Mayamaea sardiniensis G.G. Lai & C.E.Wetzel, 2025

Lai, Giuseppina G., Padedda, Bachisio M. & Wetzel, Carlos E., 2025, Mayamaea sardiniensis sp. nov. (Bacillariophyceae), a new species from a thermo-mineral spring in Sardinia, Italy, Phytotaxa 696 (2), pp. 169-180 : 172

Mayamaea sardiniensis G.G. Lai & C.E.Wetzel sp. nov. ( Figs 2–27 )

Light microscopy ( Figs 2–21 ):— Valves elliptical to oval, with broadly rounded apices, never protracted. Valve dimensions (n = 30): length 5.1–11.5 µm (7.4 ± 1.8 µm), width 2.5–3.0 μm (2.8 ± 0.2 µm). Raphe branches filiform, slightly curved toward the ventral side of the valve, with polar and central nodules visible as white or dark dots ( Figs 1 , 3 ). Striae: 30–32 striae in 10 μm, hardly discernible and shortened in the middle of the valve ( Figs 3, 9 ).

Scanning electron microscopy ( Figs 22–27 ):— Axial area narrow, linear. Central area wide and symmetrical, rectangularly shaped, bordered by 2–3 shortened striae. Raphe filiform with short, straight or weakly deflected external proximal raphe endings ( Fig 23 ). Distal external raphe fissures hooked and deflected to the same side of the valve ( Figs 22, 23 ). Internally, proximal raphe endings straight or slightly deflected and distal raphe endings terminating in small helictoglossae ( Fig 26 ). Striae uniseriate, parallel or weakly radiate throughout and shortened in the middle of the valve, composed of 2 to 4 areolae rounded areolae, covered externally by porous hymens, and interrupted by a hyaline line at the valve face/mantle junction ( Figs 22, 23 ).

Type: Locality— ITALY. Benetutti : San Saturnino, 252 m a.s.l., 40°25’24.2’’N, 009°07’17.6’’E), Habitat: epipelon, Sampling date: 03 July 2016, sample collected by Giuseppina Grazia Lai, Holotype: Permanent slide n° BR-4684 deposited in the Diatom Collection of the Meise Botanic Garden, Belgium, specimen depicted in Figs 2, 3 .

Etymology:— The specific epithet refers to the Mediterranean island of Sardinia.

Figures

FIGURE 1. a) Geographic position of Sardinia (Italy), b) location of the spring San Saturnino, c) water abstraction system at the emergent point of the spring, d) spring-fed rivulet.

FIGURES 2–27. Mayamaea sardiniensis G.G. Lai & C.E. Wetzel sp. nov. Figs 2–21: LM images of the type population from the spring San Saturnino, Sardinia (Italy). Figs 22–23: SEM external view showing the raphe and striae structure. Fig 22: SEM external view of a valve showing areolae with the hymenate occlusions. Fig 23: SEM external view of an eroded valve without hymenate occlusions on some areolae. Note the interruption of the strie by a hyaline line at the valve face/mantle junction. Figs 24–27: SEM internal view showing small helictoglossae at the poles and slightly deflected proximal raphe ends.