Several researchers claim to have found a death wave. It's the edge of death as it kills an animal. Well, worms:
The death wave (a.k.a. "death fluorescence", or DF) starts in the worms' intestines and spreads via "a stereotyped process of self-destruction involving an intra- and intercellular cascade of cellular necrosis"
See it start around 2:54 here:
"It's like a blue grim reaper, tracking death as it spreads throughout the organism until all life is extinguished," study co-author Prof. David Gems, professor of biogerontology at University College London's Healthy Ageing Institute, said in a written statement issued by the university.
(thanks to J. Wolfe)