Research by the Queensland University of Technology has revealed that when it’s time to migrate, the free-living mushroom coral Cycloseris cyclolites defies traditional wisdom by heading directly towards the light. This study, spearheaded by Dr. Brett Lewis from the QUT School of Atmospheric and Earth Sciences and the Reef Restoration and Adaptation Program, was published in PLOS One and explored how this coral species moves, navigates, and reacts to light in its natural habitat.
“Not all corals are attached to the substrate; some are solitary and free-living, allowing them to migrate into preferred habitats,” Dr. Lewis said. “However, the lifestyle of these mobile corals, including how they move and navigate for migration, remains largely obscure.”
Cycloseris cyclolites is a species of mushroom coral that can move between various reef habitats, often in search of the best light conditions. Through high-resolution time-lapse imaging, researchers discovered that the species employs a technique called pulsed inflation. This involves the coral rhythmically inflating and deflating its tissue to push itself forward, similar to how jellyfish move. This method seems to be a common strategy among free-living corals, assisting in important functions like righting itself when flipped over, expelling sediment when buried during storms, and now, phototaxis—behaviours that enhance the coral’s chances of thriving in intricate environments.
“Our findings suggest that pulsed inflation is not just a survival strategy but a critical mechanism for migration and navigation,” Dr. Lewis said. “The ability of Cycloseris cyclolites to move towards specific light sources is a fascinating parallel to other marine species like jellyfish, which suggests they are more neurologically sophisticated than previously thought.”
Cycloseris cyclolites also demonstrated a notable inclination towards blue light, with 86.7% of the corals gravitating towards blue light sources, in contrast to only 20% for white light. This ability of migratory mushroom corals to differentiate between various light wavelengths corresponds with their preference for deeper water environments, where blue light is more prevalent. This capability may play a vital role in their movement to the most suitable depths for survival, reproduction, and dispersal.
The findings offer fresh perspectives on the mechanisms behind coral mobility, highlighting the similarities between these corals and jellyfish, which have been studied as a significant factor in the evolution of the centralised nervous system found in humans today.
“The findings also have important ecological implications,” Dr. Lewis said. “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. With these climate-driven factors increasing, the faster the migration, the higher the chance of survival.”