Eldon Hemminger, age 11, of Winnipeg, Manitoba, Canada, for his question:
What are radiolarians?
Their name means minor sunbeams, because their delicate skeletons radiate in such delicate designs. So far, almost 5,000 radiolarians have been identified, each one a tiny jewel. Most of them are microscopic in size and too small to be seen. But a few species span a fifth of an inch. All of these mini gems are single celled animals of the protozoan group.
The radiolarians are at home in the plankton rich waters of the salty sea. They share this realm with teeming multitudes of single celled algae, mini copy pods and dainty diatoms, plus swarming populations of the eggs and larvae of assorted sea dwellers. Most of the plankton populations are invisibly small. But together they form a rich seafood salad. This is. the first link in the food chain that feeds the hungry ocean.
The 5,000 or so radiolarian species are merely single celled blobs of cytoplasm. But almost all of them are talented builders and their artwork often survives through hundreds of millions of years, long after the living builders have departed.
Their building material is silica, the mineral used to make the hardest of the earth’s common rocks. Silica is dissolved in seawater and the radiolarians extract it, molecule by molecule, to build delicate lattices around their soft little bodies. Many of them build openwork spheres, often with one lacy ball inside another. Some are dainty saucers and others look like lacy caps or helmets. In many species, the tough silicon designs look like little bells.
Naturally, each species inherits a family blueprint and builds a perfect copy of the design used by its ancestors, way back into antiquity. The tough lacy shells protect the soft bodies within and the holes allow them to poke forth sticky fingers called pseudopods. They do this to catch passing diatoms, copy pods and other smaller than small plankton dwellers. The victims are trapped when two or more sticky pseudopods grab them and stuff them down inside to be digested.
The soft body of the average radiolarian has an outer layer of frothy material which seems to help him to select his preferred water level. Most species live 600 feet or so below the waves and some go down as far as three miles. However, many live just below the surface where sometimes the sun is too hot and the waves too rough for comfort. This is when a surface dwelling radiolarian releases his watery bubbles and sinks below until things improve.
The radiolarians prefer warm or tropical seas—and we know they have lived there for countless ages. When they die, their durable little skeletons sink to the bottom. In the Indian and Pacific Oceans, some three million square miles are covered with radiolarian ooze. This is a mixture of slimy mud and tough radiolarian shells that have endured through several hundred million years.