Sarcodictyon catenatum

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    S. catenatum
Stolonifero rosa
Fig. 1 © Elisa Manganelli
Stolonifero rosa
Fig. 2 © Elisa Manganelli

Sarcodictyon catenatum is neither large or gaudy and prefers the shades down to depths of around 100 m. Therefore you can be sure it’s there, right below or beside you, especially in underwater caverns, and what a pity if you missed its marvels!

It belongs to the anthozoan class, the so called «flower animals», which combine hard-corals, soft-corals (e.g. sea-whips), and sea anemones for their radial symmetry and their organ-less bodies. The genus stolonifera is then characterized by the presence of the stolon, a tissue that connects the polyps to form small colonies. In particular, in S. catenatum‘s colonies, amounting to up to 20 polyps, the single pink/reddish stolons sometimes blend into a common membranous structure, the coenosarc, able to fully cover rigid substrates (see Fig. 1).

Fig. 1: Filicudi, 40 m. Here S. catenatum took over a preexisting structure, colonized it, and ended up looking like a gorgonian branch.

Fig. 2: Ustica, 15 m, cavern. Stoloniferans love the shades. You can find them on the walls, on caverns’ roofs and on the underlying rocks.

Fig. 3: Ustica, 15 m, cavern. This is an excellent example of symbiosis, we can’t really tell whether mutualistic or commensal:

    • if this were the case of mutualistic symbiosis, S. catenatum‘s nettling proprieties would protect the spider crab from possible predators while for the former more feeding opportunities arise from being carried around;
    • in the case of commensal symbiosis, only S. catenatum takes advantage of the situation without damaging the spider crab.
Stolonifero rosa on spider crab
Fig. 3 © Elisa Manganelli

In which itinerary do we spot it?