Melosira dickiei

(Thwaites) Kütz. 1849      Category: Centric
BASIONYM: Orthoseira dickiei Thwaites 1848

Mastogloia pumila


Melosira normannii

LM scalebar = 10 µm = 40 pixels.


Contributor: Mark Edlund | David R.L. Burge - July 2017
Diameter: 9.6-20.1 µm
Mantle Height: 4.5-6.0 µm
Rows of areolae in 10 µm:


Frustules are loosely joined in short filaments of 1-4 cells. The length of the pervalvar axis of each frustule is 10.2-13.0 µm. Valves are cylindrical with a flat face. The mantle is narrow, and because of that, isolated valves most often lie in valve view. The valve surface is finely punctate and areolae are not obviously arranged. In some specimens, the valve face has short spinules, that may aid in filament formation. Multi-walled endogenous resting spores of various sizes and curvature are common.

Material collected in Europe is reported to have greater mantle height (7-10 µm) (Houk 2003) .

Original Description

Basionym: Orthoseira dickiei
Author: Thwaites 1848
Diameter: µm
Rows of areolae in 10 µm:

Original Description

Orthoseira Dickieii, n. sp. Pl. XII. fig. E 1-7 (220/1). Filamentis brevibus ; cellulis laevissimis. The filaments of this beautiful species consist generally each of from two to four frustules, which are hyaline and perfectly smooth, and each with its central cavity filled with a dark red-brown endochrome. The sporangium of Orthoseira Dickieii is no less beautiful than interesting : it is fusiform in shape and marked with numerous annular constrictions, each with a corresponding internal septum or chamber, the origin of which can only be understood by paying attention to the early development of the sporangium. In fig. E3 is shown a filament of this species, the terminal cells of which have each commenced to develop a sporangium ; E4 represents two such cells or young sporangia ; and E5 a mature sporangium. It will be observed that the formation of the ring-like markings is progressive, and that they go on increasing in number until the sporangium is fully developed. At the commencement of the formation of the sporangium, the endochrome, at the same time that it withdraws from the end of the frustule, produces at its centre an additional ring of cell-membrane ; and this process continuing to take place at certain intervals—each new ring of cell-membrane exceeding in diameter those previously formed—produces at length the structure represented in E5. Or it may be a more correct explanation of the process to say, that an entire new cell-membrane has been developed by the young sporangium at the time each new ring has been formed, and that thus have originated the several chambers into which the ends of the sporangium are divided. Fissiparous division of the sporangium subsequently takes place, as shown in fig. E6, and sporangial frustules are developed from each half, E7.

Original Images

Cite This Page:
Edlund, M., and Burge, D. (2017). Melosira dickiei. In Diatoms of the United States. Retrieved April 21, 2018, from

Species: Melosira dickiei

Contributor: Mark Edlund | David R.L. Burge

Reviewer: Sarah Spaulding


Houk, V. (2003). Atlas of Freshwater Centric Diatoms with a Brief Key and Descriptions. Part I. Melosiraceae, Orthoseiraceae, Paraliaceae and Aulacoseiraceae. Czech Phycology Supplement, Volume 1, Czech Phycological Society, Olomouc.

Johansen, J.R., Lowe, R.L., Carty, S., Fuciková, K., Olsen, C.E., Fitzpatrick, M.H., J.A. Ress, J.A. and Furey, P.C. (2007). New algal species records for the Great Smoky Mountains National Park, with an annotated checklist of all reported taxa from the park. Southeastern Naturalist, Special Issue 1: 99-134.

Kützing, F.T. (1849). Species Algarum. Lipsiae. F.A. Brockhaus, 922 pp.

Thwaites, G.H.K. (1848). Further observations on the Diatomaceae with descriptions of new genera and species. Annals and Magazine of Natural History, 2nd series, 1: 161-172, pl. 11, 12.

Links & ID's

Index Nominum Algarum (INA)

Transfer INA
Original INA

California Academy of Sciences (CAS)

Melosira dickiei CAS

North American Diatom Ecological Database (NADED)


Autecology Discussion

This taxon is aerophilic, uncommon but found on wet walls and in the entries to caves. Material presented in images here was collected from Mammoth Cave, Kentucky. Melosira dickiei has also been reported from the Great Smoky Mountains National Park (Johansen et al. 2007).


Multi-walled endogenous resting spores, two levels of focus. Mammoth Cave National Park, Kentucky Wet wall scrape, Coll: T.E. Smith, 24Aug199. Scale bar = 10 µm.

Credit/Source: M.B. Edlund

Isotype material from Scotland (Grampian) Aberdeen, HLSmith exsiccata 222 (MBEdlund collection, Science Museum of Minnesota)

Credit/Source: M.B. Edlund

Auxospore produced by Melosira dickiei. MBE 1076B, Science Museum of Minnesota. Mammoth Cave National Park, Kentucky. Scale bar = 10 µm.

Credit/Source: M.B. Edlund