Actinocyclus curvatulus Janisch, 1874

Al-Handal, Adil Y., Thomas, Evan W. & Pennesi, Chiara, 2018, Marine benthic diatoms in the newly discovered coral reefs, off Basra coast, Southern Iraq, Phytotaxa 372 (2), pp. 111-152 : 116-117

Actinocyclus curvatulus Janisch in Schmidt et al. (1878: pl. 57:31) ( Fig. 11 )

References: Schmidt et al. 1878, pl. 57, fig. 31; Hustedt, 1930, fig. 307; Witkowski et al., 2000, p. 20, pl. 6, fig. 2.

Features: Diameter 40–65 μm.

Description: Valves circular and concave with rounded areolae decrease in size towards valve margin. Small pseudonodulus are visible near the valve margin.

Remarks: This species can be distinguished by the distinctly curved rows of areolae which decrease in size towards the margin and the marginal processes located at the end of each row (internal side of the valve). Marginal pseudonodulus may become indistinguishable. Areolae 6–8 in 10 μm near the center and 10–18 in 10 μm near the margin. Marginal process 10–12 in the observed specimens which is less than those reported elsewhere (12–18).

Ecology and Distribution: Widely distributed species, previously recorded from the Gulf ( Simonsen 1974, Al-Yamani & Saburova 2011). Frequent in Basra corals.

Figures

FIGURES 11–20. Marine benthic diatoms in the coral reefs off Basra. Fig. 11. Actinocyclus curvatulus, Fig. 12. Actinocyclus octonarius, Fig. 13. Lyrella abrupta, Fig. 14. Lyrella clavata, Fig. 15. Lyrella hennedyi, Fig. 16. Lyrella hennedyi var. subcarinata, Fig. 17, Lyrella spectabilis, Fig. 18. Petroneis granulata, Fig. 19. Petroneis marina, Fig. 20. Petroneis sp.