We used to think that underwater pollination was achieved through water flows, but new research has found that an isopod has been marching around under the sea fertilizing plants like a little bee (strap in because there’s plenty more rhyming where that came from). These Idoteas – the name given to the seas’ bees – adds to a small and recent body of research that demonstrates that animal-mediated pollination isn’t exclusive to terrestrial plants, as was previously thought.
“The long-held belief that animal-mediated pollination is absent in the sea has recently been contradicted in seagrasses, motivating investigations of other marine phyla,” write the authors of a new paper published today in Science. They recognized that red algae could be a good candidate for pollination since the male gametes aren’t able to get around by themselves.
Before now, it was thought that seagrass and seaweed were fertilized with the aid of water flows that could sweep up male gametes and redistribute them across plants’ female reproductive parts. Could it be that, instead, some kind of sea bee was fertilizing the algae (perhaps an Idotea)?
Yes. Yes it could.
A series of experiments involving red algae revealed that the isopod species Idotea balhica was common among red algae (Gracilaria gracilis), and that their presence significantly boosted fertilization. They were able to confirm the connection by zooming in on the isopods showing their bodies sometimes picked up the seaweed’s spermatia like pollen sticking to a bee, which the Idoteas could then deliver to the necessary reproductive parts by wandering over female plants.
It seems the isopod-seaweed duo may represent a mutualistic relationship, as while the algae benefits from the fertilization, the Idoteas also enjoy shelter and a rich buffet of diatoms.
As well as adding another invertebrate to the pollinator roster, the research has interesting implications for the evolution of animal-mediated fertilization. It seems the mode of fertilization has evolved independently in both terrestrial and marine environments, but whether it began in the sea before moving onto land remains to be seen.
“The study by Lavaut et al. has broadened both the variety and the history of animal-mediated male gamete transfer, taking the concept of pollination from plants to algae and potentially pushing it back to the earliest evolution of marine invertebrates,” write Jeff Ollerton and Zong-Xin Ren in a related perspective paper on whether pollination existed before plants.