Landcare Research - Manaaki Whenua

Landcare-Research -Manaaki Whenua

Thalassiosira hasleae U.V.Cassie & G.P.Dempsey

Thalassiosira hasleae

Type slide

Helensville Oxidation Pond 1, near Auckland, New Zealand. UVC Collection #40.

Institution holding the type material


Known distribution

Auckland: Helensville (36°40'S, 174°27'E); Orewa (36°35'S, 174°42'E); Waiuku (37°15'S, 174°44'E); Wesley College (37°09'S, 174°53'E).


After Dr Grethe R. Hasle, Department of Marine Biology and Limnology, University of Oslo, Norway, for contributions to the study of the genus.


Cells single or embedded in mucilage, not united by central threads, cylindrical, 8-20 µm in diameter, square to rectangular in girdle view, with bluntly rounded corners; pervalvar axis equal to or less than diameter of cell, mantle at a sloping angle to valve face; valves disciform; valve surface flat or concavo-convex; areolae hexagonal or circular, 24-36 in 10 µm near periphery of valve, radially or semi-linearly arranged, smaller and irregularly arranged near valve centre and valve mantle, loculate; foramina external; cribra internal; porelli 20-22 per cribrum, evenly spaced, not in straight lines, tubular; marginal strutted processes numerous, 27-44, 12-14 in 10 µm, in ring at junction between valve and valve mantle, arising every second or third areola; eccentric strutted processes 2-10, in clusters between centre and margin of valve; 1 or 2 labiate processes protruding externally from between two marginal strutted processes; valve mantle ribbed or areolate; areolae when present smaller than those on valve surface; epicingulum of regularly perforate valvocopulae and one or more pleurae; chloroplasts numerous, yellow-brown, irregularly discoid, lining periphery of cytoplasm; lamellae composed of three appressed thylakoids; electron-dense particles sometimes occurring between lamellae; usually a single membrane-bound pyrenoid with membranous structures traversing the matrix; nucleus with a single nucleolus, with up to 12 cisternae; mitochondria numerous, oval, with tubular cristae; lipid droplets, not membrane-bound, present in the cytoplasm.

Description reproduced with kind permission from Koeltz Scientific Books.


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


Cassie V, Dempsey GP 1980. A new freshwater species of Thalassiosira from some small oxidation ponds in New Zealand, and its ultrastructure. Baccilaria 3: 273-291.