical Engineering
+45 45 25 41 70

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Jens Honore Walther
Professor
DTU Mechanical Engineering
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The deep-sea glass sponge Euplectella aspergillum is well known due to its beautiful lattice-work structure, and has attracted interest in its solid and fluid mechanical properties. In a recent paper, we argue that including sponge tissue is key in understanding the hydrodynamics of these beautiful animals, and an analysis of their hydrodynamics where the true dimensions and flow resistance of the sponge aquiferous system are omitted is not informative about the flow patterns inside the sponge and thus about the sponge biology.

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

https://www.oceanlifecentre.dk/news/nyhed?id=693836e9-3a70-4905-9db7-c8471b674d9e
17 MAY 2022