This allows them to 'feed' symbiotic photosynthetic micro-organisms that live deep within their bodies. The sponge's 'fibre optic cable' is its spicules.
How do sponge create their spicules? An intriguing question that has been much studied.
In 2005, a study reported some breakthroughs. The report also highlighted some thought-provoking facts:
Nature produces silica on a scale of gigatons –– thousands of millions of tons –– thousands-fold more than man can produce. This biosynthesis is remarkable because this nanoscale precision can't be duplicated by man. Besides this remarkable precision, nature manages to produce silica at a low temperature, in an environmentally friendly way without the use of caustic chemicals, whereas man must use very high temperatures, high vacuums, and dangerous chemicals requiring costly remediation.We have a lot to learn from nature and our biodiversity.
Nature's 'fibre optics' experts
Matt Walker, BBC News 10 Nov 08;
Sea sponges can beam light deep inside their bodies, and do so using the natural equivalent of fibre optic cables, scientists have found.Light Inside Sponges: Sponges Invented (and Employed) The First Fiber Optics
Sponges are among the oldest and simplest of Earth's animals. The discovery that they use such a futuristic light transmission system has therefore delighted researchers.
The finding, made by a German team, is published in the Journal of Experimental Marine Biology and Ecology.
Whereas other animals pass electrical currents around their bodies using nerve cells, sponges appear to be the only animals capable of transmitting light around their bodies in this way, the group says.
This may help explain why some sponges are able to grow so big, and also clear up a long-standing mystery about how other, much smaller organisms are able to live deep within the bodies of large sponges.
Glass skeletons
Sponges mainly live in the sea, and are extremely primitive organisms. They lack muscles, nerves and internal organs, for example, and are essentially a diverse set of cells supported by a hard exoskeleton.
Two of the three major types of sponge build their skeletons using special structures called spicules. These are made from silica and are basically glass rods. Previous experiments suggested that light can pass along these structures.
Now, Franz Brummer, of the University of Stuttgart, and colleagues have proved that living sponges use these internal glass rods as light conductors.
Light reaching the surface of the sponge is reflected off the insides of each spicule in much the same way light bounces along the inside of a fibre optic cable used to transmit electronic data. In doing so, light is beamed deep into the sponge.
Brummer's team made the discovery using living sponges of the species Tethya aurantium . They collected the sponges from shallow waters off the coast of Croatia, and then transferred them to tanks of seawater.
They then implanted light sensitive paper deep inside each sponge. They did so under dark conditions and then exposed the surface of the sponge to light. When they checked the paper, they found it was covered in spots, which corresponded exactly with where light would exit each spicule.
Shared existence
In a control experiment, the researchers tested another sponge that does not grow using glass spicules. No light entered deep within it, showing that spicules are necessary to transmit the light.
"Sponges are fascinating animals and there're lots about them we are waiting to discover," says Brummer.
He suspects that deep-sea sponges may use giant natural fibre optic arrays to harvest what little light reaches them. "Sponges in the deep sea can form spicules up to one metre long and two centimetres in diameter," he explains.
Beaming light deep inside their bodies may explain why some sponges grow to such large sizes, and develop rounded shapes.
To grow big, sponges need essential nutrients, including carbon, nitrogen and other metabolites. These are provided by smaller organisms such as algae and cyanobacteria, with which the sponges have a symbiotic relationship.
But these smaller organisms need light to survive. Because of this they usually live on the outside of sponges.
In 1994, however, researchers discovered that algae sometimes do live deep within the bodies of sponges, creating a mystery as to how they survive there. The answer, as Brummer's team has now confirmed, is that they live off light beamed down to them.
ScienceDaily 19 Nov 08;
Fiber optics as light conductors are obviously not just a recent invention. Sponges (Porifera) -- the phylogenetically oldest, multicellular organisms (Metazoa) -- are able to transduce light inside their bodies by employing amorphous, siliceous structures.
Already more than ten years ago, the finding of photosynthetically active organisms inside sponges raised the question, how they could survive there in an otherwise presumably dark space. Already at that time, the marine biologists Elda Gaino and Michele Sarà from Genova, Italy, hypothesized, that light might be transferred inside the sponge body.
Marine zoologists from the University of Stuttgart, and from the Leibnitz Institute for Marine Sciences at the University of Kiel, both within the research project BIOTECmarin, could now show, that the siliceous skeletal elements (spiculae) of the marine sponge Tethya aurantium in fact can transduce light, and do so in living sponges.
Three of the numerous needle bundles in Tethya are shown here. (Credit: University of Stuttgart / Zoology)Sponges without those spicules -- like the aspicular sponge Aplysina aerophoba -- are not able to transport light inside their tissue. In their latest research, the scientists from Stuttgart and Kiel are the first to demonstrate light transduction inside living sponges. Until now light transduction could only be shown in explanted single spicules after laser illumination.
The authors Franz Brümmer, Martin Pfannkuchen, Alexander Baltz, Thomas Hauser and Vera Thiel published these exciting results in the Journal of Experimental Marine Biology and Ecology with the title: Light inside sponges.
Marine sponge yields nanoscale secrets
This may have hi-tech applications, report UCSB scientists
EurekAlert 24 May 05
(Santa Barbara, Calif.) –– The simple marine sponge is inspiring cutting-edge research in the design of new materials at the University of California, Santa Barbara.
A report about these exciting new results involving the use of gold nanoparticles is the cover story of the current issue of the scientific journal, Advanced Materials. The article is written by Daniel E. Morse, professor of molecular, cellular and developmental biology at UCSB, and director of the Institute for Collaborative Biotechnologies, and his research group. The authors include postdoctoral fellow, David Kisailus (first author), and graduate students Mark Najarian and James C. Weaver.
The simple sponge fits into the palm of your hand, and proliferates in the ocean next to the UCSB campus, said Morse. "When you remove the tissue you're left with a handful of fiberglass needles as fine as spun glass or cotton. This primitive skeleton supports the structure of the sponge, and we've discovered how this glass is made biologically."
The newly reported research describes an important step forward in translating nature's production methods in the biological world into practical methods for the development of new materials in the laboratory.
The research team developed a method for coupling small, inexpensive synthetic molecules (that duplicate those found at the active center of the bio-catalyst of the marine sponge) onto the surfaces of gold nanoparticles. They showed that when two populations of these chemically modified nanoparticles, each bearing half of the catalytic site, are brought together, they function just as the natural biological catalyst does to make silica at low temperatures.
The UCSB scientists are already taking the next steps toward the development of practical new and useful methods of nanoscale production by incorporating catalytic components on the flat surfaces of silicon wafers, using these techniques to create nanoscale patterns of their catalyst. They are learning how to write nanoscale features of semi-conductors on these chip surfaces.
A few years ago, Morse and his research group began investigating how nature builds materials from silicon. Silicon is particularly interesting to Morse, because it is considered by many to be the most important element on the planet technologically. Silicon chips are fundamental components of computers and telecommunications devices. In combination with oxygen, silicon forms fiber optics and drives other high-tech applications.
Morse explained that his research group discovered that the center of the sponge's fine glass needles contains a filament of protein that controls the synthesis of the needles. By cloning and sequencing the DNA of the gene that codes for this protein, they found that the protein is an enzyme that acts as a catalyst –– a surprising discovery. Never before had a protein been found to serve as a catalyst to promote chemical reactions to form the glass or a rock-like material of a biomineral. From that discovery, the researchers learned that this enzyme actively promotes the formation of the glass while simultaneously serving as a template to guide the shape of the growing mineral (glass) that it produces.
These discoveries are significant because they represent a low temperature, biotechnological, catalytic route to the nanostructural fabrication of valuable materials. Nature produces silica on a scale of gigatons –– thousands of millions of tons –– thousands-fold more than man can produce, said Morse. "This biosynthesis is remarkable because this nanoscale precision can't be duplicated by man."
Besides this remarkable precision, nature manages to produce silica at a low temperature, in an environmentally friendly way without the use of caustic chemicals, whereas man must use very high temperatures, high vacuums, and dangerous chemicals requiring costly remediation.
Although the reported research marks an important step forward, Morse believes that the use of these biological methods to control such syntheses would be impractical on an industrial scale. The high cost of the purification of these proteins, the requirement of the proteins for a watery environment, and their instability, all make their incorporation into electronic devices impractical. Furthermore, the presence of proteins would be incompatible with the high electronic performance required for today's device applications.
Instead, the scientists expect that by learning the fundamental mechanism used in nature, that mechanism could be translated into a practical and low-cost manufacturing method. Such a "biomimetic" approach will eventually be used in industry, said Morse.
