Tiny Crustaceans Pollinate Red Algae Like a Bee of the Sea

Tiny crustaceans pollinate red algae like a sea bee

It is well known that insects like bees help plants reproduce by carrying pollen from one plant to another. However, recent research has revealed that red algae and tiny crustaceans form a similar arrangement in the sea.

As an essential food source for humans and marine life, crustaceans play an important role in the ecosystem. Larger crustaceans can serve as a food source for large aquatic mammals, while smaller crustaceans can recycle nutrients as filter feeders. A new study has found that crustaceans improve the reproductive rate of red algae by moving sperm from the male algae to the female algae.

The study

The study was led by population geneticist Myriam Valero of the Center National de la Recherche Scientifique (CNRS) and PhD student Emma Lavaut of the Sorbonne University in France. They worked partly from the Roscoff marine station at the Sorbonne, alongside their institutions and associates from the Austral University of Chile.

Tiny crustaceans pollinate red algae like a sea bee
In this photo of idotea, the legs of the animal are covered with spermatia of red (green) algae. (Credit: Sebastien Colin)

The researchers looked at a type of red algae called Gracilaria gracilis and marine isopods (tiny crustaceans) known as idoteas (specifically Idotea balthica).

Until recently, researchers thought that algae, not plants or animals, benefited from underwater currents that carried gametes (reproductive cells) from one type of algae to another. However, male algal gametes are unable to swim on their own because they lack sperm-like flagella.

Crustaceans Algae foraging

Scientists have learned through tests and field observations that idoteas play a supporting role. For example, it has been found that when crustaceans feed on the male algae G. gracilis, the spermatia or male gametes, which are produced by structures that dot the surface of the algae, attach to the animals’ cuticles in a sticky state and coated with mucilage.

Some spermatia are transported to the reproductive organ of the female alga when the same idoteas are deposited there, thus completing the fertilization process. Seaweed also benefits idoteas because it protects them from the environment and has microscopic creatures on their surface that they can consume.

Tiny crustaceans pollinate red algae like a sea bee
A diagram of the fertilization process shows how it also benefits idoteas. (Credit: Lavaut et al.)

Since underwater currents undoubtedly play an important role, it remains unclear what percentage of gamete distribution is provided by crustaceans. Nevertheless, research provides evidence that insect pollination of plants may have developed from a process that began in water. An article about the study was published on July 28, 2022 in Science.

Crustaceans at Risk

Unfortunately, crustaceans can be threatened by pollutants accumulated by humans. A previous study, published in Nature Ecology and Evolution, found crustaceans poisoned by pollution in the Mariana Trench.

The team examined various species of tiny foraging crustaceans called amphipods that were collected between 7,000 and 10,500 meters below the surface of the Mariana and Kermadec Trenches in the western Pacific. The researchers found that these animals were rich in two types of persistent organic pollutants (POPs), regardless of depth, species or trench.

Exposure to POPs can decrease reproductive success and hence population expansion of organisms found in shallower waters. Although it is difficult to study deeper animals living in a controlled environment, we can assume that contaminants have a similar impact. Although there are notable differences between the trenches and the types of pollutants, the key finding is that some of the most extreme and remote places on Earth have a significant human footprint.

These pollutants in the open ocean are particularly problematic because they are naturally hydrophobic or attracted to things other than water. This includes tiny flakes of larger corpses known as “sea snow” that descend through the ocean and provide most of the energy for the deep sea. As a result, the primary food supply mechanism at great depths also serves as a highly efficient means of dumping pollution.

Fortunately, POPs were banned by the Stockholm Convention of 2001 once people realized that these chemicals were a terrible contribution to the world. But apparently he can still hang out in the deep sea.

Tiny crustaceans pollinate red algae like a sea bee

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