Death begins with an organised and consistent pattern of change. This is the conclusion drawn by a study that observed a simple worm (C. elegans) dying. When UV light was shone upon it, they found that as it began to die, the intensity of blue light emitted from it grew travelling from one end of the intestine to the other, and it reached its maximum density at the moment it died, before fading away.
This blue light is created because of fluorescence of simple molecules called anthranilic acids. These are generated when cell walls break open releasing them. Because the intensity slowly increased, it meant that cells were dying sequentially before the death of an organism occurred.
This is counterintuitive to theory which has persisted about death. That theory states death occurs because damage accumulates in cells. If that were the case then all cells in the worm should’ve glowed simultaneously and the intensity ought to have increased in all of them, which was not observed.
Reference: C Coburn et al. PLOS Biology 2013
Further reading: Luc Henry in The Conversation
Image credit: Wellcome Trust