Padina pavonicoides, Ni-Ni-Win & H.Kawai, 2011

Pagana, Ilaria, Marroccia, Genny, Marletta, Giuliana & Alongi, Giuseppina, 2023, Re-examination of the distribution and species diversity of the genus Padina (Dictyotales, Phaeophyceae) in the Mediterranean Sea, Phytotaxa 619 (3), pp. 205-218 : 212-213

Padina pavonicoides ( Fig. 5 A–G )

Basionym:— Padina pavonicoides

Type locality:— FRANCE. Cannes : Port Cap de la Croisette.

Distribution in the Mediterranean Sea:— FRANCE (Ni-Ni-Win et al. 2011a). SPAIN (Ni-Ni-Win et al. 2011 a, Gómez Gómez et al. 2015). TURKEY ( Taskin 2013).

Examined Specimens:— ITALY. Syracuse: Brucoli, Augusta, –0,5 m, 21/05/21 ; ITALY. Catania: Santa Tecla, Acireale, –9,5 m, 02/07/21 ; ITALY. Trapani: Martingana and Scauri, Pantelleria Island, –0,5 m, 23/03/22 .

Morphology:—The thallus is semicircular to circular with entire margin, low or not calcified on the lower surface and slightly calcified on the upper surface. It is fixed to the substrate with a short stipe, covered on the lower surface by rhizoid filaments ( Fig. 5A ). The hair lines are concentric, alternate between both the surfaces of the thallus and are disposed at equal distances ( Fig. 5B ). They are narrow-undepressed in the upper surface and broad-slightly depressed in the lower surface. This species has mainly 3 layers of cells ( Fig. 5E, F ), except for the rolled apical portion, which has 2 layers of cells ( Fig. 5D ). In the 3-layered parts, the cells of the central layer are nearly twice as high as those of the surface layers ( Fig. 5E, F ). In the specimens collected at Martingana, we found the Vaughaniella stage ( Fig. 5G ).

The sporangial cysts are grouped in sori, which are obovate and with a transparent indusium ( Fig. 5C ) and are distributed only on the lower surface and form patches above the hair lines ( Fig. 5B ).

Remarks:—Until today, P. pavonicoides has been found only in Turkey, Spain and France. Our Sicilian records expand the distribution area of this species and show an effective continuity between the eastern and western basin. It should be noted that we collected P. pavonicoides also in shallow habitats, expanding the bathymetric distribution range of the species compared to what was suggested by Gómez Gómez et al. (2015).

Figures

FIGURE 5. Padina pavonicoides. A. Habitus of P. pavonicoides. B. Lower surface with sporangial sori in patches above hair lines, arranged at equal distance C. Section of tetrasporangial sori covered with an indusium (pointed by the arrow). D. Longitudinal section of the rolled apical portion of the thallus showing 2 layers of cells. E. Cross section of the median portion of the thallus showing 3 layers of cells. F. Cross section of the basal portion of the thallus showing 3 layers of cells. G. Cross section of Vauganiella stage. Photos A, D, and F refer to the sample of Brucoli (SR), photo G refers to the sample of Martingana—Pantelleria, and photos B, C and E refer to the sample of Scauri—Pantelleria. Scale bars:A, 1 cm; B, 0,5 cm; C–G, 50 μm. Photos by G. Marletta.