Balanophyllia europaea is a species of non-colonial hard coral, which is part of one of the 43 genera (Balanophyllia) that make up the family Dendrophylliidae in which there are a total of 550 described species. It lives exclusively in the Mediterranean, where it is found only on hard substrates and in well-lit regions, which limits its bathymetric range to 50 m depth.
Specimens of Balanophyllia europaea can grow their calcareous exoskeleton up to 6 cm in diameter and up to 2 cm in height, adopting an oval shape. The shape of their skeletons resembles the shape of a molar, with a central groove from which radial indentations emerge. The polyp has transparent tentacles, with some yellow, brown and red spots along its tentacles. This coloration is due to the presence of symbiotic algae within its tissue, which allows it to photosynthesize and therefore the need to be in well-lit environments. In the central groove we find the mouth cavity, which is elongated and oval in shape.
The food of this species is obtained predominantly from the symbiont algae inside its tissues. However, it complements its diet with the capture of zooplankton prey which it will catch during the night hours thanks to its tentacles.
It is a simultaneous hermaphrodite species, which means that the same specimen has both male and female reproductive organs. They reproduce once a year from May to April, when the eggs are fertilized and the larvae are formed. The larvae remain inside the specimen until they are released during September and October. The larvae will become part of the zooplankton for about a week, at which time the currents will disperse the larvae over a vast territory. After this time, the larvae will settle on the rocky bottom to undergo the process of metamorphosis and give rise to a polyp that will begin to grow into an adult specimen. Asexual reproduction is also possible through gemmation, a process that generates two completely identical specimens located at a short distance from each other.
It is possible to confuse this species with Balanophyllia regia, although the latter is smaller, has 48 tentacles and a golden yellow color.Photos: