Corals have been observed passing on mutations outside the reproductive cells, shattering more than a century of thinking about how evolution takes place.
Before Darwin, there was Lamarck, who postulated that qualities established during a person’s lifespan might be passed on to their progeny. Despite its intuitive attractiveness, the theory failed countless studies and has been generally dismissed since the late 1800s. However, something approximating Lamarckian inheritance has now been documented in corals, and it is possible that it is not unique to corals.
Lamarck imagined a society in which someone who exercised their muscles or brain may pass on more capacity to their progeny in those areas. A article published in Science Advances describes a separate but related ability in corals: the transmission of random mutations that would otherwise be lost. This is still considerably closer to Lamarckism than most scientists predicted.
“For a trait, such as growth rate, to evolve, the genetic basis of that feature must be transmitted down from generation to generation,” said Penn State University Professor Iliana Baums in a statement. “A novel genetic mutation can only contribute to evolutionary change in most species if it arises in a germline or reproductive cell, such as an egg or sperm cell. Mutations throughout the rest of the body, in somatic cells, were assumed to be evolutionarily inconsequential because they are not handed down to offspring. Corals, on the other hand, appear to have a way past this barrier, allowing them to breach this evolutionary law.”
Although genetic mutations are prevalent, evolution is typically sluggish. This is due in part to the fact that most mutations are detrimental or neutral, and even those that are helpful are seldom passed on to following generations.
“Reproductive cells are isolated from body cells early in development in most animals,” said graduate student Kate Vasquez Kuntz. Mutations in reproductive cells are passed on, but not those in the rest of the organism.
Corals can reproduce asexually by budding, which allows mutations to be passed on. They do, however, reproduce sexually, as evidenced by the amazing mass spawning events on the Great Barrier Reef.
Individual coral colonies generate both sperm and eggs, but having eggs from one colony fertilized by sperm from another colony increases genetic diversity and protects against parasites, therefore this is the usual.
Elkhorn coral, on the other hand, fertilizes itself on occasion. This significantly limits the number of possible genetic outcomes in offspring, making it easier for researchers to hunt for evidence of mutation transmission from non-reproductive (somatic) cells.
According to the study, corals produced by single-parent sexual reproduction inherited 50% of the somatic mutations in a large Elkhorn colony.
If it is the only time it occurs, the ramifications may be minor; nevertheless, the authors present preliminary evidence that it also occurs in colonies with two parents, which they want to confirm.
The scientists admit they don’t know how mutations go from somatic to reproductive cells, but they believe the distinction is insufficient.
Because so many somatic mutations are detrimental, passing them on would be disastrous for most creatures. However, Baums believes the strategy may work for corals due to characteristics that most other multi-celled lifeforms lack. “Because corals grow in colonies of genetically identical polyps, somatic mutations that occur in one coral polyp can be exposed to the environment and screened for utility without necessarily impacting the entire colony,” she explained.
Furthermore, the ability to pass on mutations might allow corals to adjust to environmental changes faster, which is wonderful news given the risks they currently face.
Evidence for Lamarckian evolution has been found in relatively simple organisms on occasion, although it is not universally accepted. Proponents credit this to repulsion toward Trofim Lysenko, who under Stalin established Lamarckism as dogma in the Soviet Union, with disastrous effects for both dissenting scientists and agricultural production.
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