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| Read more about sea sponge biodiversity. |
If you ride on a boat that has a glass window in the bottom of it, you can look down into the water and see many strange creatures and plants. Of course you notice a great many fishes swimming about, probably in search of food. If the water is not too deep, you may see some lobsters, crabs and shell-fish lying on the sandy bottom or moving among the rocks. Your boat may reach waters in which the star-fish and sea urchins live and jelly-fish float like tiny opened umbrellas.
Among all of these strange creatures, there are some that seem like flowers growing under water, with stalk or root fixed to some solid object. You may be looking at sea lilies and sea anemones; and many of the plant-like creatures you notice may be sponges. Perhaps you think that all these animals are plants because they do not swim or crawl like other water animals. Some of them do not seem to eat or breathe; and yet they remain alive and grow large. Scientists watch these creatures through magnifying glasses and find that they really do eat and breathe and act much like other animals even though they are rooted to one place during the greater part of their lives.
Let us watch a sponge and see how that strange water animal carries on its life. A young sponge may develop in one of two ways. It may grow as a small bud on a large rooted sponge; and then break off, settle on some solid object and remain attached during the rest of its lifetime. The small budding sponge is much like the larger one; and continues to grow until it reaches the size of the original sponge.
Professor Joeseph Pawlik from
University of North Carolina, Wilmington
talks about sea sponges.
A young sponge may develop in a more complicated manner than by budding. It may begin as a bit of matter protected by the parent sponge until it develops swimming paddles. These are long hair-like flagella extending from the round body; and are used to whip the water into motion. After the tiny creature swims away from the full-grown sponge, it changes from its rounded form to cup-shape. In a short time a kind of outer skin begins to cover the flagella. The young sponge, now unable to swim, attaches itself by the rim of the cup to a solid object. There it remains; and develops typical sponge habits, absorbing food and oxygen from the water which circulates through its body. In four or five years it is as large as the original parent sponge.
A sponge is indeed an odd creature, with no head or legs and not even a backbone. It has a solid fleshy body, with small pores all over the outside and a larger pore near the top of the sponge. The small pores are the mouths of hollow tubes which lead in to the center of the body; and the large pore at the top is the end of the stomach or internal cavity.
It is hard to believe the sponge is really alive until you see it spouting water from its eye as the fishermen call the large pore. If you could see inside the sponge you would be astonished by its activity. Water enters the sponge body through the small pores. The hair-like flagella which once helped the baby sponge to swim are now turned toward the inside; and each waves regularly. Together the flagella beat the water into whirlpools and then force it out of the sponge. Bits of living matter and oxygen in the water are absorbed during this circulation from small pores to large; and thus the sponge lives and grows.
Sponges are found in all the seas of the world and even in some of the lakes. Some of them grow best in shallow water and others live so far under the surface that only deep sea divers can find them. Sometimes they grow together in colonies; and it is almost impossible to separate individual sponges. They range from a pin-head in size to the height of a man; but most of them are about the size of a large cake. Yellowish-brown is the favorite color; but practically every shade of the rainbow can be found.
Sponges take such interesting shapes that people name them for resemblance to familiar objects. Many of them resemble vases; and one beautiful white sponge is called Venus's flower basket. A number of sponges take the shape of cups; and one immense sponge is called Neptune's goblet. Sponges that grow in deep water often develop long branch-like fingers.
A sponge can live for a long time; and it does not always die even when it is cut in two. People who sell sponges sometimes catch a full-grown living sponge, cut pieces from it and throw them all back into the water. The original sponge will continue to live; and each cut piece will grow larger and in a few years there will be several full-size sponges instead of one. Since a sponge is a water animal it will die if it is allowed to become thoroughly dry. The soft fleshy parts which caused the living sponge to feel slimy, gradually disappear and the skin shrivels and falls off. All that is left of the sponge is the skeleton. Some sponge skeletons are hard like flint or stone and are never used for the market. The soft and horny skeletons, however, are sold for bath sponges, desk sponges and other purposes. The skeleton of a sponge resembles the living animal more than do the skeletons of most other animals. Fisher
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