Helping with the germination of algae, crustaceans called idotea are the bee’s knees of the seas

Flowering plants are one of Earth’s most beautiful treasures – but what about plants under water?

Flowering plants, or angiosperms, formed during the Cretaceous period around 100-125 million years ago. And, as they evolved, along with them came the equally vibrant and wonderful pollinators like bees and butterflies.

In fact, animal-mediated fertilisation of plants on land is thought to have developed even earlier, around 140 million years ago. Bees don’t live underwater but crustaceans do.

New research published in Science suggests these sea animals are involved in the reproductive cycle of algae much like pollinating insects on land.

Male gametes, or spermatia, of red algae predominantly rely on water movement to spread and fertilise. Until now, scientists hadn’t recognised the role played by animals in this process.

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An international team of researchers from the French National Center for Scientific Research (CNRS), University of Paris, the Austral University of Chile, and the Pontifical Catholic University of Chile believe that tiny marine crustaceans called idoteas act as ‘sea bees’ for the red alga Gracilaria gracilis.

Swimming through microscopic algae forests, the idoteas inadvertently pick up G. gracilis spermatia which are coated with a mucus-like, sticky substance. The critters then deposit the spermatia on the thalli of female algae they come across, aiding in G. gracilis reproduction.

It’s not very intimate, but it gets the job done.

On land, bees don’t just pollinate for the sake of it, or to be nice to the flowers. They benefit a lot from their relationship with flowers, gaining the sweet nectar that they bear.

Similarly, the idoteas also have a mutually beneficial relationship with the algae which give them a safe home. Clinging to the algae, the crustaceans are protected from strong currents. They also gobble up the even smaller organisms that cling to the algae thalli.

It is the first time such a win-win interaction between seaweed and an animal has been observed.

Still unclear is just how much such animal-mediated transport of gametes actually contributes to the reproduction cycle of the algae. However, given red algae evolved over 800 million years ago, they have had around six times as long as flowering plants to develop such relationships with animals.

The team now hopes to answer further questions like whether or not the idotea trigger the release of spermatia, if the crustaceans can distinguish between male and female G. gracilis, and if there are other examples of animal-mediated reproduction in other marine species.