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70 Gianmarco Ingrosso et al.

occur on Tyrrhenian, Ionian and southern Adriatic shores (Fig. 2B), but
have a circumscribed distribution, limited to stretches ranging from tens
of metres to a few kilometres. When present, L. byssoides rims usually are
not continuous along the shoreline but are best developed in inlets, crevices
or other spots that provide partially shaded conditions and some shelter from
wave action. A preference of this alga for calcareous rocks over granites and
schists has been noted in some areas (Cossu and Gazale, 1997). In Italy, these
bioconstructions reach their maximal extent in northwestern Sardinia,
where rims can be wider than 2m (Cossu and Gazale, 1997).

2.2.2 Astroides calycularis Formations/Reefs
The orange coral Astroides calycularis (Pallas, 1766) is an azooxanthellate
dendrophylliid coral with a calcium carbonate exoskeleton, endemic to the
Mediterranean Sea (Zibrowius, 1980, 1983; Fig. 2). It inhabits rocky shores
from the surface to 50m depth (Ocan ˜aet al., 2000; Rossi, 1971) but is typ-
ically found in the shallow infralittoral zone (0–15m depth), on vertical walls
or inside caves (Cinelli et al., 1977; Kruz ˇίc et al., 2002; Zibrowius, 1978); in
the latter habitat, it can exhibit great size and cover (Morri et al., 1994a).
This scleractinian coral is considered a reef-forming species (European
Commission, 2013) since its bioconstructions cover up to 90% of some rocky
areas in shallow waters (Goffredo et al., 2011) and host a rich invertebrate
fauna. In the southern coast of the Iberian Peninsula, Terro ´n-Sigler et al.
(2014) found 81 macroinvertebrate species (mainly crustaceans, annelids
and molluscs) associated with A. calycularis colonies.
A. calycularis mostly occurs in the south-western part of the basin from the
Straits of Gibraltar to Sicily (Terro ´n-Sigler et al., 2016a). Musco et al. (2016)
report a list of five hot spot areas, in the south-western coast of the Italian
peninsula, where A. calycularis reefs appear more developed (Fig. 2C),
namely: (1) the Sorrento Peninsula and the islands of Ischia and Capri,
(2) the Cilento coast, (3) the Strait of Messina and the Aeolian Islands,
(4) the north-western coast of Sicily and (5) Pantelleria and the Pelagie Islands
in the Strait of Sicily. In the Adriatic Sea, the species is present with sparse
colonies along the Croatian coast only (Grubelic et al., 2004; Kruz ˇίc et al.,
2002); some sporadic records along the Italian side need confirmation.
The northernmost record along the Italian coast is of a dead colony at Giglio
Island (Bianchi and Morri, 1994). The northern limit of stable reef-forming
populations is at Ventotene (Pontine Islands), while the southern limit is in
the Pelagie Islands (Musco et al., 2016).