Hong, R.L. et al eLife 8, e47155 (2019)

100 million years ago, two nematodes diverged from their last common answer. Caenorhabditis elegans forged a free-living path, while its relative Pristionchus pacificus tends to keep the company of various scarab beetles. The worms look similar but behave differently. A new study compares the brains of the two worms to try and better understand why.

The multi-institution team focused on neurons in the amphid sensilla, a sensory organ. Some features were conserved, such as the number of neurons present and how those neurons were positioned. But at finer detail, differences emerged in morphological structures and the connections between neurons. The authors suggest there are evolutionary constraints on how neurons can be patterned in the brain, leaving dendritic structure and synaptic connectivity to diverge over time and contribute to those behavioral differences.