Researchers from the University of California at San Diego created an underwater microscope that allows a detailed view of wild corals in reefs. A video captured by the lens shows the polyps “kissing”.

Andrew Mullen and Tali Treibitz, investigators from the Scripps Institution of Oceanography at the University of California created the Benthic Underwater Microscope (BUM) to understand better how the coral polyps -which are less than a centimeter tall- interact with each other.

A new device that peers at corals in their natural habitat could help us understand how the world’s reefs respond to climate change. Credit: National Geographic/MIT Technology Review

A study published Tuesday in Nature showed that the polys, a tiny animal very similar to anemones, move non-stop, “kissing” and “dancing” which each other. Scientists suspect that in this process, polyps are exchanging nutrients with each other, as they press their mouths together. The small species feed on algae, bacteria, and microbes their surfaces can reach.

Researchers set the microscope in a reef in the Red Sea to record the corals movements during the night and found out the next day that the small species are constantly leaning towards each other. This is an entirely new view of the corals that only the BUM has allowed.

“Normally when you study a coral reef it can be difficult to observe the corals as active animals because the individual polyps are so small, and they typically move slowly,” Mullen said in a statement. “With the underwater microscope, we can look at very small spatial scales and record activity over several hours.”

The new microscope has a membrane similar to the human eye

The lens of the invention of Mullen and Treibitz were built to work like the human eye, consisting of a flexible membrane that is surrounded by a fluid. The pressure applied to the fluid defines the shape of the membrane, controlling the depth of the focus. The lens was placed 6 centimeters apart from the corals to avoid disturbing them, Mullen told National Geographic.

The BUM captures high-resolution images from objects as small as 10 micrometers, which is about a tenth of the width of a human hair. Previews underwater microscopes reached a resolution between 20 and 50 micrometers. The new microscope can work to a maximum of 100 feet of water.

BUM includes a camera and 6 LEDs to work as a flash, so the microscope can still capture the high-resolution images in spite of darkness and distortion of the sea.

The videos captured show a new point of view, which investigating coral samples under a microscope in a lab did not allow.

The study also mentions that polyps are not just feeding on near algae. By using venomous cells, they hunt plankton and share it between them.

Mullen and Treibitz also experimented with the potential microscopic captures by moving a sample of a coral colony next to another of a different kind. The BUM caught the local polyps fighting the newly arrived ones by expelling a white web, called “mesenterial filaments,” according to the researchers. These filaments are part of the digestive system of the corals, and they kill the invaders by digesting them, because of the stinging cells that comprise them.

“We think they might use some kind of chemical sensing to be able to recognize that their neighbor is of the same species,” Mullen stated.

The BUM also registered details about the bleaching phenomenon that is attacking coral reefs around the world. Warm temperatures of the water cause corals to detach from the algae that feed them, making them weak and colorless. Then, another type of algae grows over the corals, or at least, it was believed so. The captures from the microscope showed that the algae grow between the polyps and not around them. This finding will let scientists understand better the conditions of the corals during the bleaching.

Source: National Geographic