“Our findings highlight that kelp are even more flexible in their reproduction than previously appreciated,” said Daniel Liesner, a marine biologist at the GEOMAR Helmholtz Centre for Ocean Research Kiel in Germany.
When potential mates are scarce, some seaweeds can switch to asexual reproduction. This was published on November 12 in PLOS Biology. The brown algae provide food and shelter for marine life.
“Kelps are really weird, they do all kinds of stuff,” said Reina Veenhof, an ecologist at the Scottish Association for Marine Science in Oban, UK. She said the research is intriguing because it sheds light on the mechanisms of gene activity shifts enabling diverse reproductive strategies in kelp.
Scientists already knew that unfertilized kelp eggs could develop into offspring. This process was documented for one male strain, and the PLOS Biology study shows that this was not a one-off.
Researchers focused on Laminaria pallida, a species found along the Atlantic coasts of South Africa and Namibia. Microscopic male and female kelp grown in separate laboratory dishes produced offspring without fertilization. This mechanism might provide a way to keep reproduction going when finding a mate is impossible. Many organisms move between different life stages and can reproduce either sexually or asexually.
“Finding that males can reproduce asexually was completely unexpected,” said Daniel Liesner, lead researcher on the project.
Reproducing independently results in weaker descendants. It can still provide a benefit when partners are difficult to find.
In the absence of potential mates, asexual reproduction increases.
During asexual reproduction, the gene expression in males changed. This change made them more similar to females.
Kelp preferred sexual reproduction when cultivated in a laboratory setting alongside a member of the opposite sex. This points to their ability to sense adjacent partners via chemical cues. Experimental trials demonstrated that the physical presence of potential mating partners actively suppresses asexual development.
This indicates that reproductive mode is adjusted in response to reproductive opportunities. Keeping sexual pathways intact enables the kelp to reap the enduring advantages of sex whenever partners become available.
To examine whether asexual reproduction occurs naturally, the authors paired the experiments with field samples from South Africa and Namibia. Among 523 individual wild sporophytes examined, they found no clear evidence of asexual reproduction or unambiguous genetic signatures of clonality in the wild.
That lack of findings does not rule out the possibility that the phenomenon happens. It indicates that the researchers found no signs of it within that particular group.
Labeling this behavior as a confirmed survival tactic in wild kelp environments would be hasty. Laboratory potential does not guarantee that the mechanism happens frequently outside of a controlled setting, and “we don’t know whether this is ecologically relevant,” as Liesner said.