Sponges Not Softies: Although they look soft and are generally immobile, sponges are not as defenceless as they appear. They have a skeleton made up of a framework of spicules (tiny, hard spikes) throughout their body. These spicules are often sharp and needle-like. These provide support, keeping the sponge upright and their canals open. Spicules also gives them a rough texture and makes them an unpleasant mouthful. Most have spicules made up of silica, the same substance that glass is made of. Some sponges release chemicals which irritate and deter other creatures (including other sponges) from growing over them. Others produce toxins or foul-tasting chemicals to deter sponge-eaters. In fact, some sponges on Chek Jawa might give you a rash. So avoid handling them. Living in a sponge: With its natural defences and a constant flow of water through it, a sponge is a safe, well-oxygenated home for tiny creatures. A large sponge may be home to a vast number and variety of such tiny animals that live in the labyrinth of canals and chambers inside the sponge. These include crabs, brittle stars, synaptid sea cucumbers and tiny snapping shrimps. Besides finding shelter, some creatures may eat larger particles that accumulate on the sponge surface. It is said that some may even feed on substances produced by the sponge. Larger animals may also exploit sponges for protection. For example, the Velcro crab and Sponge crab use sponges for camouflage. Human uses: Today, the sponges you use at home are synthetic and not made from living sponges. In the past, natural sponges were used in the same way, e.g., for padding and packing, to paint with and to bathe with. The sponges used for these purposes have a skeleton made up mostly of a soft protein called spongin rather than prickly spicules. Nowadays, living sponges have become important as potential sources of new medicines. The toxins and foul-tasting substances that sponges have developed to defend themselves are being studied for medical applications such as new antibiotics. Status and threats: Sponges are threatened mainly by habitat loss. They are also affected by pollution and activities that increase sedimentation in the water. Please don't break the sponges. They take time to regrow and are homes to other animals. Some sponges may also cause skin irritation.

Some of the tiny creatures that live in sponges A tiny sea cucumber A tiny shrimp Another tiny shrimp A tiny brittle star The arms of tiny brittle stars hidden in a sponge

• Lim, S., P. Ng, L. Tan, & W. Y. Chin, 1994. Rhythm of the Sea: The Life and Times of Labrador Beach. Division of Biology, School of Science, Nanyang Technological University & Department of Zoology, the National University of Singapore. 160 pp.
• Tan, Leo W. H. & Ng, Peter K. L., 1988. A Guide to Seashore Life. The Singapore Science Centre, Singapore. 160 pp.

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