Thought Corals Were Stationary? Think Again – They’re Inflating And On The Move

Corals might appear stationary, but different species are capable of moving more than just their branches. In a new study, the mushroom coral Cycloseris cyclolites has been recorded navigating toward light, suggesting they’ve been underestimated until now. 

“Not all corals are attached to the substrate; some are solitary and free-living, allowing them to migrate into preferred habitats,” the study’s first author Dr Brett Lewis said in a statement. “However, the lifestyle of these mobile corals, including how they move and navigate for migration, remains largely obscure.”

C. cyclolites corals are typically small, with the largest measuring 9 centimeters (3.5 inches). The younger corals are typically known to start their lives attached to harder substrates but tend to move down into deeper water as they age. Free-living mushroom corals are thought to either be moved by the motion of the waves, hitchhiking on other moving animals, or actively moving through a process of inflating and deflating parts of their body.

The researchers were also interested in the response of corals to different light stimuli. In the deeper ocean, blue light wavelengths are more prevalent, so the team wanted to compare the movement of the corals in response to blue and white light to see which, if either, they favored. 

The researchers created aquariums covered in blackout housing so they could accurately access the response of the coral to a single light source. The team set up time-lapse cameras to record which directions the coral moved over 24 hours. The experiment consisted of 16 trials: six with white light, seven with blue light, and three trials where both blue and white light were presented. The distance traveled by the coral was recorded by measuring where the coral’s mouth was at the start and end of the experiment. 

During the experiments, 86.7 percent of the corals were found to move toward blue light, while only 13.3 percent of the corals moved toward white light. The corals did not move continuously, but rather via a period of pulses followed by a period of rest. During the trial with blue and white light combined, all the corals moved towards the blue light and away from the white light. 

The tissues at the bottom of the corals inflated, creating lift. They also increased their surface area further by using their ventral foot, and manipulated their tissues using contraction and twisting motion to propel themselves. This creates what the team calls “coordinated pulsed inflation locomotion”, similar to a jumping motion. After the jumps, the corals deflated back to their typical size. The team also noted that the inflated coral is also passively moved by the water flow, though not in the direction of the lights.

This new information about how these corals move and their preference for blue light could help scientists working to restore coral reefs damaged by bleaching and climate change. 

“Understanding their movement strategies could help scientists predict how migratory corals might resist, survive or adapt to changes in environmental conditions such as sea surface changes caused by climate change, which can be reduced by the deeper waters these corals migrate to,” explained Dr Lewis. “With these climate-driven factors increasing, the faster the migration, the higher the chance of survival.”

The paper is published in the journal PLOS One.

Source Link: Thought Corals Were Stationary? Think Again – They’re Inflating And On The Move