Hexactinellid
From Freepedia
Hexactinellid sponges are sponges with a skeleton made of four- and/or six-pointed silaceous spicules, often referred to as 'glass sponges'. Hexactinellids are relatively uncommon nowadays and are mostly found at substantial depths. There are big differences between hexactinellids and other sponges. They are often cup-shaped animals with sturdy internal skeletons made up of fused spicules. Much of their body tissues are syncitia, extensive regions of multinucleate cytoplasm. They are fairly common relative to Demosponges as fossils, but this is thought to be at least in part because their spicules are sturdier than spongin and fossilize better. Unlike other sponges, they do not possess the ability to contract.
One ability they do possess is a unique system for rapidly conducting electrical impulses across their bodies, making it possible for them to respond quickly to external stimuli. Hexactinellids like the “Venus Flower Basket” have a tuft of fibres that extends outward like an inverted crown at the base of their skeleton. These fibres are between 50 and 175 mm long and about the thickness of a human hair. They work as fibre optics that are surprisingly similar to the fibres used in modern telecoms networks and could even be more handy than the man-made versions. The biological fibres of the sponge conduct light beautifully when they are illuminated, and are use the same optical principles that modern engineers use to design industrial fibre optics.
Despite not having the ultra-high transparency needed for telecoms networks, they do have other advantages; unlike commercial fibre, it is possible to tie them in tight knots without them cracking or breaking. Another advantages is the fact that these biological fibres are produced by chemical deposition at the temperature of seawater. For the moment, human fibre optics can only be produced with a high-temperature furnace and expensive equipment. The earliest known hexactinellids are from the earliest Cambrian or late Neoproterozoic.
