TW Viewpoint | Sea Sponges and Unity

September 12, 2018 | Gary Molnar

Sea sponges are considered to be some of the simplest of multi-cellular animals on earth. They have neither a central nervous system nor a brain yet the various types of cells within a sea sponge are able to perform the many different functions necessary for life.

Subscribe Today! If you would like to receive weekly emails informing you when new commentaries and Tomorrow's World Viewpoint videos are uploaded, please subscribe to our e-newsletter.

". . . A sponge is covered with tiny pores, called ostia, which lead internally to a system of canals and eventually out to one or more larger holes, called oscula. Within the canals of the sponge, chambers are lined with specialized cells called choanocytes, or collars cells. The collar cells have a sticky, funnel-shaped collar and a hair-like whip, called a flagellum. The collar cells serve two purposes. First, they beat their flagella back and forth to force water through the sponge. The water brings in nutrients and oxygen, while it carries out waste and carbon dioxide. Second, the sticky collars of the collar cells pick up tiny bits of food brought in with the water. Another type of cell, called an amebocyte, takes the food to other cells within the sponge."

An amazing characteristic of sea sponges is their ability to regenerate. They are able to rebuild parts of their body structure that have been broken off, but it goes far beyond this. There is an interesting experiment that has been performed in laboratories around the world that demonstrates the remarkable regenerative ability of this simple creature. It involves pushing a sea sponge through a sieve:

"Push one through a fine-mesh sieve and its cells will separate from one another, turning the clear aquarium water into a thick, cloudy liquid, like pea soup. Wait a few hours, however, and the cells will gradually find one another, stick together, and reassemble themselves into a whole sponge. Although sponges come in many species, each with distinctive appearance, the individual sponge cells will invariably rebuild the correct architecture for its species. In fact, the disaggregated cells of two different species can be mixed, and the cells will sort themselves out and reassemble only with their own kind, re-creating sponges of the original two species."

Fascinating! Separate the individual cells of a sea sponge and they will recombine to form a sea sponge. They do not form a dog, or a whale, or an ostrich. Once separated, how are the various types of cells, cells that perform different roles, able to recognize and organize themselves into a fully functioning sea sponge? Somehow, inherent within each cell of a sea sponge, are the complete blueprints on how to build a sea sponge as well as the capacity and aspiration to do so. The separated cells of a sea sponge, given the right conditions can survive alone for a limited amount of time, however, rather than remaining alone, they aggregate into a structure that more effectively meets the needs of each individual cell.

Sea sponges may be simple multi-cellular animals but their ability to regenerate is anything but simple. They are a marvelous example of the incredible engineering and design we see all around us.

Watch Sea Sponges and Unity on YouTube at Tomorrow's World Viewpoint