Pinnunavis yarrensis (Grunow) H. Okuno

Lobban, Christopher S., 2015, Benthic marine diatom flora of Guam: new records, redescription of Psammodictyon pustulatum n. comb., n. stat., and three new species (Colliculoamphora gabgabensis, Lauderia excentrica, and Rhoiconeis pagoensis), Micronesica 2015 (2), pp. 1-49 : 10-11

Pinnunavis yarrensis (Grunow) H. Okuno Figs 98–105

Syn.: Pinnularia yarrensis (Grunow) Jurilj , Navicula yarrensis Grunow

Naviculales : Naviculaceae .

Ref. illus.: Grunow in Schmidt et al. 1874–1959, pl. 46, figs 1–6; Meister 1932, pl. 17, fig. 139; Hustedt 1955, pl. 9, fig. 2; Navarro 1983a, figs 108–110; Wah & Wee 1988, fig. 64 (all as Navicula yarrensis ); Witkowski et al. 2000, pl. 146, fig. 11; López-Fuerte et al. 2010, pl. 29, figs 1, 2 (both as Pinnularia yarrensis ); Okuno, 1975, fig. 8-2 and 2a

Samples: GU69A-1

Dimensions: 36–105 µm long, 15–32 µm wide, 4–7 striae in 10 µm.

Diagnostics: Striae radiate along most of the valve but convergent at the apices. Striae consisting of single alveolus with numerous small poroids in the outer membrane and no inner membrane ( Figs 102–104). The two plastids ( Fig. 98) extend onto the valve face nearly to the raphe, with closely lobed margins. Valve shape varied from elliptical-lanceolate to linear with broadly rounded apices; size also varied widely in this population.

Comments: SEM views confirm the images shown by Navarro (1983a). I also noted that the inner margin of the valvocopula is scalloped to fit against the outer edges of the interstriae ( Fig. 105). There is a single line of pores near the abvalvar edge of the wide valvocopula ( Fig. 103).

A “striking species of massive sculpture” ( Mann 1925:125), and equally handsome alive. This species is usually noted as widespread but scarce ( Hustedt 1955:32; Witkowski et al. 2000:338), but was abundant in GU69A-1 from surface sediment at the edge of a mangrove. Navarro (1982a), Wah & Wee (1988) and López-Fuerte et al. (2010) also reported it from mangroves. Meister (1932:43) reported linear valves of the nominate variety from Cavite Bay, Luzon, Philippines (habitat not given). The number of striae reported varies from 3–3.5 in 10 µm ( Meister 1932) and 4 in 10 µm ( Witkowski et al. 2000), to 10 in 10 µm ( Podzorski & Håkansson 1987); the more finely striate forms are not so readily distinguished from Navicula . In my sample, the smaller valves ( Fig. 104) had denser striae but appear to still be the same species. Length range in the literature is 60–200 µm ( Witkowski et al. 2000); the smallest valve I found was 36 µm long. Several varieties have been named, including three from Miocene deposits ( Hajós 1968; California Academy of Sciences 2011). Navicula yarrensis was first transferred to Pinnularia ( Jurilj 1957) and later to a new genus, Pinnunavis Okuno (1975) , along with P. elegans (W. Smith) Okuno , and this is the currently accepted name for P. yarrensis according to AlgaeBase ( Guiry & Guiry 2014). However, Pinnunavis elegans (W. Smith) Okuno was transferred back to Pinnularia by Krammer (1992). The plastids of P. elegans lie along the girdle bands, typical of Navicula and Pinnularia (A. Witkowski, personal communication), whereas those seen here for P. yarrensis spread across the valve face, more like those of some Diploneis . It remains to be seen how these genera are related molecularly.