British scientists have shown that early mortality of adults of the nematode Caenorhabditis elegans might be evolutionarily advantageous for a population. They modeled the development of colonies of worms in the conditions of limited resources and found that even if nematodes remain fertile until death, population is beneficial to adults died earlier, then enough food for developing larvae. This is especially important when Mature worms consume a lot of resources — those who eats a lot, die, to the descendants of not starving. Article published in the journal Aging Cell.
The question of what are the functions of aging and what evolutionary advantages it brings, is on the minds of scientists for a long time. According to one version, the aging clears the population from the “worn out” individuals to save resources for the young and promising. The modern theory of evolution does not support this hypothesis, at least for species that live in not very crowded. A high probability that altruistic death will make use of more selfish individuals, and in this case suicide will not be evolutionary advantageous.
However, species which live very closely and are actively competing for resources. If the genotype of different individuals differ slightly (this happens when organisms reproduce asexually or are hermaphroditic), then altruistic behavior can be beneficial to passing on genes to the next generation.
The nematode Caenorhabditis elegans — a well-known model organism on which to study processes of aging. They have already found a number of genes off which leads to a significant increase in life expectancy — mean, normally these worms have mechanisms that limit the length of life. However, the adaptive role of such processes is not clear until the end.
David gems (David Gems) and Evgeniy Galimov, from University College London suggested that hermaphroditic C. elegans, which live very close populations, altruistic death can be an adaptive mechanism. The researchers built a computer model in which the worms lived in the environment of 300 by 300 cells, with food in the center. The model was placed one larva and followed the development of the colony, which grew out of them.
The virtual life cycle of nematodes consisted of three stages: two larval and one adult. In the absence of eating one of the larvae moved into the sleeping phase and the other turned into dorovskoy the larvae, which are present in C. elegans , for settlement. Production dorovskih larvae and served as a measure of fitness of the colony — because it is through these individuals nematodes exploit new territories and create new colonies.
The researchers changed the life expectancy of the model C. elegans, their performance and its dependence on age. Unexpectedly, even if the fertility of the nematodes did not decrease with age, early mortality increased the fitness of the colony. The fact is that if the worms are long-lived, then the share of the food that you consume adults — to the detriment of the larvae. In this case, the resources quickly run out and no matter how many eggs lays nematodes for their long life, the don’t have enough food to turn into dorovskoy larva.
The benefit of early mortality for the colony was more if C. elegans lost fecundity with age — fed animals, which did not leave offspring, it is not profitable, or when the number of larvae produced by one nematode. In the latter case increases the number of individuals and competition for resources.
When the scientists increased the amount of food that adults eat worms, colonies were favorable to the genotype of early mortality. The authors explain that individuals who used many resources have to die early. In addition, the model confirmed the adaptability of declining consumer activity with age, which see a real C. elegans.
In nature there are amazing examples of sacrifice of individuals is evolutionary advantageous. For example, bacteria in the clone wars arrange a mass suicide. They are ruining their own shell and secrete toxic substances that kill opponents.