Three NAKED facts
NF#1: Sponges are animals! It's OK if you thought sponges were plants. In fact until about 100 years ago, early scientists also considered them to be plants.
NF#2: Sponges vacuum food out of the water. A sponge sucks water into its body and traps edible bits in the water flow. A sponge can filter water many times its body volume in a short time. In general, a sponge can pump water equal to its body volume once every 5 seconds!
NF#3: Sponges are not softies: Although they look soft and are generally immobile, sponges are not as defenceless as they appear. Many sponges have tiny hard spikes throughout their body. Some spikes are like glass needles. In addition, some sponges release chemicals that irritate other creatures (including other sponges) and prevent them from growing over the sponges. Others contain chemicals that taste bad or are toxic, so animals won't nibble on them.
Some sponges might give you a rash. So please don't touch the sponge!
(Possible Visitor Question: But what about bath sponges? The natural bath sponge is a special kind of sponge that does not have nasty spikes. )
In fact, sponges are so well defended that small animals may live inside and on a sponge. These animals also get free 'air-con' from the flow of water generated by the sponge!
Interactive activity: let's see what animals live on this sponge?
This brown sponge is quite commonly seen on Sentosa. It is usually riddled with tiny brittlestars, one brittlestar in each hole, with only its tiny hairy arms sticking out. During the day, however, the brittlestars are usually well hidden and it's hard to see them.
Too Much Information
Besides Naked Hermit Crabs, ordinary people probably won't soak up this information like a sponge (oops...spontaneous corny joke).
A sponge is a simple animal made up of a few types of cells. These cells are largely independent of one another and only loosely held together. These cells do not form tissues or organs, so a sponge does not have a mouth, digestive system or circulatory system.
A sponge is NOT a colony! In the way that a hard coral is a colony of individual animals.
Why are sponges so colourful?
Scientists don't really know why. One suggestion is that the vivid colours of some sponges warn of their toxic or distasteful nature. The colours might also be a kind of sunblock that protect from harmful rays of the sun. Some sponges harbour symbiotic algae that may colour them green, violet or brown.
Some sponges commonly seen on Sentosa
A yellow to brownish sponge with several 'cones'. When out of water, the cones collapse into mounds. If you come across a large submerged sponge, look for the tell-tale signs of the current of water generated by the sponge.
This encrusting sponge can cover an area of 20-40cm of coral rubble and other hard surfaces. Sometimes branches from out of the encrusting base. The surface of the sponge has prickles. It may be yellow, orange, brown or greenish.This sponge resembles a pot! Usually somewhat oval and squat with one or more depressions in the centre, and lumps on the outside. May be yellow, orange or brown.
This sponge forms a smooth layer over coral rubble with irregular bumps and ridges. It has tiny holes. It is usually blue, sometimes violet or greenish.This tiny pink puff (1-2cm) is a sponge! Usually one or two on coral rubble.