Synedrosphenia licmophoropsis 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 licmophoropsis Lobban sp. nov.

Figs 9 , 10

Diagnosis.

Extremely long heteropolar cells, differing from other species in the cuneate shape in valve and girdle views.

Description.

Frustules heteropolar, tapering uniformly in both valve and girdle view (Figs 9D , 10A, B ), attached to seaweed substrata by mucilage stalks; plastids numerous, lenticular to oval (Fig. 9A, B ). Valve margins parallel near basal pole, 14 µm wide, widening evenly to 27 µm wide just before the cuneate obtuse or slightly rostrate apical pole, length 600-735 µm (Fig. 9A-D ). Striae parallel except radiate near apical pole, 19 in 10 µm near the apical pole, 16-17 near the basal pole (Fig. 9E-H ). Annulus, evident even in living specimens (Fig. 9A ), nearly halfway between centerline and valve margin (Fig. 9B-H ), underlain by a longitudinal costa except at apical pole (Fig. 9G, H ). Valve border with a rim along its length and shallow pseudosepta at each pole (Fig. 9G, H ), the latter matched by extensive development of the valvocopula. In girdle view, three bands evident, all fimbriate (Fig. 10A-C, F ). Valvocopula bearing a row of pores at the edge of the pars interior and five rows of pores on the exterior near the apical pole, reduced to two near the basal pole, the pores in a decussate pattern, 27 in 10 µm, the edge of the pars interior bearing short fimbriae near the apical pole, longer elsewhere (Fig. 10D-F ). The pars interior of the valvocopula at the poles formed a deep shelf with an irregular surface (Fig. 10D, E ), creating a notch on one side and a shallower, longer gap on the other (Fig. 10A, B ); notches were on opposite sides of both the valvocopula itself and when comparing epitheca and hypotheca (Fig. 10A, B arrows). The line of pores along the edge of pars exterior moved to inner edge of the gap and became slitlike (Fig. 10G , arrow). Copula (Fig. 10A, B, F, H ) wider, again with pores in a decussate pattern, about 10 rows near apical pole diminishing to five at the basal pole, a wide delicate fringe along the edge of the pars interior. The relationship between the first two girdle bands at the poles is shown in Fig. 10I . The pleura (Fig. 10A-C ) had a broad apical cap, quickly tapering to a narrow external line with fimbriate pars interior, broadening again somewhat at the basal pole; this band lacked pores.

Holotype

(designated here). Specimen at 13.0 mm E and 5.0 mm S of the mark on slide 455, deposited at ANSP accession # ANSP-GC20086. Fig. 9B-D .

Registration.

Phycobank http://phycobank.org/103237.

Type locality.

“Pete’s Reef" (commercial dive site), Agat Bay, 13.347°N, 144.639°E. Epiphytic on Halimeda at 10 m, collection number GU55B-4, 13 Dec. 2008. C. Lobban and M. Schefter, leg.

Additional materials examined.

Guam: GU44Y-13!, GU44AV-8!, GU54A-B!, GU56A-2!, GU66B-6!, GU76B-2. Federated States of Micronesia: Yap: Y-37-8!; Marshall Islands: Bikar Atoll BA-5!.

Etymology.

Named for its resemblance to certain large Licmophora spp., especially L. attenuata Lobban, Tharngan and Ashworth.

Taxonomic comments.

Longer and more evenly tapered, apical pole broadly rounded, striae denser compared to S. gomphonema ; valves appearing narrower than S. gomphonema because of the greater length, but the apical poles are equally wide.

Figures

Figure 9. Synedrosphenia licmophoropsis sp. nov. A apical pole of living cell showing plastids and annulus (arrow) (GU 44 AV- 8) B-D holotype valve from GU 55 B- 4 in LM: apical and basal portions showing annulus and entire valve E, F external view of valve, SEM: basal and apical poles, respectively, same scale (GU 44 Y- 13) G, H apical and basal poles, respectively, valve in internal view, SEM, showing longitudinal and transverse costae and pseudosepta (arrows) (GU 56 A- 2). Scale bars: 50 µm (D); 10 µm (A-C, E-G); 5 µm (H).

Figure 10. Synedrosphenia licmophoropsis sp. nov., girdle bands A, B frustule in girdle view with thecal elements labeled, respectively on the apical part and the basal pole of the same cell also showing the asymmetrical apical notches in the valvocopula (arrows) (GU 55 D- 3) C small portion near middle of frustule where pleura (pl) is exposed (GU 76 B- 2) D, E basal pole of valvocopulae at 0 ° tilt with opposite valve in the background and tilted to show complex shape of the pars interior, arrowhead pointing toward notch (GU 76 B- 2 and TK 4, respectively) F portions of valvocopula and copula showing fimbriate inner edges (GU 55 D- 3) G valvocopula, apical pole in abvalvar aspect with attached valve, showing elongated pores on inner edge (arrow) (GU 44 BJ- 2) H apical portion of copula showing very long fimbriae at the tip (arrow) (GU 55 D- 3) I relationship between first two girdle bands at basal pole, the long fimbriae of the copula overlapping the valvocopula (GU 76 B- 2). Scale bars: 10 µm (A, B, F, H); 5 µm (C-E, G, I).