Scientists from Salk Institute have found that roundworms go through a teenager stage. Adolescent worms differ in behavior from adults even though they appear to have the same neurons. These young worms are less predictable and not as efficient at finding food. This may allow for flexibility in a potentially changing environment. The findings were just published in the journal eNeuro.
Juveniles and adults tend to differ in behavior but most previous studies have focused on mammals. Interestingly, scientists have observed differences in behavior between mature and adolescent Caenorhabditis elegans worms. C. elegans is a common scientific model used in research because they are small, transparent, and have simple genomes. Also called roundworms, they are some of the simplest organisms that still have true nervous systems.
Researchers noticed that adolescent C. elegans worms behaved a bit more erratically than adults. Adolescent worms were also much less efficient at finding food. Interestingly, adults and adolescent roundworms share the same exact neurons. To better observe what was happening, the team placed worms in the middle of shallow dishes. The researchers then placed a drop of diacetyl, a chemical that smells like buttery popcorn, on one side of the dish. C. elegans worms would normally show a strong preference for diacetyl as a food source but the adults were much quicker to respond to the smell. The juvenile worms were still interested in the chemical but took different paths or moved slower. When the researchers added a repellent instead, both adults and adolescents showed the same escape behaviors. This shows that the juveniles had full use of their sensory neurons but were more flexible in behaviors—they knew to escape from dangerous chemicals but had yet to develop a strong preference for a single food source.
Further analysis revealed that the adolescent worms were using different neuron pairs than the adults. Adults used more neurons when finding food and switching these neurons off made them exhibit juvenile behavior. In other words, adolescent worms don’t use all of their neurons until they reach adulthood. This would potentially give them an evolutionary advantage since they could adapt their behaviors based on their home environment.
The team’s findings show that even the simplest of organisms go through a “teenager” stage where they behave differently from adults—even though they technically have the same sensory neurons. This allows them to adapt to an environment that may differ from the home of their parents.
Hale et al. Altered Sensory Code Drives Juvenile-to-Adult Behavioral Maturation in Caenorhabditis elegans. eNeuro (2017).