valve view brightfield	valve view brightfield
	valve view brightfield
SEM	live brightfield
live brightfield with epiphytic bacteria

Description
Cells solitary. Frustules heteropolar in valve and girdle view, bilaterally symmetrical. Cells lie in valve or girdle view and isolated valves always in valve view. Valves bilaterally symmetrical, heteropolar, oval, with the broader pole smoothly rounded but the narrower pole slightly pointed, becoming almost circular in the smallest specimens. Transverse striae visible, somewhat irregular, interrupted along the midline of the valve by a narrow, linear or irregular, hyaline area. The valve face is slightly folded at the inner margins of the fibulae, differentiating central and marginal zones. Raphe system fibulate (the raphe itself is impossible to detect in LM), marginal, occupying the whole perimeter of the valve. Some fibulae rib-like, tapering, extending in from the margin by approximately a fifth of the (maximum) valve width. Those fibulae that are aren't extended inwards are tiny bars difficult to detect in LM. There is one chloroplast per cell, consisting of two large plates, often lobed at their margins, connected by a narrow isthmus that lies near one end of the cell. The plates lie against the valves and, when seen in valve view, appear to fill all except the cell periphery.

Character	State
If elliptic or elongate, length	(8)-8-70-(70) µm
If elliptic or elongate, width	(8)-8-30-(30) µm
If striae resolvable, density	(16)-17-19-(20) /10µm
If fibulae, density	(3.5)-3.5-6-(7) /10µm
Shape in valve view	Elliptical or elongated
If elliptic or elongate, transapical symmetry	Heteropolar
	Isopolar
If elliptic or elongate, apical symmetry	Isobilateral
Raphe	Present
	Absent
If raphe, position	Around both sides of valve
If raphe, fibulae	Entire perimeter of vale
	Absent

Habit

Character	State
Colonies	Solitary cells
Attachment	Not attached (floating or freely motile)
Motile?	Yes

True	Rarely True	Unknown
Only by Misinterpretation

Don't confuse with:

Surirella brightwellii

the very much more folded valve face of S. brightwellii, creating a marginal zone with fibulae (one-fifth of the maximum width), a central elliptical or lanceolate zone (over a third of the width), and a narrow depressed zone between them. In addition, subcircular and broadly elliptical valves of S. brightwellii are much larger than similarly shaped S. brebissonii valves (18-28 as against c. 12-16 µm)

Surirella crumena

the more circular/elliptical shape of S. crumena; the smallest valves of S. brebissonii can have similar shape to S. crumena but they are then much smaller than their S. crumena equivalents (much less than 20 µm, compared to > 27 µm)

Surirella minuta

the more linear shape, smaller size and more closely spaced fibulae of S. minuta.

Surirella ovalis

the slightly pointed wider pole of S. ovalis; in S. brebissonii the wider pole is smoothly rounded.

Surirella patella

the generally larger size of S. patella (mostly > 20 µm width) and lower fibula density (generally < 3.5 in 10 µm); also, the position of the broadest point of the valve is generally nearer the broad pole in S. patella (c. 70% from the base) than in S. brebissonii (50-60% from the base)

Taxonomic Comment
This group of Surirella species has a confusing taxonomic history. For much of the 20th century, S. brebissonii specimens would have been identified as S. ovata Kützing. However, according to Krammer & Lange-Bertalot (1987: see also Lange-Bertalot & Krammer, 1987), no type material is available for S. ovata and Kützing's protologue is ambiguous. They therefore described a new species, S. brebissonii. However, this leaves S. ovata as an unassigned but unrejected name. There seems no reason why it should not have been applied to the taxon now called S. brebissonii, especially given the long use of 'S. ovata' for this diatom.

Related Taxa
Surirella brebissonii, S. minuta, S. ovalis, S. brightwellii, S. patella and some other species form a group within Surirella characterized by broad heteropolar valves, extended, rib-like fibulae, and the presence of closely spaced striae extending in from the raphe to the midline

Ecological Information
Epipelic in fresh and brackish waters

Water quality indicators: