(Grunow) Hasle 1977 Category: Centric
BASIONYM: Coscinodiscus lacustris Grunow in Cleve & Grunow 1880
SYNONYM(S): Cyclotella punctata W. Smith 1856 | Stephanodiscus punctatus (W. Smith) Grunow 1878
REPORTED AS: Thalassiosira bramaputra ((Ehrenberg) Håkansson and Locker 1981)
Contributor: Pat Kociolek - March 2011
Length Range: 13-32 µm
Striae in 10 µm:
Valves are rounded and tangentially undulate on the valve face. Areolae are rectangular to irregular in shape and organized into radial rows of coarse striae that may appear slightly disorganized. A ring of marginal fultoportulae is present. These fultoportulae have external tubes, giving the impression of a ring of short spines around the valve periphery. A prominent rimoportula is present on the valve face, close to the margin.
This taxon has been misidentified as T. bramaputra, which has not been verified in North America. According to Smucker et al. (2008), Thalassiosira bramaputrae has two marginal rings of evenly spaced fultoportulae. In contrast, T. lacustris has one complete ring of marginal fultoportulae and an inner ring of irregularly spaced occluded processes. The inner ring of proccesses number about half the number of marginal fultoportulae.
Basionym: Coscinodiscus lacustris
Author: Grunow in Cleve & Grunow 1880
Length Range: µm
Striae in 10 µm:
Germain, H. (1981). Flore des diatomées - Diatomophycées- eaux douces et saumâtres du Massif Armoricain et des contrées voisines d’Europe occidentale. Collection "Faunes et Flores Actuelles". Société Nouvelle des Editions Boubée, Paris. 444 pp.
Hasle, G.R. and Fryxell, G.A. (1977). The genus Thalassiosira: some species with a linear areola array. In: R. Simonsen (ed.), Proceedings of the Fourth Symposium on Recent and Fossil Marine Diatoms, Oslo, 1976. Beihefte zur Nova Hedwigia 54:15-66.
Hasle, G.R. and Lange, C.R. (1989). Freshwater and brackish water Thalassiosira (Bacillariophyceae): taxa with tangentially undulated valves. Phycologia 28:120-135.
Smucker, N.J., Edlund, M.B. and Vis, M.L. (2008). The distribution, morphology and ecology of a non-native species, Thalassiosira lacustris (Bacillariophyceae), from benthic stream habitats in North America. Nova Hedwigia 87: 201-220.