Split-fan kelp switch between sexual and asexual reproduction depending on whether potential mates are nearby, according to a study published in PLOS Biology on Thursday.
Although most animals reproduce sexually, asexual reproduction remains common in plants, fungi, and algae. Researchers still poorly understand how and why organisms choose between these reproductive strategies. To investigate this puzzle, scientists studied laboratory and wild populations of the split-fan kelp (Laminaria pallida), a large brown seaweed species found along the Southern Atlantic coast.
Laboratory experiments revealed that both male and female specimens are capable of reproducing asexually. However, asexual reproduction produced fewer offspring, which tended to exhibit developmental abnormalities and slower growth, as Science X reported.
To understand the molecular mechanisms underpinning kelp reproduction, researchers sequenced RNA from male and female kelp at different stages of sexual and asexual reproduction. While the gene expression profiles of male and female kelp were initially unique, male gene expression shifted during asexual reproduction, losing its masculine characteristics and aligning more closely with female patterns.
Upon gathering 523 wild split-fan kelp specimens across Namibia and South Africa, the team discovered that asexual reproduction does not occur in natural settings. However, when wild kelp were grown in single-sex cultures in the lab, 92% reproduced asexually.
The team proposed that the proximity of the opposite sex could potentially inhibit asexual reproduction, which would account for why this behavior appeared in laboratory settings but remained absent in the wild.
To test this hypothesis, scientists grew male and female kelp in the same Petri dish, separated by a fine mesh. Both sexes were significantly more likely to reproduce asexually in the absence of a suitable mating partner.
This suggests a chemical signal in water may suppress asexual reproduction and alert kelp to nearby mates. This research highlights a surprising degree of adaptability within the kelp life cycle, shedding light on the mechanisms used to navigate between various reproductive modes.
Even though asexual reproduction is not as efficient, it could serve as a secondary option for kelp living in low-density environments or facing environmental hardship. These findings may help conservationists protect this ecologically important marine species in a changing ocean environment.
