Landcare Research - Manaaki Whenua

Landcare-Research -Manaaki Whenua

Pleurosigma amarum S.R.Stidolph

Pleurosigma amarum

Type slide

Westshore, Napier, New Zealand; in salt marsh. Stidolph Collection BW-201/11.

Institution holding the type material


Known distribution

New Zealand; Kapiti Island: Okupe Lagoon, Lat. 40°50'S, Long. 174°56'E; Napier: Westshore, Lat. 39°28'S, Long. 176°52'E; Purimu Creek, Lat. 39°30'S, Long. 176°52'E; Miranda: Lat.  37°10'S, Long. 175°19'E.


Meaning "brackish of habitat".


Valve sigmoid, valve face flat up to about a quarter of distance from apex then vaulted towards narrowly rounded apices. Length of valve 253.6-360.0 µm, width 28.0-31.7 µm. Axial area narrow, central area small, conspicuous and orbicular; not rotated. Axial rib of single curvature, approximately central but displaced to convex valve margin near apices. Raphe angle +5/+7°. Helictoglossa conspicuous, terminal areas rather obscure, displaced slightly to concave side of axial rib. Striae transapical and oblique, crossing at 61-64°. Transapical and oblique striae 20-21 in 10 µm. Colour in standardised darkfield: peacock blue.


Funding from TFBIS (Terrestrial and Freshwater Biodiversity Information System), administered by the New Zealand Department of Conservation, is gratefully acknowledged.


Stidolph SR 1992. Observations and remarks on the morphology and taxonomy of the diatom genera Gyrosigma Hassall and Pleurosigma W. Smith III. Gyrosigma sterrenburgii sp. nov., and Pleurosigma amara sp. nov. Diatom Research 7: 345-366.