Synedrosphenia parva Lobban, 2022

Lobban, Christopher S., Ashworth, Matt P., Camacho, Terance, Lam, Daryl W. & Theriot, Edward C., 2022, Revision of Ardissoneaceae (Bacillariophyta, Mediophyceae) from Micronesian populations, with descriptions of two new genera, Ardissoneopsis and Grunowago, and new species in Ardissonea, Synedrosphenia and Climacosphenia, PhytoKeys 208, pp. 103-184 : 103

Synedrosphenia parva Lobban sp. nov.

Figs 11 , 12

Diagnosis.

Shorter and narrower than S. gomphonema and more finely striated. Girdle bands distinctive: copula with very long internal fimbriae at poles, pleura a large apical cap.

Description.

Frustules heteropolar in valve and girdle views (Fig. 11A, F, G ) with numerous small plastids (not shown). Valves 196-250 µm long, 18 µm wide near the apical pole, clavate with acutely rounded to weakly rostrate apical poles (Fig. 11A-E ). The annulus evident in LM but close to edge of valve face (Fig. 11A, C ). Valve surface with weak longitudinal furrows, mantle deeper toward apical pole (ca. 11 vs. 5 areolae deep) (Fig. 11 B, C, F, G ). Striae 16 in 10 µm near basal pole, 18-20 in 10 µm near apical pole, parallel except radiate at apical pole (Fig. 11A-E ). Pseudosepta present at both poles (Fig. 11D, E ); longitudinal costae subtending annulus and transverse costae on vimenes except at apical pole (Fig. 11D, E ). Three girdle bands are present (Figs 11F, G , 12E-G ). Valvocopula with a row of pores along outer edge of pars interior plus three rows decreasing to one on pars exterior; pars interior with a notched flange at each pole and a fimbriate edge (Fig. 12B ). Copula with up to nine rows of pores at apical pole in decussate pattern, decreasing to three near basal pole (Figs 11F, G , 12C, D ). Pleurae a pair of polar caps (connecting band not seen), the apical cap relatively massive with small pores and fimbriate (Figs 11F , 12E-G ), basal cap smaller, with fewer pores (Fig. 11G arrowhead).

Holotype

(designated here). Specimen at 15.3 mm E and 12.7 mm S of the mark on slide 2326, deposited at ANSP accession # ANSP-GC20088. Fig. 11A .

Registration.

Phycobank http://phycobank.org/103238.

Type locality.

Agat Reef behind Anae I., Agat Bay, 13.357°N, 144.645°E. Epiphytic on seaweed at low tide line, collection number GU75A-4, 6 May 2017. C. Lobban and M. Schefter leg.

Additional materials examined.

F.S.M.: Chuuk, TK4!; Marshall Islands. Jaluit Atoll, J5!.

Etymology.

Named for its small size within the genus.

Figures

Figure 11. Synedrosphenia parva sp. nov. A holotype from Guam in LM, arrow indicates annulus near valve face-mantle junction (GU 75 A- 4) B, C valve in external view (SEM), basal and apical poles, respectively, arrow indicates annulus (GU 75 A- 4) D, E internal views of apical and basal poles, respectively, arrows indicate pseudoseptum (J 5) F, G frustule in girdle view, apical and basal portions, respectively, showing the girdle bands including the large apical cap of the pleura, smaller at the basal pole and perhaps not connected (arrowhead in G indicates the apparent end of the pleura); arrows on F, G point to polar notches (GU 75 A- 4). Scale bars: 25 µm (A); 10 µm (B, C, F, G); 5 µm (D, E).

Figure 12. Synedrosphenia parva sp. nov., cont. All GU 75 A- 4 A, B valvocopula showing apical internal side from abvalvar position, and portion of middle from advalvar side, respectively, showing row of pores along base of pars interior and fimbriae C internal view of apical pole with valvocopula in situ and the copula, broken in the middle, covering the valvocopula around the apical pole and left side D basal pole of same specimen, again showing the long fimbriae overlapping the valvocopula E, F frustules tilted to show polar (apical) architecture of, respectively a recently divided cell, where the pleura is in place between the copulae of the two cingula, and a non-dividing cell G detail of a pleura loosened from its position and showing some of the fimbriae (still tucked under the copula at top of image). Scale bars: 10 µm (A); 5 µm (B, D-F); 2.5 µm (C, D, G).