Through the lens of time-lapse photography: uncovering hidden behaviours in the mesophotic coral Dendrophyllia ramea and other natural history observations

Time-lapse photography provides unprecedented insights into marine organism behaviours that are otherwise difficult to detect through direct observations. We monitored a colony of the habitat-forming coral Dendrophyllia ramea at 70 m depth in the upper mesophotic zone for six consecutive days. Our observations aimed to describe the colony’s polyp activity patterns, investigating diel periodicity and feeding preferences. We additionally documented interactions with associated marine fauna, including the homing behaviour of the sea urchin Centrostephanus longispinus and the composition of the local fish community. Results revealed that the natural state of D. ramea polyps is to have tentacles extended. However, by analysing polyp closure, distinct temporal patterns emerged, strongly influenced by tidal fluctuations. The description of interspecific relationships highlights the essential role of D. ramea in benthic ecosystems, particularly regarding the provision of shelters for benthic fauna and the attraction of several fish species, thus providing information for conservation strategies for vulnerable mesophotic habitats.