Two new marine species of Cocconeis (Bacillariophyceae) from the west coast of Sweden

This paper is part of a project of studying benthic diatom biodiversity on marine coastal regions of Sweden with focus on rare and less known species. Two new species of Cocconeis Ehrenb. are described from Vrångö, a small island in the west coast of Sweden. Both species were found as epiphytic on the green alga Ulva intestinalis L. Cocconeis magnoareolata Al-Handal, Riaux-Gob., R.Jahn & A.K.Wulff sp. nov. is a small species not exceeding 9 µm in length and characterized by having large subquadrangular areolae on the sternum valve. Cocconeis vrangoensis Al-Handal & Riaux-Gob. sp. nov. appears similar to some taxa of the ‘Cocconeis scutellum complex’, but differs by its stria density on both valves and variable features of the areola and valvocopula ultrastructure. Detailed descriptions based on light and electron microscopy examination, a comparison with closely related taxa, as well as a description of the habitat of both species are here presented

Distribution and morphology of the diatom genus Olifantiella Riaux-Gobin & Compère in Indonesian and Australian waters, including the description of O. gondwanensis sp. nov.

Samples from coastal tropical waters of Central Sulawesi, Bangka Island and Bawean Island in Indonesia and from the Great Barrier Reef at Fitzroy Island in Queensland, Australia were analysed for species composition of diatom assemblages with a focus on Olifantiella. Whereas samples from Fitzroy Island littoral in Australia retrieved only one species of Olifantiella, in Poso Bay, Indonesia, we observed at least six species. All established taxa were documented with light (LM) and scanning electron microscope (SEM) and principal component analysis (PCA) analysis was used to compare the species, based on the basic valve parameters of length, width, length to width ratio and striae density. A new species of the genus Olifantiella, O. gondwanensis is described from Australia. In addition, we showed the distinct nature of O. pilosella var. rhizophorae permitting to species status. Particular attention is placed on girdle bands in this genus

Two closely-related species of Cocconeis (Bacillariophyta): comparative study and typification

Background and aims – After its original description, Cocconeis grata A.W.F.Schmidt and Cocconeis pseudograta Hust. have been rarely quoted and illustrated. Due to the morphological resemblance between both taxa and because of their rare quotations, a certain degree of taxonomic confusion existed between both diatoms. In order to clarify the taxonomic history of these two taxa, we studied their type materials kept at the Hustedt Collection (Bremerhaven, Germany), and specimens of C. pseudograta recently collected in coastal waters of the Tahiti Island (Society Archipelago, southern tropical Pacific Ocean). Methods – Light and electron microscopy observations as well as morphometric data of frustules are presented, and an amended description for each taxon is provided. Key results – In addition to differences in stria and areola density, following frustule features allow to distinguish between both taxa: sternum valves (SV) areolae outline and occurrence of external depressions on the SV of C. grata and granules on the external valve face and marginal row of small processes on the SV mantle of C. pseudograta . Conclusions – Based on the frustule morphology and morphometric data, we conclude that C. grata and C. pseudograta are independent species. While the former can still be considered 'American' in its distribution, the occurrence of C. pseudograta in coastal waters of the Tahiti Island invalids its previous designation as 'European form'

Two closely-related species of Cocconeis (Bacillariophyta): comparative study and typification

Background and aims – After its original description, Cocconeis grata A.W.F.Schmidt and Cocconeis pseudograta Hust. have been rarely quoted and illustrated. Due to the morphological resemblance between both taxa and because of their rare quotations, a certain degree of taxonomic confusion existed between both diatoms. In order to clarify the taxonomic history of these two taxa, we studied their type materials kept at the Hustedt Collection (Bremerhaven, Germany), and specimens of C. pseudograta recently collected in coastal waters of the Tahiti Island (Society Archipelago, southern tropical Pacific Ocean). Methods – Light and electron microscopy observations as well as morphometric data of frustules are presented, and an amended description for each taxon is provided. Key results – In addition to differences in stria and areola density, following frustule features allow to distinguish between both taxa: sternum valves (SV) areolae outline and occurrence of external depressions on the SV of C. grata and granules on the external valve face and marginal row of small processes on the SV mantle of C. pseudograta . Conclusions – Based on the frustule morphology and morphometric data, we conclude that C. grata and C. pseudograta are independent species. While the former can still be considered 'American' in its distribution, the occurrence of C. pseudograta in coastal waters of the Tahiti Island invalids its previous designation as 'European form'

Coccolithophorids from the Marquesas Islands and atolls in the Tuamotu and Society Archipelagos (South Pacific Ocean)

International audienceCoccospheres and loose coccoliths were found on solid substrates (intertidal sediments and macroalgae) collected from the Marquesas Islands and atolls in the Tuamotu and Society Archipelagos, South Pacific Ocean. Visual observations suggest that the species diversity (11 taxa) and abundances were both low; however, the presence of Braarudosphaera bigelowii, Cruciplacolithus neohelis and Gephyrocapsa oceanica coccospheres provided evidence of a coastal assemblage. The association among the two species, B. bigelowii and C. neohelis, and living oyster shells was unusual, given that B. bigelowii is normally found in the plankton and C. neohelis on sand or coral fragments

An account of Astartiella species from tropical areas with a description of A. societatis sp. nov. and Nomenclatural notes

During a survey of the diatom community associated with coral reefs at Tahiti Island, Society Archipelago, South Pacific, two species belonging to Astartiella Witkowski, Lange-Bertalot & Metzeltin, including A. societatis Riaux-Gobin, Witkowski & Romero sp. nov. a species morphologically similar to A. bremeyeri (Lange-Bertalot) Witkowski & Lange-Bertalot, were found from the teguments of a large Holothuria atra Jaeger (Echinodermata). The second species, A. punctifera (Hustedt) Witkowski & Lange-Bertalot, occurred on nearby marine sediments. These species were compared with other Astartiella taxa recorded at similar latitudes in the Indian Ocean, namely Juan de Nova, Scattered Islands and Mascarene Archipelago. Nomenclatural issues along with the proposed transfer of Achnanthes heterostriata Hustedt to Astartiella are discussed. © 2013 The International Society for Diatom Research.Peer Reviewe

Achnanthes citronella, A. trachyderma comb. nov. (Bacillariophyta) and allied taxa pertaining to the same morphological group

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

Cocconeis nosybetiana sp. nov. from Nosy Be Island (Madagascar) and allied taxa

International audienceCocconeis nosybetiana sp. nov. is described from Nosy Be Island (Madagascar, IndianOcean). This taxon is characterized by its sternum valve (SV) with ‘diabolo-like’ areolae (hymenes/supported by two transapical pegs), by its round valve shape and its raphe valve valvocopula(RVVC) with irregular short fimbriae and simple papillae. The raphe valve (RV) of the new taxonshares many similarities with that of Cocconeis scutellum Ehrenberg, except for its RVVC. Com-parison of the new species with allied taxa, particularly C. scutellum var. posidoniae f. decussata,is provided. In this case, the two taxa mainly differ in the structure of the SV areolae, which havean apical complete bar in place of transapical short pegs in C. nosybetiana. Furthermore, the shapeof the valve, the RV stria density, as well as the fimbriae and papillae of the RVVC are differentbetween the two latter taxa. The role of recent EM technologies on the morphological discrimina-tion of close taxa is discussed