Discovery of Giant Roaming Deep Sea Protist Provides New Perspective on Animal Evolution
Biologist Mikhail “Misha” Matz and his colleagues recently discovered the grape-sized protists and their complex tracks on the ocean floor near the Bahamas. DNA analysis confirmed that the giant protist found by Matz and his colleagues in the Bahamas is Gromia sphaerica, a species previously known only from the Arabian Sea.
Matz says the protists probably move by sending leg-like extensions, called pseudopodia, out of their cells in all directions. The pseudopodia then grab onto mud in one direction and the organism rolls that way, leaving a track. Hr says the giant protists’ bubble-like body design is probably one of the planet’s oldest macroscopic body designs, which may have existed for 1.8 billion years.
“I personally think now that the whole Precambrian may have been exclusively the reign of protists,” says Matz. “Our observations open up this possible way of interpreting the Precambrian fossil record.”
He says the appearance of all the animal body plans during the Cambrian explosion might not just be an artifact of the fossil record. There are likely other mechanisms that explain the burst-like origin of diverse multicellular life forms.
A distant relative of microscopic amoebas, the grape-sized Gromia sphaerica was discovered once before, lying motionless at the bottom of the Arabian Sea. But when Mikhail Matz of the University of Texas at Austin and a group of researchers stumbled across a group of G. sphaerica off the coast of the Bahamas, the creatures were leaving trails behind them up to 50 centimeters (20 inches) long in the mud.
The trouble is, single-celled critters aren’t supposed to be able to leave trails. The oldest fossils of animal trails, called ‘trace fossils’, date to around 580 million years ago, and paleontologists always figured they must have been made by multicellular animals with complex, symmetrical bodies.