Parakaryon

Lore & Background

The only known specimen of Parakaryon myojinensis was collected from the bristle of an unidentified scale worm living at hydrothermal vents on Myōjin Knoll, about 1,240 meters deep in the Pacific Ocean. The specific name myojinensis reflects this location. The generic name Parakaryon comes from Greek words meaning 'beside' or 'beyond' and 'nucleus', highlighting its distinction from both eukaryotes and prokaryotes.

Reader's Guide

Parakaryon myojinensis is significant because it challenges the traditional division of cellular life into prokaryotes and eukaryotes. Its discoverers proposed that it is not simply a case of bacteria living inside another prokaryote, citing reasons such as the presence of multiple bacterial species in a single host, the orderly cellular structures without signs of digestion, and the improbability of dense predator-host populations at the collection site. However, only one specimen has ever been found, preventing further study through culturing or DNA sequencing. British evolutionary biochemist Nick Lane hypothesized that this organism could be the first known example of symbiogenesis outside eukaryotes, potentially offering clues about the development of complex life. Later studies of bacteria from the same location found instances of intracellular bacteria within dead bacteria, but the authors continued to treat Parakaryon myojinensis as a valid taxon.

Did You Know?

• Parakaryon myojinensis is known from only a single specimen, described in 2012.
• It has structural features unique to eukaryotes, some unique to prokaryotes, and some different from both.
• The specimen was collected from a scale worm at hydrothermal vents on Myōjin Knoll, about 1,240 meters deep in the Pacific Ocean.
• British evolutionary biochemist Nick Lane hypothesized it could be the first known example of symbiogenesis outside eukaryotes.