Paramuricea clavata - Red gorgonian - Reproduction
In this dive of August 15, 2023 we filmed an event that has not yet been documented much in our Mediterranean Sea. This is the reproduction of the red Gorgonian (Paramuricea clavata). Like every year in summer, this beautiful coral reproduces with the synchronized emission of male and female gametes released by the polyps which open by extruding thin semi-transparent filaments exceptionally long up to 5 cm.
Timing and synchronization are important since the emission lasts only a short period of time and takes place, for what we have documented so far, in a precise period of the summer that is towards the end of August. Therefore it is very important that these colonies are synchronized to maximize the possibility of reproduction.
We are on a colony of Paramuricea clavata “quite young” since the branches of these gorgonians can reach even 1.5 – 2 meters in height and hundreds of years of age. The bottom of the colony varies from 49 to 53-54 meters deep and is about 7-7.5 miles from the coast. As can be seen, visibility in the water on the seabed is poor, also due to the many suspended organic particles carried by the current, which is always present and constant in the areas where the Paramuricea clavata lives.
Each colony consists of males and females. Sperm is released into the sea from the male colonies and fertilization occurs on the surface of the female colonies. The embryos are hatched there before being released as planula larvae into the water column. The larvae are photophobic and soon sink to the seabed. Once there, they develop into polyps and begin secreting gorgonine to form the skeleton. The further growth of the colony occurs through the “sprouting” of new polyps. Some new colonies may be formed from fragments that break away from existing colonies. Paramuricea clavata is a slow growing species and colonies live for over 50 years.
We recall that the IUCN Red List classifies Paramuricea clavata as a vulnerable species. In the past, red gorgonian colonies were very numerous, today we are witnessing their decline throughout the Mediterranean, especially in surface waters as a result of water heating. Other factors that threaten its survival are the indiscriminate collection by divers, and the damage inflicted by trawling. It is a very fragile and very slow growing species. By virtue of these characteristics it is considered a biological indicator of the balance of the marine ecosystem.