Researchers have found that worms experience rigor mortis before, rather than after death as humans do. The study is the first to observe rigor mortis in worms and provides a little insight into the biological processes experienced by an organism when it dies. The international team of scientists from Washington University and UCL used the C. elegans roundworm to learn a bit more about death from old age, something that is not well understood. Their findings have been reported in Cell Reports.
"Cell death has been widely studied but much less is known about [the] death of whole organisms, how it happens, what triggers it, and when it begins and ends. But it's extremely important for understanding fatal diseases in humans, especially those caused by aging," said research leader Professor David Gems of the UCL Institute of Healthy Aging.
Death is defined by a lack of heart or brain function; when it ceases, an organism is considered dead. But there are many physiological events before and after death. In C. elegans, cell death spreads through the animal. As a cell dies, it triggers the death of neighboring cells by releasing calcium. The process starts with muscles, causing hypercontraction and rigor mortis.
"The way death spreads from cell to cell by calcium is like a house burning down," explained lead author Dr. Evgeniy Galimov, of the UCL Institute of Healthy Aging.
When a person dies, stiffness sets in. That rigor mortis in followed necrotic degeneration and muscles get soft again. That process is a consideration in the meat industry; the product has to be tender. It can also help forensic studies that seek to establish a time of death. C. elegans undergo a similar series of contraction and relaxation in their muscles as they die.
"What really surprised us at first was that rigor mortis in worms begins while they are still alive. But then we realized that death from circulatory failure, as in mammals, doesn't happen in C. elegans. The worms are so small they don't need a circulatory system to get oxygen for respiration," explained Dr. Galimov.
"Dying C. elegans also undergo what we term a 'belly punch' phenomenon where death contraction in the head drives the pharynx backward into the intestine, and the impact triggers cell death," noted Professor Gems.
This work, which you can learn more about from the video above, suggests that declines that are a hallmark of old age may be due to an inability to generate cellular fuel, ATP. That leads to a failure to contain calcium within the cell. When it is released, it causes cellular necrosis.
"Discovering rigor mortis in worms is exciting as it highlights a key step in the chain of events leading from healthy adulthood to death from old age. It helps us to understand death in humans, and perhaps in the future to prevent death in mortally ill patients," concluded Professor Gems.