Éditeur(s) : HAL CCSD
Résumé : International audience
F.T. Kützing introduced Cocconeis molesta with only an uninformative description and a poor illustration: C. molesta has small, oblong valves and is an epiphyte. Another species, Cocconeis diaphana, described by William Smith, is said to have larger valves than C. molesta, with frustules that are relatively oblong. Smith described two forms: one with a distinct fascia on its raphe valve (var. β), the other without this feature. A third species, Cocconeis dirupta was described by Gregory, who expressed doubts that it differed from C. diaphana. Finally, Cocconeis molesta var. crucifera Grunow was first introduced in Van Heurck's Atlas but was subsequently treated by Van Heurck as a synonym of C. molesta. No previous account has examined the type material of these species. In this paper, we undertake that task and examine type slides and raw material in order to discriminate these different taxa. We conclude by recognizing three species: Cocconeis molesta Kütz., C. diaphana W.Sm. and C. dirupta W.Greg. Cocconeis diaphana var. β is considered to be a synonym of C. dirupta and C. molesta var. crucifera is considered to be a synonym of C. molesta. Lectotypes are designated for C. diaphana and C. dirupta.
ISSN: 2118-9773

Droits : http://creativecommons.org/licenses/by/
hal-01340453
https://hal-univ-perp.archives-ouvertes.fr/hal-01340453
https://hal-univ-perp.archives-ouvertes.fr/hal-01340453/document
https://hal-univ-perp.archives-ouvertes.fr/hal-01340453/file/329-1709-1-PB.pdf
DOI : 10.5852/ejt.2016.204

Éditeur(s) : HAL CCSD Czech Phycological Society
Résumé : International audience
As first observed on a group of taxa related to Cocconeis peltoides Hustedt, several other Cocconeis eHRenbeRG (Bacillariophyta) taxa possess a row of minute marginal pores on the external side of their sternum valve (SV) connected to small and simple internal portules, or processes. These processes are often located in continuity with the striae, but can also be slightly shifted or distant from the distal areola of the striae. The row of pores is often, but not always, externally separated from the stria by a crista marginalis. Within Cocconeis, and possibly all raphid diatoms, these processes seem unique and restricted to a few taxa. A list is presented of the taxa pertaining (or close) to Cocconeis that are actually known to share these micro–structures. In addition, the morphological variability of the processes is described in detail and a morphological comparison of the taxa is provided. The characteristic features of taxa showing a row of SV processes permit the tentative definition of several morphological groups. It is difficult to prove the taxonomic affiliation of these taxa and demonstrate or refute that these processes are ancestral characters. Some of these taxa are rare and restricted to low latitudes (e.g., tropical taxa) while others are frequent and ubiquitous. Abbreviations: (LM) light microscope, (SEM) scanning electron microscope, (RV) raphe valve, (SV) sternum valve, (RVVC) raphe valve valvocopula, (SVVC) sternum valve valvocopula
ISSN: 1802-5439

hal-01212883
https://hal-univ-perp.archives-ouvertes.fr/hal-01212883
https://hal-univ-perp.archives-ouvertes.fr/hal-01212883/document
https://hal-univ-perp.archives-ouvertes.fr/hal-01212883/file/fottea_fot-201502-0003.pdf
DOI : 10.5507/fot.2015.015

Éditeur(s) : HAL CCSD Magnolia Press
Résumé : International audience
A new species of the genus Cocconeis is described. Cocconeis sawensis sp. nov. was observed as epiphyte on the macrophyte Chara Linn. sp., collected from a saline lake in Iraq (Sawa Lake). Description of the new species is based on details observed with light and scanning electron microscopy. Cocconeis sawensis belongs to a group of taxa similar to Cocconeis euglypta Ehrenberg, but differs in a number of fine ultrastructural features including stria density and hymenes, raphe, valve shape and rim, valvocopula, hymen perforations and fimbriae shape as well as a presence of a pore-like structure reminiscent of a vestigial raphe in the sternum valve. A comparison with closely related taxa is given.
ISSN: 1179-3155

hal-01296895
https://hal-univ-perp.archives-ouvertes.fr/hal-01296895
DOI : 10.11646/phytotaxa.181.4.2

Éditeur(s) : HAL CCSD Magnolia Press
Résumé : International audience
Several diatoms in the family Achnanthaceae (Bacillariophyta), mainly from marine environments, have species with strongly apiculate, lemon-shaped valves. Some of them originally described under the genus Cocconeis (i.e., C. trachyderma or C. citronella), while others were first described as Stauroneis species [i.e. Stauroneis apiculata or S.(?) obesa]. Afterwards, Cocconeis citronella has been recombined within Achnanthes by Hustedt. The type material of C. citronella from Albert Mann’s collection, housed in the Smithsonian Institution (US), has been examined with light microscope; some ambiguities are pointed out and new details added to the original description. The intricate history of the latter taxon is redrawn and comparison with allied taxa are tentatively addressed. Cocconeis trachyderma is lectotypified and recombined as Achnanthes trachyderma comb. nov. Stauroneis apiculata and S.(?) obesa are recombined as Achnanthes apiculata comb. nov. and Achnanthes obesa comb. nov. respectively. The examination with light and scanning electron microscope of several marine samples from the Society Archipelago details the unique morphology of Achnanthes trachyderma which, until recently, has been often misidentified as Achnanthes citronella due to certain similarities between both taxa.
ISSN: 1179-3155

hal-01212892
https://hal-univ-perp.archives-ouvertes.fr/hal-01212892
DOI : 10.11646/phytotaxa.227.2.1