Holotype species: Melosira crenulata (Ehrenberg) Kützing
Currently accepted name for the type species: Aulacoseira crenulata (Ehrenberg) Thwaites
Original publication and holotype designation: Thwaites, G.H.K. (1848). Further observations on the Diatomaceae with descriptions of new genera and species. Annals and Magazine of Natural History, Series 2 1: 161-172, pls XI, XII.
Taxonomic status: currently recognized as a distinct genus.
Most recent taxonomic treatment adopted: Stoermer, E.F. & Julius, M.L. (2003). Centric Diatoms. In: Freshwater Algae of North America. (Wehr, J.D. & Sheath, R.G. Eds), pp. 559-594. San Diego: Academic Press.
Centrales, Bacillariophyceae (McCausland et al. 2002) - (13 Aug 2009) - Wendy Guiry
Description: Cells linked tightly to form long straight, curved or even coiled filaments. Plastids discoid. A common freshwater, planktonic genus previously placed in Melosira. Valves circular. Valve face plain or with scattered poroids, which are often restricted to its periphery. Valve mantle deep, making a right angle to the planar valve face from which it is sharply differentiated; with vertical or curved rows of areolae. Mantle edge plain. Valve face/mantle junction provided with spines, which are expanded at their apices and fit with the spines of adjacent cells to form a linkage breakable only by damaging the spines. In some species the spines have two 'roots' that straddle a row of pores on the mantle, others have a single 'root' that runs between pore rows. Separation cells occur at intervals in A. granulata, the spines on these being lanceolate and of variable length; the areolae of separation valves are often in straight rows, those on other valves spiralling away from the sibling junction in opposite directions. Inside the valve mantle, at the junction between the plain mantle edge and the areolate portion, there is a thickening (ringleiste), which is hollow in A. ambigua. Mantle areolae simple, round to rectangular, containing volate occlusions. Small rimoportulae occur inward of the ringleiste and open through it to the outside. The copulae are split rings with ligulae; they are finely areolate, with an advalvar pars media.The most recent alteration to this page was made on 21 Nov 2017 by M.D. Guiry.
Comments: Simonsen (1979) resurrected the long disused name Aulacosira (sic) and the common species italica, granulata, islandica, nyassensis and distans of the genus Melosira are placed here (see also Haworth, 1988). M. varians has a very different wall structure and remains in Melosira (see p. 154). Davey & Crawford (1986) showed that the frequency of separation valve formation in A. granulata controls filament length, which in turn (Davey, 1986, 1987) may influence the buoyancy of this diatom. Why some species, e.g. A. italica subsp. subarctica, only appear to have separation valves while others, e.g. A. ambigua, only have linking valves is unexplained.
Numbers of names and species: There are 139 species names in the database at present, as well as 65 infraspecific names. Of the species names, 118 have been flagged as accepted taxonomically on the basis of the listed literature under the species name. In some instances, opinions on taxonomic validity differ from author to author and users are encouraged to form their own opinion. AlgaeBase is a work in progress and should not be regarded as a definitive source only as a guide to the literature..
Names: ('C' indicates a name that is accepted taxonomically; 'S' a homotypic or heterotypic synonym; 'U' indicates a name of uncertain taxonomic status, but which has been subjected to some verification nomenclaturally; 'P' indicates a preliminary AlgaeBase entry that has not been subjected to any kind of verification. For more information on a species click on it to activate a link to the Species database):
Click here to also show infraspecific names in the list below.
Verification of data
Users are responsible for verifying the accuracy of information before use, as noted on the website Content page.
Some of the descriptions included in AlgaeBase were originally from the unpublished Encyclopedia of Algal Genera, organised in the 1990s by Dr Bruce Parker on behalf of the Phycological Society of America (PSA) and intended to be published in CD format. These AlgaeBase descriptions are now being continually updated, and each current contributor is identified above. The PSA and AlgaeBase warmly acknowledge the generosity of all past and present contributors and particularly the work of Dr Parker.
Descriptions of chrysophyte genera were subsequently published in J. Kristiansen & H.R. Preisig (eds.). 2001. Encyclopedia of Chrysophyte Genera. Bibliotheca Phycologica 110: 1-260.
Created: 11 April 2002 by M.D. Guiry
Verified by: 08 February 2014 by M.D. Guiry
Linking to this page: http://www.algaebase.org/search/genus/detail/?genus_id=43675
Please cite this record as:
M.D. Guiry in Guiry, M.D. & Guiry, G.M. 2019. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. http://www.algaebase.org; searched on 20 August 2019.