Alcyonium acaule is a coral belonging to the group of soft corals (order Alcyonacea), which together with 1,003 other species make up the family Alcyoniidae, in which there are 57 different genera. We will find this species predominantly in the Mediterranean Sea where it is considered to be endemic, although it is also possible to observe it in the immediate vicinity of the Atlantic Ocean and the Mediterranean Sea. The waters between 10 and 130 meters deep, and rocky areas where the specimens get indirect light, are the places where we can find specimens of this species.
This species of colonial coral forms elongated lobes, approximately 20 cm high, whose color can be yellow, pink, reddish or orange. Lacking an external calcareous skeleton, specimens of this species rely on internal hydrostatic pressure as well as spicules embedded in their tissue to keep the colony upright. From the most basal part of the colony to the most apical part, the body of Alcyonium acaule is completely covered with small whitish polyps 5 mm in diameter.
It can form large extensions where numerous individuals frequently coexist with specimens of Parazoanthus axinellae, and even with certain sponges, cnidarians, bryozoans and tunicates that form a true encrusting ecosystem of the rocky bottoms.
During the months of September and October is when the reproduction of Alcyonium acaule occurs. The male specimens release sperm that is captured by the females to fertilize their eggs, generating a larva that is subsequently released and will spend a few weeks drifting as part of the zooplankton, to later settle on the rocky bottom and start the formation of a new colony.
It is possible to confuse Alcyonium acaule with the species Alcyonium palmatum. The most obvious difference is the color of the polyps, white in the case of Alcyonium acaule, while the polyps of Alcyonium palmatum are translucent. The second aspect that will allow us to differentiate between these two species is the habitat in which we will find them. Alcyonium acaule lives exclusively on rocky bottoms, while Alcyonium palmatum lives on soft bottoms, especially sandy ones.
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