Gold coral

(Savalia savaglia)

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    S. savaglia

The gold coral (Savalia savaglia) is a mysteriously charming animal that lives attached to the bottom (i.e., it is benthonic). I say “mysterious” because, as it normally lives rather deep (from at least 40 m) and alone like a tree on a beach, it is extremely coveted by recreational scuba divers in the Mediterranean. Personally I grew up with the myth of the gold coral – and my heart still beats so fast when I spot it…

First thing first, though. Savalia savaglia has a lot to share with the gorgonians. Like these it belongs to the class of the so-called flower-animals (Anthozoa), that is, it is a colonial organism made of polyps. Which, when open, are in charge of filtering the sea water to provide nutrients to the colony.

Yet the gorgonian polyps have 8 tentacles (whence the sub-class name, Octocorallia), whereas here they’re a multiple of 6 (whence the sub-class name, Hexacorallia) generally organized in two crowns of 12. From this point of view, then, the gold coral’s nearest neighbor would rather be the yellow cluster anemone (Parazoanthus axinellae), a colonial zoanthid (that is, belonging to the Hexacorallia) whose polyps are very similar although they don’t grow a proteinaceous hard and dark skeleton like the gold coral does. Notice that the yellow cluster anemone is usually found near our gold coral, just like in the video.

There is more to the affinity with the gorgonians. Indeed, you’ll almost always find gorgonians (Paramuricea clavata especially) where there’s a gold coral. This happens because if an elusive gold coral’s larva lands on top of a gorgonian or even of a black coral (Antipathella subpinnata) branch, it might implant there and start a not-so-slow conquest of it (see fig. below). From one initial polyp more will grow out of asexual reproduction, and so on until there’ll be no trace of the gorgonian: all of it will have been phagocytized!

Savalia savaglia Paramuricea clavata © Elisa Manganelli
Growth on a violescent sea-whip (Paramuricea clavata) substrate © Elisa Manganelli
Gold coral - Savalia savaglia © Elisa Manganelli
Portion of a large colony (another one can be seen at the back) © Elisa Manganelli

Then – surprise! – everything changes. The gold coral, left without an edible substrate, will grow extremely slowly (the radial growth figure is between 1 and 5 mm every 100 years) and will also start to reproduce sexually, spawning eggs and sperm in December to perpetuate the species. And you know what, a gold coral colony is entirely made of either male or female polyps (it’s a gonochoric species), which implies that the fecundation can only take place if the separate colonies are not so far away from each other – something quite rare, as already mentioned. The reproductive success, therefore, is very low. Luckily Mother Nature considered this, since a gold coral colony can live up to 3000 years, that is, many many reproductive essays more than the 25-year-old-max gorgonians.

Speaking of isolated colonies, there is of course some exception to the rule. The weirdest is the one in Kotor Bay, Montenegro, where in a rather small surface at a depth between only 10 and 20 m there are more than 300 colonies!
Not to mention one spot in our beloved Ustica, where at 30 meters you’ll find a wonderful and indeed mysterious succession of 11 big colonies (see fig. above), probably grown even without a gorgonian substrate at all! Sure it’s not 300, but you won’t believe when you’ll see it within our itinerary The Tuna Route.

Finally, Savalia savaglia is endemic to the Mediterranean. It’s found throughout the western basin, in the Sicily Channel (Pantelleria and Linosa), in the Adriatic Sea (Tremiti Islands and Montenegro at least), but also in the Aegean and Marmara Seas. Yet it was at some point able to cross the Gibraltar Strait, as in the Graciosa Island in the Canary archipelago many specimens can be observed.

In which itinerary do we spot it?