Anaerobic multicellular organisms

Roberto Danovaro and his team from Polytechnic University of Marche, Italy, have discovered the world’s first known multicellular anaerobic (non-oxygen using) organisms. The creatures are as yet unnamed specimens from the phylum Loricifera. The microscopic creatures were found in the deep L’Atalante basin of the Mediterranean Sea. This basin is so salty and dense that the deep waters do not mix with the oxygenated waters closer to the surface.

The researchers proved that the organisms were metabolically active by observing their uptake of radioactive tracers. Unlike other multicellular creatures, the new specimens appear to completely lack mitochondria, but instead have organelles called hydrogenosomes, hitherto found only in single-celled obligate anaerobic organisms. Whereas mitochondria utilize oxygen as an energy source, hydrogenosomes use hydrogen.

Light microscopy image of the undescribed species of Spinoloricus, phylum Loricifera (stained with the protein-binding stain Rose Bengal) The bright pink cap is about 150 µm (ten thousandths of a centimeter) in length.

Image Credit: R. Danovaro et al., BMC Biology

This discovery could shed light on the development of multicellular creatures on the early Earth before oxygen was plentiful.

Hat tip: The Skeptics' Guide to the Universe.