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.