Padina pavonica (Fig. 4 A–G)

Basionym:— Fucus pavonicus Linnaeus (1753: 1162)

Type locality:— In mari Europae australis

Distribution in the Mediterranean Sea:—This species is widely distributed in Mediterranean ITALY, SPAIN, GREECE, FRANCE, MALTA, MOROCCO, ALGERIA, TUNISIA, LIBYA, EGYPT, ISRAEL, SYRIA, LEBANON, TURKEY (Guiry & Guiry 2023).

Examined Specimens:— ITALY. Catania: Aci Trezza, Aci Castello, – 5 m, 25/04/22; ITALY. Syracuse: Penisola Magnisi, Priolo, –0,5 m, 16/06/22; ITALY. Messina: Milazzo, –0,5 m, 14/06/22; ITALY. Messina: Canne d’Organo, Filicudi Island, –0,5 m, 09/07/22; ITALY. Trapani: Cala Tramontana, Kattibuale, Scauri, Pantelleria Island, –0,5 m, 23/03/22; ITALY. Trapani: Macari, – 0.5m, 06/10/2022; ITALY. Palermo: Punta Raisi, – 0.5m, 07/10/2022; ITALY. Trapani: Cala Levante, Pantelleria Island, – 5 m, 05/09/1970, CAT1733 and CAT1734; ITALY. Syracuse, Brucoli, Augusta, –0,5 m, 25/01/1970, CAT1104; ITALY. Palermo: Ustica, – 10 m, 04/07/1967, CAT1732; ITALY. Messina: Lipari Island, – 4 m, 18/05/1969, CAT1729; ITALY. Caltanissetta: Gela, –0,5 m, 29/07/1968, CAT1111; ITALY. Agrigento: Palma di Montechiaro, – 1 m, 18/10/1966, CAT1722; ITALY. Messina: Capo Milazzo, – 4 m, 04/04/1969, CAT1728; ITALY. Palermo: Capo Zafferano, – 8m, 07/06/1969, CAT1727; ITALY. Syracuse: Ognina, –0,5 m, 12/06/1970, CAT1096.

Morphology:—The thallus is semicircular to circular with radial lacerations, low or not calcified on the lower surface and moderately calcified on the upper surface. It is fixed to the substrate with dense tufts of rhizoids (Fig. 4A). The hair lines are concentric, alternate between both the surfaces of the thallus and are disposed at equal distances. They are narrow-undepressed in both the surfaced. This species shows 2 cell layers in the rolled part of the apical region (Fig. 4C), 3 cell layers in the median portion (Fig. 4D) and 3–4 cell layers at the base (Fig. 4E). The medullary layers (1–2) consist of cells larger and less pigmented than the cells of the two peripheral layers (Fig. 4D). In some of our specimens (Cala Tramontana and Kattibuale in Pantelleria Island, in Filicudi Island, and Punta Raisi), the presence of the Vaughaniella stage was found (Fig. 4A, F). This finding agrees with the observations of Peralta (2013) and Gómez Gómez et al. (2015), which reported the presence of this stage in P. pavonica.

The sporangial cysts are grouped in sori, which are obovate with a basal pedicel and a transparent indusium (Fig. 4B). They are distributed only on the lower surface and form continuous lines on both sides of the hair lines, particularly they are broad above hair lines and narrow below hair lines (Fig. 4B).

Remarks:—Our observations confirm the wide distribution of the species in the Mediterranean Sea. However, as was often the case previously, the identification of this species should not be taken for granted given its similarity to other species of the genus.