Kelp: some seaweeds reproduce without a partner
· BehindLines newsroom
When partners are scarce, a species of kelp can do without fertilisation. This is what a study that appeared in PLoS Biology on 12 November describes, and Nature magazine has also covered it. It concerns Laminaria pallida, a brown alga from the Atlantic shores of southern Africa.
What the team observed
According to Nature, microscopic male and female organisms, grown separately in laboratory dishes, were able to produce offspring without fertilisation. This had already been documented for one male strain, according to the magazine; the study shows it was not an isolated case. In males, gene activity changes during this asexual reproduction and moves closer to that of females. The authors combined gene-expression analyses, developmental experiments and sampling of natural populations.
An option kept for situations without a partner
Under the same laboratory conditions, the presence of an individual of the opposite sex tips the balance towards sexual reproduction, which suggests, according to Nature, that the algae detect a nearby partner. The authors, in PLoS Biology, link the asexual route to endoreduplication and to lower fitness of the offspring, with delayed development. In the wild, the PLoS Biology abstract says it persists but seldom shows up in two populations; among 523 individuals sampled, Nature reports no clear sign of this mode of reproduction.
Specialists react
Daniel Liesner, of GEOMAR, first author, considers kelp more flexible than previously thought. Reina Veenhof, of the Scottish Association for Marine Science, finds the study interesting because it sheds light on how gene activity allows these modes of reproduction. Olivier De Clerck, a seaweed biologist, finds it striking that male cells can develop alone, since they are small and have few reserves.
Why it matters
Kelp provide food and shelter for many marine animals, Nature recalls. The authors of the study propose that asexual reproduction serves as a fallback when partners become scarce, while keeping the long-term benefits of sex when they are present. This conclusion rests on a single species, observed partly in the laboratory; it does not say that other algae behave the same way.