Marine scientists have shared a surprisingly endearing video of an eastern oyster larva feeding on algae.
The video is important for more than just its cute value. It has helped scientists highlight the importance of gravity in the feeding process of these tiny creatures – which, it turns out, may present issues for oysters in the future.
Eastern oyster larvae are miniscule. An individual usually measures between 100 and 300 micrometres long (that’s 0.1 to 0.3mm). For context, an individual grain of sea salt is typically between 0.22mm and 0.93mm.
Because these animals are so small, the scientists had to develop a special imaging technique to film the feeding larvae without disturbing them. In the footage – which has been slowed down by ten times – an adorable little oyster larva drifts through the water, fluttering its hair-like cilia to capture floating particles of algae.
Researchers long thought that these larvae created currents to draw food towards them using the drag from their swimming movement.
By tracking the tiny particles in the water, the video shows that they actually bring food towards their hungry little mouths using gravity. The larva’s shell is heavier than the seawater around it and so produces a current that brings the food straight to it, like an ocean-based meal delivery service. The findings are published in Physical Review Fluids.
“Thanks to high-speed imaging, we now see that gravity is essential for their feeding,” says the study’s author Houshuo Jiang, a senior scientist at the Woods Hole Oceanographic Institution (WHOI).
“This tells us that the shell is doing more than just protecting the animal,” says Jiang. “It is actually helping the larva feed. That means anything that changes the shell could also change how the larva gets its food.”
This is concerning because the ocean is becoming increasingly acidic. Ocean acidification makes it harder for animals with hard calcium carbonate exteriors – such as oysters, mussels and corals – to create and maintain their structures.
If an oyster larva was unable to create as strong a shell, it might become less dense and struggle to feed using these gravity-driven currents.
“Ultimately, this could help us better understand what determines whether oyster larvae survive and become part of the adult population,” says Jiang. “If environmental stressors affect both shell formation and feeding, we need to understand those effects to better predict how oyster populations will respond to a changing ocean.”
Find out more about the study, published in Physical Review Fluids.
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Top image: Houshuo Jiang, Woods Hole Oceanographic Institution
