Most of us think of sponges as everyday household items. Their softness and absorbency make them versatile tools for cleaning our bodies, floors, and dishes, and for applying paint to our walls. Although the sponges we use today are likely to be made of synthetic materials, for most of human history we harvested our sponges from the oceans—the dried bodies of aquatic invertebrates.
Sponges can be found in marine environments throughout the world, from lakes and rivers to vast oceans, and from warm tropical climates to icy polar regions. They come in various shapes and sizes, with astoundingly vivid colors and intricate structural architecture. The underwater equivalent of flowers, their beauty is truly breathtaking. But although they may look like plants, sponges are members of the animal phylum Porifera (“pore-bearing”). Because sponges are among the simplest of multicellular animals, evolution-based science relegates them to the lowest branch of the animal “family tree.” Yet these simple animals are not so simple. Sponges are a remarkable example of God’s creative brilliance.
Unlike most animals, sponges have no external or internal organs or muscles. They lack circulatory, nervous, and digestive systems. Sponges rely on cellular specialization to perform the functions necessary for life.
Some sponges are soft and fibrous. Others have a more rigid, yet highly flexible, skeletal frame that can withstand powerful ocean currents. Cells called sclerocytes secrete calcite or silica strands of varying lengths to form these deceptively delicate architectural wonders. Researchers are studying sponges’ construction techniques to find ways to help human engineers erect “taller, stronger, and more flexible buildings” (“Secrets of Our Ocean Planet: Sponges as Civil Engineers and Pharmacists,” blog.NationalGeographic.org, April 24, 2018).
The body of a sponge is a hollow, open chamber, with a jelly-like substance called mesohyl between inner and outer layers of cells. A thin skin of plate-like cells, pinacocytes, forms the outer layer. Cells known as choanocytes form the inner layer. Choanocytes have a funnel-like collar covered with sticky hairs, surrounding a central flagellum.
A sponge’s outer layer contains many tiny pores, which connect to the inner layer to form a complex network of channels through the mesohyl. Choanocytes line the walls of these channels. The flagella of the choanocytes move back and forth in unison, directing the flow of water through the network of canals. The sticky hairs of the choanocytes capture particles of organic matter carried in the water, and mobile amebocyte cells engulf and transport these captured bits to other cells within the sponge.
The filter-feeding of sponges has a positive impact on the water quality of marine ecosystems. As they feed, sponges clean the water by removing harmful bacteria, pesticides, and in some cases, even heavy metals such as tin and lead.
They do this extremely efficiently and effectively. Sea sponges are known to remove more than 90 percent of the bacteria and organic matter found in the water they process (“Denizens of the Deep: How Sponges Create Important Habitats,” Marine Conservation Institute, January 22, 2019). As reported in Horizon: The EU Research & Innovation Magazine, “Every day, a sea sponge can filter between two and 20 cubic metres of water per kilogram of body weight, and researchers are studying the possibility of using them on an industrial scale in a process known as bioremediation—where organisms are used to remove pollutants” (“The cleaning power of sea sponges,” January 6, 2016).
The sponge stores within itself anything removed from the water that is not consumable as food. The jelly-like mesohyl of a sponge is home to a host of live bacteria, viruses, and toxins, making the animal of enormous interest to medical researchers for its pharmacological potential.
Laboratories around the world have engaged in a fascinating experiment involving sponges: When they separate the individual cells of a live sponge, they find that the cells will reassemble to form one or more smaller sponges. The disassociated cells of a sponge can aggregate and reconstruct its entire body. Sponge cells do not require an assembly order, so a sponge can rapidly regenerate if forcibly separated. If two different species of sponge are put through a sieve together, the separated cells will sort themselves and combine only with other cells of the same species.
Given a food-rich environment, individual sponge cells could survive simply by reverting to an amoeba-like state. However, that is not what they do. They rebuild. As they reconstruct the original animal, the cells of these simple animals display knowledge, intent, and the ability to identify other cells as part of the original larger sponge. Amazingly, sponges do this without an apparent means of communication, and despite having neither a brain nor a central nervous system. And scientists do not fully understand the mechanism by which sponges accomplish all of this. Carried somehow within each cell of this “simple” creature are the necessary blueprints and instructions—including knowledge of all the specialized cells and cellular functions required for life—to work with other cells and build another complete sponge.
Astounding as this is, there is even more to the sponge’s amazing ability to regenerate. Sponge cells—sclerocytes, pinacocytes, choanocytes, amebocytes, and other cells of a sponge—are all totipotent. That is, each sponge cell is similar to a stem cell, able to become a different kind of cell. Therefore, sponges can change the function of every cell in their body when necessary (“Secrets of Our Ocean Planet: The Not-So-Simple Sea Sponge,” blog.NationalGeographic.org, April 23, 2018). When strong currents damage it, or a hungry fish bites it, or a part of it is harvested for a bath scrub, the sponge can heal itself—because any cell near the damaged area can take on the cellular specialization of the injured or missing cells.
Although they are scientifically classified as simple multicellular animals, we can appreciate that sponges are not so simple! Their form and structure, their ability to clean their ecosystem, and their miraculous ability to regenerate attest to a complexity far beyond human understanding. These fantastic creatures are ideally suited to their environment and their role. The ingenious perfection on display in the sea sponge cannot be the result of mere chance and natural processes. It is evidence of a Creator who has planned, designed, and built everything needed to sustain life on this planet.
No wonder King David was inspired to write, “O Lord, how manifold are Your works! In wisdom You have made them all. The earth is full of Your possessions—this great and wide sea, in which are innumerable teeming things, living things both small and great” (Psalm 104:24–25).