Sexuality is not only in humans, but also in nature often more and more complex than just being together and the exchange of two partners. That has been known for a long time. Apparently, however, as a team of experts in marine biology has now found out, the sexual intercourse with three participants is even much older than previously assumed.
But that finding gave the Chilean marine biologist Myriam Valero no peace. The director at the research station in Roscoff in France wondered whether something similar could not also happen with the evolutionarily much older organisms, for which she herself is an expert: The red algae species Gracilaria gracilis, which is distributed worldwide, can spread asexually, for example via spores, but also propagate historically. The latter, as has been assumed so far, happens passively, in that the male sex cells, called spermatia, detach from the algae and get stuck on the female organ, called Karpogon.
Red algae have been around for about 800 million years, and plant and animal life on land probably less than 500. So it’s possible that something comparable to the pollination of land plants by bees, moths, or hummingbirds existed long before the land beyond colonized by microorganisms at all, has developed in the sea.
For example, while bees are rewarded with pollen and nectar, it is still unclear what the sex workers of the red algae get for their service. A companion article in Science, where the research paper itself appeared, speculates that they are simply offered protection from predators there. Even effectively, they are likely to find food there as well, namely various types of unicellular algae that grow on top of the large red algae.
The question of how important this type of reproduction is for the red algae under natural conditions remains unanswered. The same applies to whether and which other groups of marine plants – or even animals – also use this option of “cross-pollination”.
In strongly moving water, the sex cells should actually be able to leave the father plant far enough to reach a Karpogon without animal help. On the other hand, many will then be washed out into the open water and, as it were, lost.
The effective transmission by Idotea and others could also have led to the algae having to produce fewer spermatozoa and thus being able to save energy. It would be a very similar evolutionary step from wind to land cross-pollination.
It is also currently unclear what practical significance the find may have. In any case, the red algae species is considered to be one of the most promising marine resources of the future because of its ingredients that can be used in specialty chemicals and medicine, among other things.
