Padina ditristromatica

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 : 208-210

Padina ditristromatica ( Fig. 2 A–E )

Basionym:— Padina ditristromatica

Type locality:— ITALY. Syracuse : Brucoli, Augusta

Distribution in the Mediterranean Sea:— GREECE (Ni-Ni-Win et al. 2011a, Catra & Alongi 2013, Tsiamis et al. 2013). ITALY (Ni-Ni-Win et al. 2011 a, Bottalico et al. 2016). SPAIN ( Gómez Gómez et al. 2015). SYRIA ( Arraj et al. 2016). TURKEY (Ni-Ni-Win et al. 2011a).

Examined Specimens:— ITALY. Catania : Santa Tecla, Acireale, – 13.4m, – 23.9m, 02/07/2021 ; ITALY. Syracuse : Marzamemi, – 2m, 27/07/1969, CAT1110 as P. pavonica .

Morphology:—the thallus is flabelliform and subdivided into lobes ( Fig. 2A ). It is fixed to the substrate through a tangle of fibrous rhizoid filaments, which cover the lower surface of the basal portion ( Fig. 2A ). This species has calcified striae on both surfaces, except on the hair lines. The latter, concentrically arranged, are alternate on both surfaces and are spaced unequally ( Fig. 2B ), they are also narrow-undepressed on the upper surface and broad-depressed on the lower surface. The rolled part of the apical portion shows 2 layers of cells ( Fig. 2C ), while the median and basal portions feature a mixture of 2–3 cell layers, since some cells divide transversally ( Fig. 2D, E ). In the 2-layered region, the cells of the upper side are twice as high as those of the lower side ( Fig. 2C ), while in the 3-layered region portion, all three layers show the same height ( Fig. 2D, E ). In our samples, no reproductive traits were found.

Remarks:—this species was described by Ni-Ni-Win et al. (2011a) on specimens collected at Brucoli (eastern coast of Sicily) and after that, there have been no further reports along the Sicilian coasts. Our records extend the distribution range also in areas contiguous to the type locality both northward (Santa Tecla-Acireale) and southward (Marzamemi—Syracuse); in particular, the latter is based on the re-examination of the herbarium sample from 1969, labelled as P. pavonica .

Although P. ditristromatica has been reported both in the eastern and western Mediterranean basin, it is very likely that this species may have a wider distribution throughout the Mediterranean Sea, due to a possible misidentification with P. pavonica .

1 this paper; 2 Abbas & Shameel (2013a); 3 Abbas & Shameel (2013b); 4 Aisha & Shameel (2010); 5 Cormaci et al. (2012); 6 Gaillard (1967); 7 Gómez Gómez et al. (2015); 8 Huisman (2015); 9 Ni-Ni-Win et al. (2011); 10 Ni-Ni-Win et al. (2013); 11 Peralta (2013); 12 Womersley (1987)

Finally, until now, P. distristromatica has been reported in both low midlittoral and infralittoral zones up to – 7m ( Gómez Gómez et al. 2015); in this study, we observed that P. ditristromatica can extend to a depth of about – 24m.

Figures

FIGURE 2. Padina ditristromatica. A. Herbarium sheet (CAT 1110) showing the habitus. B. Upper surface with hair lines distributed in unequal distance C. Longitudinal section of the rolled part of the apical portion of the thallus showing 2 layers of cells. D. Cross section of the middle portion, showing a mixture of 2 (pointed by the arrows) to 3 layers (pointed by the arrowheads). E. Cross section of the basal portion of the thallus showing 2–3 layers of cells (pointed by the arrows). Photo A refers to the herbarium sheet sample. Photos B to E refer to the Santa Tecla (CT) sample. Scale bars: A, B, 1 cm; C–E, 50 μm. Photos by G. Marletta.