In DepthEvolution

Did neurons arise from an early secretory cell?

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Science  18 Jan 2019:
Vol. 363, Issue 6424, pp. 212-213
DOI: 10.1126/science.363.6424.212

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Summary

Swimming through the oceans, voraciously consuming plankton and other small creatures—and occasionally startling a swimmer—the beautiful gelatinous masses known as comb jellies won't be joining Mensa anytime soon. But these fragile creatures have nerve cells—and they offer insights about the evolutionary origins of all nervous systems, including our own. Inspired by their studies of a glue-secreting cell unique to these plankton predators, researchers have now proposed that in the last common ancestor to today's animals, the earliest neurons arose from secretory cells whose primary function was to release chemicals into the environment. The researchers also unearthed additional evidence in jellyfish, hydra, and fruit flies that neurons and other secretory cell types come from the same progenitor cells in embryos. The work could help resolve a long debate about whether the nervous system evolved twice early in animal life.