The Web of Life (401-4) Xenophyophores


While the term microbe entwines tiny, not all unicellular organisms are microscopic. Deep in the ocean trenches, on abyssal plains, up to 10.6 km down, live xenophyophores: single-celled protozoans, some 42 known species, that grow to 20 cm in diameter. These are ancient creatures, dating to the Ediacaran (635–542 MYA).

Xenophyophores are delicate; basically, lumps of viscous fluid – cytoplasm – with numerous nuclei evenly distributed throughout. Their bodily sprawl is contained in a ramose (branched) system of tubes called a granellare, made of an organic cement-like substance.

Xenophyophores are tireless bottom feeders; rooting through sea floor mud for unknown nutrition. But what is known is that what goes in comes out as slime.

This fecal matter, termed stercomes, mixes with their secreted cement to form stercomares: structures which agglutinate around the granellare, further augmented by scavenged minerals and the microscopic remains of other organisms, such as sponges. The shell inside a stercomare is termed a test.

Out of the mud comes a high-rise. Stercomares are a habitat for worms, clams, sea stars, and crustaceans.

By this, xenophyophores are benthic beavers: creating a conducive environment for other species. Besides building stercomares, xenophyophoric foraging stirs the sediment, releasing nutrients that others appreciate.

Xenophyophores prolifically live in all the oceans; indispensable agents for engendering diversity in benthic ecosystems. A single cell can make a difference in the world.