Science Delights: Lessons from Venus's Flower Basket

"One of the most singular and beautiful as well as the rarest of the marine productions.... the lowest class of organized bodies"...... those were the words of Sir Richard Owen 180 years ago. He was referring to Euplectella Aspergillum, the deep sea glass sponge popularly known as Venus's Flower Basket. With the help of a neatly drawn diagram, he went on to describe minutely and meticulously the physical features of the sponge for the benefit of the learned members of the Zoological Society of London. The hand drawn black and white diagram captures in full the intricate geometry of the object and can compete with the best digital photograph of today . The presentation was later published in a subsequent issue of the Society's journal. And it is indeed a pleasure to read that paper.(see reference 1)

Venus' Flower Basket

The secret of this sponge's etherial beauty obviously lies in its glassy skeleton. The skeleton is composed of spicules of amorphous hydrated silica . And where does the silica come from? From the sea water of course. Sand (Silicon dioxide) reacts slowly with sea water, to yield Silicic acid (H4SiO4). The sponge has specialized cells which secrete an enzyme Silicatein, which extracts pure silica from silicic acid and facilitates its assembly into spicules. The resultant glass fibre has an inner core of spicules wrapped in concentric layers of silica and organic matter are woven together to form a fine mesh of alternating holes and squares. The structure has superior mechanical strength, can withstand with elegance the high speed ocean currents, and various types of mechanical stresses, without fracturing. In case a crack is develops in the outer layer, it remains localised because the layered structure prevents inward propagation of the crack. Thus primitive though the organism might be, it is equipped with state of the art technology to build a glass fibre skeleton sturdy, beautiful and functional.

Prof Joanna Aizenberg at the Harvard University and her team from Bell Laboratories were amazed to find the striking similarities between the sponge skeleton and modern optical fibers. The glass skeleton is structurally and functionally more advanced in comparison to the man-made optical fibers. On top of that while we need high temperature to manufacture optical fibers, the primitive sponge mocks at us by achieving it at the cold temperature of the ocean bed.

The sponge is a kind of water pump as well. It sucks in water through the lateral pores and then vents it out from the top. To model this fluid flow Falcucci et al needed to run advanced algorithms at the High performance computing Center, Cineca, Italy. Upon simulation they found nutrient rich swirls being generated within the body cavity of the sponge which facilitates food filtration while the external ridges reduce hydrodynamic drag and increase the residence time of the fluid inside. Being aware of the implications of this finding in high riser architecture, Falcucci is excited : "Will there be less aerodynamic drag on high-rise buildings built with a similar lattice work of ridges and holes?Will it optimise the distribution of forces applied?"

REFERENCES:

1.Description of a new genus and species of sponge Euplectella Aspergillum,O

2. Biological glass fibers: Correlation between optical and structural properties: Aizenberg et al., Proc.Natl.Acad.Sci. 101, 3358-3363 (2004)

3. Fibre-optical features of a glass sponge

4. Marine sponges inspire the next generation of skyscrapers and bridges

5.How intricate Venus’s-flower-baskets manipulate the flow of seawater

6. Extreme flow simulations reveal skeletal adaptations of deep-sea sponges: G. Falcucci et al.Nature 595, 537-541, 2021.