DIATOMS IRELAND
Navicula Bory de St. Vincent (1822)
Dict. Class. Hist. Nat. 2: 128
Cells solitary, usually seen in valve view and often actively motile when live. Live cells with two plate-like chloroplasts lying along each side of girdle, each with a single rod-shaped pyrenoid along their length (only visible in girdle view). Valves variable in outline, usually linear-lanceolate to lanceolate, with variously shaped apices. Raphe central, fissures usually hooked over valve apices, slightly expanded at centre. Stria path variable, striae usually cross-lineate, i.e. containing linear pores at right angles to the direction of the stria. Girdle usually narrow, comprised of a few plain bands.
Some of the taxa included in this genus are not closely related to Navicula tripunctata, and have been placed in other genera by different authors.
M.G. Kelly, H. Bennion, E.J. Cox, B. Goldsmith, J. Jamieson, S. Juggins D.G. Mann & R.J. Telford (2005). Common freshwater diatoms of Britain and Ireland: an interactive key. Environment Agency, Bristol.
Species described:-
Navicula sp. nr..gregaria Donkin
Navicula oblonga (Kützing) Kützing
Navicula oppugnata Hustedt
Navicula peregrina (Ehrenberg) Kützing
Navicula radiosa Kützing
Navicula rhynchotella Lange-Bertalot
Navicula slesvicensis Grunow in Van Heurck
Navicula vaneei Lange-Bertalot in Witkowski et al.
Navicula viridula Kützing
Navicula oblonga (Kützing) Kützing
Cells narrowly rectangular in girdle view with somewhat rounded corners, the central and polar raphe thickenings clearly visible. Valves linear, sometimes slightly gibbous at the centre, with slightly narrower, broadly rounded apices. Striae radiate throughout most of the valve, more widely spaced opposite the central area, convergent at the apices and characteristically bent where the orientation changes. Striae resolved as a series of lineate pores. Central area is rounded and expanded beside the central raphe endings. Central raphe endings slightly expanded, strongly hooked to one side at the poles. Live cells with two plate like chloroplasts along each side of the girdle. Two conspicuous droplets with characteristic caps lie towards the poles.
Navicula oppugnata Hustedt
Navicula rhynchotella Lange-Bertalot
Navicula slesvicensis Grunow in Van Heurck
Valves linear lanceolate, with broadly subrostrate, rounded apices, Striae slightly radiate through most of the vlave, to parallel or slightly convergent at the apices. The central striae on each side is slightly shorter, forming a somewhat rectangular central area. Pores clearly visible within the striae.
Navicula vaneei Lange-Bertalot in Witkowski et al.
