Mastogloia stellae Pennesi & Poulin, 2013

Pennesi, Chiara, Poulin, Michel, Hinz, Friedel, Romagnoli, Tiziana, Stefano, Mario De & Totti, Cecilia, 2013, Comparison of two new species of Mastogloia (Bacillariophyceae) with other small members of section Ellipticae, Phytotaxa 126 (1), pp. 1-21 : 10-11

Mastogloia stellae Pennesi & Poulin , sp. nov. ( Figs 45–52 , SEM; Figs 57–60 , LM)

Diagnosis:— Valvae ellipticae vel late ellipticae, 11.8–25.6 µm longae, 6.2–11.3 µm latae, rotundis apicibus. Extra raphe duobus ramis sinuosis constitutum, quod in parte media expansis, in parte autem distali leviter expansis poris terminat; absunt terminales rimae. Interne raphe rectum est, densationibus circumscriptum. Raphe in parte media leviter elevato nodulo, in parte autem distali helictoglossa terminat. Transapicales striae radiales et uniseriatae (20– 25 in 10 µm), irregularem quincuncem structuram formantes. In externa parte areolae rotundae sunt, fixae in summa valva, paucis rotundis foraminibus. Partecta leviter bilobata, apicaliter extensa, similia in mensura (0.9 µm lata). Omne partectum in parte externa extensum porum habet.

Description:— Valves elliptical to broadly elliptical with rounded apices, 11.8–25.6 µm long and 6.2–11.3 µm wide ( Figs 45 , 57–60 ). Externally, two sinuous raphe branches end in expanded pores at centre and poles; no terminal fissure present ( Figs 45, 47 ). Internally, two straight raphe branches with raised central nodule and helictoglossae ( Figs 48–50 ). Transapical striae (20–25 in 10 µm) radiate at centre to curved radiate at poles, forming a quincunx pattern ( Figs 45–47 ). Striae composed externally of uniseriate rows of rounded areolae ( Fig. 45 ) sunken in the valve surface leaving only smaller foramina ( Figs 45–47, 52 ); no areolae on mantle ( Figs 51, 52 ). Internally, areolae open through small rounded foramina ( Figs 48–50 ) which form an irregular quincunx pattern ( Fig. 48 ). Three to five slightly bilobed partecta apically oriented ( Figs 48 , 57, 59 ) on each side of valvocopula, equal in shape and size (0.7–1.0 µm in width) and distributed along the whole length of the partectal ring up to the apex ( Figs 48 , arrowhead, 50, 57, 59); no septum hiding the helictoglossa ( Figs 48, 50 ). Each partectum is ornamented with small pores in parallel rows and opens externally through a partectal pore opposite to the concave side of the partectal lobe ( Figs 51 , arrowhead, 52).

Holotype:— Circled specimen on slide CANA 86492 ( Canadian Museum of Nature , Ottawa, Canada). The holotype specimen is illustrated in Figure 59 and 60 . SEM images of the type material are Figs 51 and 52 .

Isotype:— Circled specimen on SEM stub no. DISVAR-ANSH15SP31 (Department of Life Science and Environment, Polytechnical University of the Marche, Ancona, Italy).

Type locality:— EGYPT. Sharm el-Sheikh: in the Red Sea (27°51'16.71''N and 34°17'30.17''E). Epiphytic on Halophila stipulacea (Forsskål) Ascherson. Collected by Dr. Lucia Bongiorni, 1 February 2006 .

Etymology:— The specific epithet refers to the second author’s granddaughter, Stella Martineau-Poulin.

Figures

FIGURES 45–52. Mastogloia stellae, SEM, (45–50; DISVAR-ANS9SP31). (45) External view of valve showing sinuous raphe branches and irregular quincunx stria pattern; (46) External view of central region showing proximal raphe endings and sunken rounded areolae; (47) External view of apex showing distal raphe ending with no terminal fissure; (48) Internal valve view showing bilobed partecta (arrowhead) up to the apex; (49) Internal view of central region showing raised central nodule; (50) Internal view of apex showing helictoglossa and partecta with linear rows of fine pores. (51, 52) SEM, type material, (DISVAR-ANSH15SP31). (51) External view of tilted frustule showing partectal pores; (52) External view of valve margin showing sunken rounded areolae, with none present on mantle.

FIGURES 53–60. Type specimens in pairs of the new species of Mastogloia showing first the striation and second the partectal ring, LM. (53–56) M. matthaei, CANA 86491, holotype specimen in Figs 55, 56; (57–60) M. stellae, CANA 86492, holotype specimen in Figs 59, 60.