Sponges​—Simple yet Spectacular

BY AWAKE! WRITER IN AUSTRALIA

WOULD you fancy taking a bath with the remains of an animal? The idea may sound less than appealing. However, the natural bath sponge is actually the fibrous skeleton of one such creature.

“Sponges occupy the oldest and lowest branch on the animal family tree,” states National Geographic News. This has led some individuals to speculate that an ancient sponge was the evolutionary ancestor of animals and humans. One television-documentary media release even hailed the sponge as “the animal Eve”​—the “ancestor that started it all for us.”

What has science learned about sponges? Are they merely simple creatures, or do they show evidence of spectacular design?

No Heart, No Brain, No Problem

Sponges may look like plants, but Aristotle and Pliny the Elder accurately described sponges as animals. Experts estimate that at least 15,000 species live throughout the world’s lakes and oceans and include a stunning variety of shapes and colors. Sponges may resemble slender fingers, bulging barrels, spreading carpets, elegant fans, and even delicate crystal vases​—to mention only a few designs. Some are smaller than a grain of rice, while others grow taller than a man. Scientists believe that some sponges may be hundreds of years old.

“In structure, function, and development, sponges are distinct from other animals,” says the Encyclopædia Britannica. How so? Unlike other animals, sponges have no internal body organs. With no heart, brain, or nervous system, how do sponges live? Tiny cells within the sponge care for the many functions that sustain life. Specialized cells catch food, transport nutrients, or remove waste. Others labor to construct skeletal or skin components. Some cells may even switch from one cell type to another should the need arise.

Sponges are unique in additional ways. Mash a live sponge through a sieve, and the cells will group together to reform the original animal. Grind two sponges together, and the cells will gradually separate to reconstitute each original parent. “No other plant or animal can resurrect itself this way,” observes National Geographic News.

Sponges also have remarkable reproductive flexibility. Some sponges equip and launch cellular “spaceships” to colonize other areas. Traveling in a state of suspended animation, the “settlers” finally land, reawaken, and then exit their “ship” to produce a new sponge. Other sponges reproduce sexually, with individual sponges switching between male and female roles as the need arises. Some sponges lay eggs. “The more closely we look at even the simplest organisms, the more complexity we see,” marvels writer Paul Morris.

Marine Vacuum Cleaners

Sponges possess “a feeding system unique among animals,” writes zoologist Allen Collins. Tiny pores in the outer skin lead to a maze of tunnels and chambers that honeycomb the sponge. Millions of tiny rowing cells, or choanocytes, line the walls of this labyrinth. Each cell projects a whiplike filament  that beats backward and forward. “Like oarsmen on a Roman galley, [these cells] propel a steady stream of water past the sponge’s other cells, which are designed to capture and ingest the food particles the water contains,” explains writer Ben Harder. Pumping up to ten times its own volume in water each hour, the sponge extracts nutrients, toxic chemicals, and about 90 percent of all bacteria present in the water. A sponge may even regulate or reverse its pumping  action to compensate for changing water currents or to purge internal sediment. “Sponges are . . . the most efficient vacuum cleaners of the sea,” states Dr. John Hooper.

The constant flow of food and water through a sponge makes it an ideal home for shrimps, crabs, and other tiny creatures. One sponge contained 17,128 residents. Numerous bacteria, algas, and funguses enjoy cooperative, or symbiotic, relationships with sponges. Bacteria may constitute up to 50 percent of a sponge’s wet weight.

Scientists have found sponges and their symbionts to be a promising source of new and unique pharmaceutical drugs. Some believe that such drugs may prove useful in combating AIDS, cancer, malaria, and other diseases. Referring to one such sponge compound, researcher Shirley Pomponi says: “Nature offers much more interesting molecules than even our computers can come up with.”

Crystal Creativity

Unlike the soft and fibrous bath sponge, many sponges are abrasive or rigid. These sponges contain millions of tiny crystals called spicules. When spicules are examined under a microscope, their beauty and variety stagger the imagination. Linked together in various ways, spicules can create intricate skeletons, protective armor, and even cables that measure up to 10 feet [3 m] long and 1/3 of an inch [1 cm] thick. One carnivorous sponge uses Velcrolike fishing nets to catch its prey.

The deep-sea Venus’s flower-basket uses spicules to weave an intricate glass lattice of spectacular beauty. The ultrapure silica fibers closely resemble commercially designed fiber-optic cables. “These bio-optical fibers are extremely tough,” explains one scientist. “You could tie them in tight knots and, unlike commercial fiber, they would still not crack.” How these sophisticated fibers develop in seawater and at low temperatures has scientists baffled. “In this case, a relatively simple organism has a solution to a very complex problem in integrated optics and materials design,” says Cherry Murray of Bell Laboratories.

Chance or Design?

After reviewing the many spectacular biological features evident in sponges, Hooper observes: “The ‘simple sponge’ is in fact a very complex [animal], which even today is not well understood.” It is only reasonable to ask: How and why did this complexity arise. Is mere chance responsible? Or do sponges give eloquent testimony to an intelligent Designer?

Although some may refuse to consider the existence of a Creator, many people will agree with the observation of the ancient psalmist: “How many your works are, O Jehovah! All of them in wisdom you have made. The earth is full of your productions . . . , living creatures, small as well as great.”​—Psalm 104:24, 25.

[Diagram/​Pictures on page 23]

Typical structure of a sponge. Enlarged picture of water-pumping cells

[Picture on page 24]

Sponge spicules

[Picture on page 24]

Venus’s flower-basket

[Picture Credit Lines on page 23]

Sea horse: Rudie H Kuiter; 3 right-hand inset photos: Dr. John Hooper, Queensland Museum

[Picture Credit Lines on page 24]

Top: Eye of Science/​Photo Researchers, Inc.; bottom: Kim Taylor/​Warren Photographic