Padina gymnospora

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 : 210

Padina gymnospora ( Fig. 3 A–D )

Basionym:— Zonaria gymnospora Kützing (1859: 29)

Type locality:—VIRGIN ISLAND. St. Thomas (Herb. Sonder)

Distribution in the Mediterranean Sea:— ITALY ( Sortino 1967 as P. gymnospora sensu Vickers )

Examined Specimens:— ITALY. Agrigento: Palma di Montechiaro, – 0.5 m, 2/1/1967, CAT 1735 as P. pavonica cfr. gymnospora .

Morphology:—The thallus is fan-shaped ( Fig. 3A ), not or slightly calcified in the upper surface, and attached to the substrate with a rhizomatous holdfast. It has a smooth surface, with margins slightly undulated and a rolled apical portion. The hair lines are concentric, distributed at equal distances and are not prominent. They are present on both surfaces and are more conspicuous on the lower portion of the thallus. The species has 2 cell layers in the rolled apical portion ( Fig. 3B ), but immediately the layers become 3–4 ( Fig. 3B, C ) and up to 6–8 in the basal portion ( Fig. 3D ). In our samples, no reproductive traits were found.

Remarks:—The only report of P. gymnospora in Mediterranean Sea ( Sortino 1967) refers to P. gymnospora sensu Vickers ; but, this record probably should be considered as a misidentification of the tristromatic species P. boergesenii , as also assumed by Furnari et al. (2010) and Ni-Ni-Win et al. (2011a).

However, the herbarium specimen that we examined was collected in the same locality as the specimens reported by Sortino (1967). That specimen shows all the features of P. gymnospora (Kützing) Sonder (non Vickers) as reported by Womersley (1987) and by Allander & Kraft (1983:87) that examined the holotype of Zonaria gymnospora (MEL 583380 in the Sonder collection) when they described the new species Padina boergesenii . Therefore, this is the first supported record of P. gymnospora for the Mediterranean Sea.

Figures

FIGURE 3. Padina gymnospora. A. Herbarium sheet (CAT 1735) showing the habitus. B. Longitudinal section of the rolled part of the apical portion of the thallus shows 2 cell layers in the rolled part and the transition to 3 cells (pointed by the arrow). C. Cross section of the median portion of the thallus showing 4 layers of cells. D. Cross section of the basal portion of the thallus showing 6–8 layers of cells. All photos refer to the herbarium sheet sample. Scale bars: A, 1,5 cm; B–D, 50 μm. Photos by G. Marletta.