Naviculaceaea Kützing

Al-Handal, Adil Y., Compère, Pierre & Criobe-Usr, Catherine Riaux-Gobin, 2016, Marine benthic diatoms in the coral reefs of Reunion and Rodrigues Islands, West Indian Ocean, Micronesica 2016 (3), pp. 1-78 : 27

Family Naviculaceaea Kützing

Amicula cf. specululum (Witkowski) Witkowski (Pl. 13, Fig. 7) References: Witkowski et al. 2000, p. 127, pl. 65, figs 1-14.

Features: Apical axis: 8-9 µm, transapical axis: 3-4 µm, striae 38 in 10 µm. Valves broadly elliptic with round apices. Valve surface almost flat, raphe straight with straight terminal raphe endings positioned far from the margin. Striae parallel in mid-valve, strongly radiate near the apices and limited to marginal part of the valve.

Remarks: Similar to A. specululum illustrated in Witkowski et al. (2000) but differs in the length of striae (longer in our specimens) and stria density (38 in 10 µm versus 30 in A. specululum ). Occurrence: Rare in Reunion Island.

Haslea nautica (Cholnoky) Giffen (Pl. 9, Fig. 4) References: Giffen 1980, p. 146, fig. 64; Witkowski et al. 2000, p. 224, pl. 148, figs 9-11. Features: Apical axis: 64-80 µm, transapical axis: 10-15 µm, striae 16-18 in 10 µm. Valves lanceolate with sub-acute apices. Raphe straight and lacking central area, axial area narrow. Striae composed of rectangular poroids separated from each other by hyaline areas along axial rows. Remarks: Only large specimens were observed in the Indian Ocean material. Stria density is slightly higher than that reported by the above mentioned references but corresponds with that given by Lobban et al. (2012) from Guam (Pacific Ocean). Widely distributed species in marine and brackish waters.

Occurrence: Rare in Reunion and Rodrigues Islands. Previously reported from Seychelles (G).

Hippodonta sp. (Pl. 14, Fig. 6) Features: Valves elliptic to linear elliptic with round apices, 7-9 µm long, 2-2.5 µm wide. Axial area very narrow, central area rectangular and developed in a fascia delineated by one short stria on both sides of the valve. Raphe straight, terminal raphe endings terminate at some distance from the apices, slightly deflected to one direction. Striae parallel, formed of slightly apically elongate areolae, 18-20 in 10 µm.

Remarks: Several Hippodonta species of very small size were observed under SEM, but identification was not possible due to insufficient material.

Occurrence: Rare in Reunion and in Rodrigues Islands.

Navicula cf. arenaria var. rostellata Lange-Bertalot (Pl. 5, Fig. 8) References: Krammer & Lange-Bertalot 1986, p. 118, pl. 39, fig. 2; Witkowski et al. 2000, p. 267, pl. 116, figs 19-21, pl. 129, fig. 29.

Features: Apical axis: 32-46 µm, transapical axis: 7-9 µm, striae 11-13 in 10 µm. Valves linear lanceolate with produced apices. Raphe straight, axial area very narrow, central area nearly rectangular and occupying half width of the valve. Striae slightly curved in mid-valve, becoming parallel towards the apices.