Identification

Achnanthes brevipes C. Agardh has several ill-defined varieties including var. intermedia (Kützing) Cleve and var. angustata Grev.) Cleve. All show the usual Achnanthes bend in girdle view (geniculate). Chains of cells are joined by evident mucilage pads. The raphe valve has a stauros across the central nodule. Rapheless valve with a pseudoraphe displaced far to one side.
Vars. intermedia and angustata differ from the type variety in being somewhat smaller and narrower, with nearly parallel sides, and slightly higher stria density. The differences for var. intermedia are more strongly depicted in Hustedt/Jensen (1985) than in Witkowski et al. (2000) [the latter refer specimens to var. intermedia with a (?)], but neither of these works describe var. angustata.
Acid cleaned frustules from Guam shown here are coarsely punctate, 10-11 striae in 10 µm, and tentatively identified as var. angustata.

Plastids in our Palau specimens (not yet observed acid cleaned) were H-shaped plates in girdle view, with pyrenoids evident in girdle view and joining the opposite plates to give a 3D plastid that is also H-shaped in valve view. Hustedt, fig. 818b-c (citing Mereschkowsky), shows rectangular plates in the type species.

A. brevipes var. parvula (Kützing) Cleve has also been reported from the region, in an estuarine sample from Yap (Navarro & Lobban 2009).

References:
Type and intermedia: Hustedt/Jensen 1985, fig. 877; Witkowski et al. 2000, pl. 43: 1-5 vs. pl. 45: 1-12.
angustata: Foged 1987, p. IX: 9-13; Podzorski & Håkansson 1987, pl. 13: 4 (but not 5--which is evidently A. longipes!).

Projects This is Associated With

Western Pacific Diatoms Project

Last Updated

Added by Chris Lobban on May 15, 2009, 6:42 am
Last edited by Chris Lobban on May 15, 2009, 7:51 pm

Photos

Achnanthes brevipes	Achnanthes brevipes	Achnanthes brevipes	Achnanthes brevipes