By Reef Check Italia’s Gianfranco Rossi
Paramuricea clavata is an endemic gorgonian of the Mediterranean Sea. Its presence characterizes some of the very best dive sites. Its role is crucial for maintaining the integrity of one of the areas with the highest rate of biodiversity on the planet: the Mediterranean coralligenous. In this habitat, the wonderful fans of this gorgonian extend from the substrate with upright branches that form true underwater forests. The dark bluish color, due to the reduced brightness of the environment where they grow, creates scenarios that arouse deep admiration in any diver.
Unfortunately very little is known about the biology of Paramuricea clavata; not only by scuba divers but also by researchers to which many aspects of the life of these organisms are still poorly known.
As a result, the Gorgonians Campaign 2012 was launched by Reef Check Italia Onlus. Besides asking volunteers to record information on the distribution and abundance of these organisms, the importance of observations indicating any presence of tiny eggs laid on the branches’ surfaces has also been highlighted. Knowing the gorgonian distribution while obtaining information on the period they’re breeding could generate data of great scientific relevance. Paramuricea clavata belongs to the Octocorals; in this group two different kinds of reproduction are known: the first one consists of broadcast spawning with fertilization and development in the water column, while the second one occurs when fertilization and brooding take place on the adult colony.
Colonies of P. clavata have separate sexes, meaning that single individuals are female or male, and the presence of hermaphrodites is very rare. Sperm is released in the form of tiny white-yellowish color
ed spherules, while the eggs are a purple-bluish color. To be effective, female and male spawning must be synchronous.
The eggs remain aggregated by a thin layer of a mucous material adhered to the surface of the branches of the mother colony. After being fertilized, the eggs ripen through different stages until they produce a planula that detaches from the mother colony to colonize the surrounding territory. Once settled on the substrate, the planula ripens into a single polyp from which begins the asexual reproduction that will create a new colony.
The months of June and July are considered the ideal period for the reproduction of gorgonians, meaning that it is possible to observe this phenomenon. All you have to do is carefully examine the gorgonian’s surfaces, and with great care you could spot a myriad of tiny whitish or bluish eggs spread along the various branches. This is what has happened to many divers who have experienced a way of diving characterized by increased awareness of the extraordinary phenomena that often occurs under our eyes but inevitably passes unnoticed because of the lack of appropriate knowledge.
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