Cellular and subcellular structure of neoproterozoic animal embryos.
Stereoblastic embryos from the Doushantuo Formation of China exhibit occasional asynchronous cell division, with diminishing blastomere volume as cleavage proceeded. Asynchronous cell division is common in modern embryos, implying that sophisticated mechanisms for differential cell division timing and embryonic cell lineage differentiation evolved before 551 million years ago. Subcellular structures akin to organelles, coated yolk granules, or lipid vesicles occur in these embryos. Paired reniform structures within embryo cells may represent fossil evidence of cells about to undergo division. Embryos exhibit no evidence of epithelial organization, even in embryos composed of approximately 1000 cells. Many of these features are compatible with metazoans, but the absence of epithelialization is consistent only with a stem-metazoan affinity for Doushantuo embryos.
Hagadorn
James W
JW
Department of Geology, Amherst College, Amherst, MA 01002, USA. jwhagadorn@amherst.edu
Xiao
Shuhai
S
Donoghue
Philip C J
PC
Bengtson
Stefan
S
Gostling
Neil J
NJ
Pawlowska
Maria
M
Raff
Elizabeth C
EC
Raff
Rudolf A
RA
Turner
F Rudolf
FR
Chongyu
Yin
Y
Zhou
Chuanming
C
Yuan
Xunlai
X
McFeely
Matthew B
MB
Stampanoni
Marco
M
Nealson
Kenneth H
KH
D000818:Animals; D001757:Blastomeres / Q000166:cytology; D002455:Cell Division; D019070:Cell Lineage; D048430:Cell Shape; D002681:China; D004625:Embryo, Nonmammalian / Q000166:cytology* / Q000648:ultrastructure; D047108:Embryonic Development; D004848:Epithelium / Q000196:embryology; D005580:Fossils; D005775:Gastrula / Q000166:cytology / Q000648:ultrastructure; D007448:Invertebrates / Q000196:embryology*; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D015388:Organelles / Q000648:ultrastructure; D014057:Tomography, X-Ray Computed