Article

Revision of the genus Synedra Ehrenb

Diatom Research (Impact Factor: 1.75). 11/1986; 1(2):313-339. DOI: 10.1080/0269249X.1986.9704976

ABSTRACT

A large number of species originally assigned to Synedra have been investigated mainly by scanning electron microscopy. Most are marine or brackish in distribution and structurally they differ considerably from Synedra as defined from the freshwater species and hence we have been able to recognise five new generic taxa—Catacombas, Hyalosynedra, Tabularia, Ctenophora and Neosynedra. The characters used for their distinction are discussed.

    • "Despite comparative studies (e.g. Lange-Bertalot & Ulrich 2014) and major revisions (Williams & Round 1986, 1987, 1988) where several genera were proposed or established, the taxonomy of the group is still in a state of flux, as the systematic position of many species has been emended or transferred (e.g. Morales 2001, 2003, Edlund et al. 2006, Garcia 2006, Hamilton & Siver 2008). "
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    ABSTRACT: A new species of the genus Williamsella (Fragilariophyceae) is described from a saline lake in southern Iraq. Williamsella iraqiensis sp. nov. was found free living and as epiphyte on Chara sp. in Sawa Lake. This species is the second described of the genus Williamsella which was originally reported from Blue Lake warm springs, Utah, USA. Williamsella iraqiensis sp.nov. and W. angusta can be readily distinguished under LM by having a relatively wide sternum which results from shorter striae along valve margin. Description of valve ultrastructure and comparison with other related genera such as Fragilaria is provided. Williamsella iraqiensis is a brackish water species preferring warm waters.
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    • "The phylogenetic position of Neosynedra is unknown from DNA evidence , but it was left in Fragilariales : Fragilariaceae by Round et al . ( 1990 ) , along with the other Synedra derivatives of Williams & Round ( 1986 ) . Although plastids are useful generic characters in some cases ( e . "
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    ABSTRACT: Lucanicum concatenatum is a chain-forming araphid pennate, assigned to Cyclophorales: Cyclophoraceae on the basis of morphological characters and DNA sequences, resembling Neosynedra, but with platelike plastids and striae mostly undiv- ided by vimines. So far it has only been found growing on blue coral, Heliopora coerulea, but we do not suggest that it is restricted to this habitat. Its phylogenetic position, near Cyclophora, Florella and Astrosyne, requires amendment of the diag- nosis of Cyclophorales, which included characters unique to C. tenuis, the only species in the order at that time. The question of the scope and description of the Cyclophoraceae remains unresolved.
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    • "Although taxonomic treatments have become more discriminatory in the past few decades, taxonomy of the genus and its assumed relatives remains controversial (e. g. Williams and Round 1986, Krammer and Lange-Bertalot 1991). Despite these difficulties, it is apparent that one of the series present, if not identical to, is at least closely related to T. tabulata (C. A. Agardh) Snoeijs. "
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    ABSTRACT: Tabularia populations collected at a coastal site in Lake Erie, near Cleveland, Ohio, USA exhibit highly abnormal morphology. Frustules may be bent, asymmetric, have irregular striae patterns, irregular margins, or any combination of these characters. The majority of specimens in the collection are abnormal to some degree. Although specimens are so atypical that identification is difficult, relatively simple morphometric analysis shows that morphologies similar to most described members of the genus are present in the collection. Tabularia is probably not indigenous to the Laurentian Great Lakes but occurs in areas that have been highly modified, particularly by saline discharges. The collection site is subject to such discharges, and also to other industrial contaminants. The abnormalities present may be related to these factors, or simply to stresses imposed on species growing out of their preferred habitat. In any case, the occurrence of numerous forms of Tabularia in a localized area where it is not native is remarkable.
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