Parakaryon myojinensis is a single-celled organism known from a single specimen, described in 2012. It has features of both prokaryotes and eukaryotes but is apparently distinct from either group, making it unique among organisms so far discovered.[1]


It is not clear whether P. myojinensis can be classified as either a eukaryote or a prokaryote, the two kinds of organisms known so far. The newly discovered organism has a nucleus and other endosymbionts (organisms living within other cells), so would appear to be a eukaryote. However the nuclear membrane is a single layer, not a double layer as in other eukaryotes, and the DNA is stored in filaments as in bacteria, which are prokaryotes. So this organism has not been classified as either a eukaryote or a prokaryote. Adding to the difficulties of classification, only one instance of this organism has been discovered to date. So scientists have not been able to observe it further.[2]


The generic name, Parakaryon comes from Greek παρα (next to) and karyon (kernel, nucleus) and reflects its position between eu- and prokaryotes. The specific name, myojinensis reflects the locality where the samples have been collected: the hydrothermal vents at the Myōjin Knoll (明神海丘,[3] 32°06.2′N, 139°52.1′E) off the coast of Japan at a depth of 1240 m.[1]


  1. ^ a b Yamaguchi M, Mori Y, Kozuka Y, Okada H, Uematsu K, Tame A, Furukawa H, Maruyama T, Worman CO, Yokoyama K (2012). "Prokaryote or eukaryote? A unique microorganism from the deep sea". J Electron Microsc (Tokyo). 61 (6): 423–431. doi:10.1093/jmicro/dfs062. 
  2. ^ Nick Lane (2015). "Epilogue: From the Deep". The Vital Question: Energy, Evolution, and the Origins of Complex Life. W.W.Norton and Company. pp. 281–290. ISBN 978-0-393-08881-6. 
  3. ^ Fumitoshi MURAKAMI, The Forming Mechanism of the Submarine Caldera on Myojin Knoll in the Northern Part of the Izu-Ogasawara (Bonin) Arc