(Perag.) Hasle (1975: 124, figs 121–130)
Dactyliosolen mediterraneus (Perag.) Perag. (Peragallo, 1892: 104, pl. 33, figs 8, 9)Dactyliosolen mediterraneus var. tenuis Cleve (1897: 300, pl. 1, fig. 14)Dactyliosolen tenuis (Cleve) Gran (1902: 172)Dactyliosolen meleagris G.Karst. (Karsten, 1906: 160, pl. 29, fig. 2)
Lauderia mediterranea Perag. (Peragallo, 1888: 89, pl. 6, fig. 45)
Cupp (1943: 77, fig. 38), Priddle & Fryxell (1985: 62, figs A–D), Moisan & Fryxell (1993: 493), Hasle & Syvertsen (1997: 95, pl. 15a, b)
Cells solitary or united by valve faces into long chains, cylindrical, with coarsely structured and heavily silicified walls. Valves circular, flat; apical axis 7–35 µm, without spines or processes. Girdle bands numerous, 1–5 in 10 µm, punctate, the ends of the bands in a straight line along the long pervalvar axis (Fig. c). Cells weakly pigmented; chloroplasts rarely seen.
Sea-ice, inshore Davis Station, East Antarctica; Weddell Sea (Moisan & Fryxell, 1993); Weddell-Scotia Confluence (Garrison et al., 1987); Antarctic to the Arctic (Hasle & Syvertsen, 1997).
Chains of cells have often been illustrated with the epiphytic flagellate Rhizomonas setigera (Pavill.) D.J.Patt. et al. attached to the girdle band zone (e.g. Hasle & Syvertsen, 1997, fig. 15a). Observations suggest that the flagellated (or perhaps even amoeboid) stage emerges from the central area of the cell and covers frustules in large numbers in the spring. Rings of four flagellates on separate thecae could represent a later gametic stage. Further study is required, but it appears that R. setigera is a stage in the life cycle of L. mediterraneus rather than a distinct epiphyte. If so, the removal of L. mediterraneus from Dactyliosolen by Hasle (1975) is upheld, especially when one considers the life history of Dactyliosolen blavyanus (Perag.) Hasle as shown by von Stosch (1985).