Genetic Markers Reveal Secret Sex Life of Ocean Diatoms

Diatoms, a vital group of marine phytoplankton, have long presented a puzzle. Their cellular division causes them to progressively shrink, and the only way to reverse this is through sexual reproduction. Yet, directly observing this behaviour in the vastness of the ocean is incredibly difficult, leading many to assume it was an infrequent occurrence.

To solve this mystery, researchers developed a novel method. By studying four diatom species in controlled lab experiments, they identified a set of conserved 'marker genes' that are switched on only during sex. This genetic toolkit acts as a reliable signal for detecting reproductive events in the wild, even when the diatoms themselves cannot be seen in the act.

Applying this tool to global data from the Tara Oceans expedition, the team found widespread expression of these markers across the seas. The analysis revealed coordinated sexual activity in nine different diatom genera, including both dominant bloom-forming species and rarer types. The discovery confirms that diatom sex is far more widespread than previously thought, a pivotal process for their evolutionary success.