Monday Brain Fodder: Light-Conductive Skeletons

Cabinet of Wonders


(“Hexactinellae” from Ernst Haeckel‘s Kunstformen der Natur, 1904)

The Venus Flower Basket is a type of hexactinellid sponge found in deep ocean waters.  Here’s what Wikipedia says about them:

“The glassy fibers that attach the sponge to the ocean floor, 5-20 cm long and thin as human hair, are of interest to fiber optics researchers. The sponge extracts silicic acid from seawater and converts it into silica, then forms it into an elaborate skeleton of glass fibers…

These sponges’ skeletons have amazing geometric configurations, which have been extensively studied for their stiffness, yield strength, and minimal crack propagation. An aluminum tube (aluminum and glass have similar elastic modulus) of equal length, effective thickness, and radius, but homogeneously distributed, has 1/100th the stiffness.”

Not only that, but the spicules, the (sort of) hairs of the animal, consist of a fine silica glass thread covered with a reflective coating, just like fibre optic thread, but thinner — and so flexible that they can be tied into a knot without breaking.  Unlike man-made glass fibres, they are formed at normal temperatures, allowing the sponge to build the spicules out of the very specific chemicals that make it so able to carry light — something scientists wish they could reproduce.

One last weird thing about these sponges:  “the majority of their soft tissue is made of a giant multinucleated cell, not individual cells like other animals. Because of this, at least one species can send electrical signals through the whole animal, in the same way that signals travel through nerves. These signals are typically in response to touch or to sediment in the water. The signal reaches all parts of the sponge and causes the sponge to stop filtering water. After a few minutes, the sponge will start its filtering again, but if the irritation is still there it will stop again, and it will keep testing the water in this way until the water is clear of sediment or the disturbance has gone.”
(– Glass Sponges and Sponge Reefs in BC Waters, by Dr. Sally Leys, University of Alberta)

Lastly, although their skeletons are made of silica (glass), they are still flexible.  How do they do that?

I can’t help but wonder: what if, through genetic manipulation, glass sponges are able to build things for us? Armor, architecture and lightweight, strong vehicle panels — all of which can also be used to communicate information via their spicules…

More on sponges in general, and glass sponges in particular (about halfway down).

Also, a video about the brilliant strength and structural design in glass sponges.

 

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