While researchers have long understood the critical role insects play in the pollination of flowering plants, algae fertilization by marine animals was relatively unknown — and considered nonexistent. However, that conclusion is being re-evaluated after a team of researchers at the Roscoff Marine Station found that idoteas contribute to the red algae’s reproductive cycle. Gracilaria gracilis. This observation runs counter to previous research showing that the distribution of male algal gametes, or spermatia, depends on water movement rather than animal involvement. The scientists’ findings are published in the July 29 issue of Science and suggest that animal-mediated fertilization is much older than once thought.
The international research team led by Myriam Valero, a CNRS scientist associated with the research unit Evolutionary Biology and Ecology of Algae (CNRS/Pontificia Universidad Católica de Chile/Sorbonne University/Universidad Austral de Chile) and Roscoff Marine Station (CNRS/Sorbonne University) , has revealed that idoteas act as “sea bees” for Gracilaria gracilis – a seaweed that is used in IMTA projects and further processed into agar and carragheen.
Idoteas contribute to the fertilization of G. gracilis as they swim among these algae. The surfaces of the male algae are dotted with reproductive structures that produce spermatia that are covered in mucus, a sticky substance. When an idotea passes by, the spermatia attach to the cuticle and are then deposited on the thalli of any female alga the crustacean comes in contact with, helping G. gracilis reproduction.
But idoteas also benefit from this arrangement. The seaweed gives them space and costs: idotea clings to the algae to protect against strong currents, and they nibble on small organisms growing on their thalli. This is an example of a mutualistic interaction – a win-win situation for both plant and animal – and it is the first time animal-mediated fertilization of a seaweed has been observed.
While these initial findings do not indicate the extent to which animal transport of gametes contributes to algal fertilization relative to the role of water movement, they do provide surprising insight into the origin of animal-mediated plant fertilization.
Before this discovery, the latter was believed to have originated among terrestrial plants 140 million years ago. Red algae originated more than 800 million years ago, and their fertilization through animal intermediaries may predate the origin of land-based pollination.
Valero’s team now wants to focus on several other questions: Do idoteas trigger the release of spermatia? Are they able to distinguish males? G. gracilis algae from female individuals? And more importantly, are there similar interactions between other marine species?
Read more about the team’s research here.