When potential mates are scarce, some types of seaweed can take reproduction into their own hands, so to speak, according to a study published on 12 November in PLoS Biology¹.

“Our findings highlight that kelp are even more flexible in their reproduction than previously appreciated,” says Daniel Liesner, a marine biologist at the GEOMAR Helmholtz Centre for Ocean Research Kiel in Germany.

The brown algae, which provide food and shelter for marine life, “are really weird, they do all kinds of stuff”, says Reina Veenhof, an ecologist at the Scottish Association for Marine Science in Oban, UK. What’s interesting about the study is that it helps to explain how changes in gene activity allow kelp to reproduce in different ways, she says.

Developmental flexibility

Scientists know that kelp can reproduce asexually, with unfertilized eggs developing into offspring. This process was even documented for one male strain² — the PLoS Biology study shows that this wasn’t a one-off.

The ability of male reproductive cells to develop without fertilization is striking, says Olivier De Clerck, a seaweed biologist at Ghent University in Belgium. This is because, unlike eggs, sperm cells are small and have few resources to support development.

The researchers focused on Laminaria pallida, a species found along the Atlantic coasts of South Africa and Namibia. In the wild, 523 individual kelp showed no clear evidence of asexual reproduction.

By contrast, both microscopic male and female L. pallida grown in separate laboratory dishes could produce offspring without fertilization. During asexual reproduction, the gene expression in males changed, making them more similar to females.

However, when they were lab-grown in the presence of a member of the opposite sex, kelp favoured sexual reproduction, suggesting they can detect nearby partners through chemical signals.