Research Article |
Corresponding author: Bart Van de Vijver ( bart.vandevijver@meisebotanicgarden.be ) Corresponding author: Rémy Chavaux ( remy.chavaux@ofb.gouv.fr ) Academic editor: Kalina Manoylov
© 2024 Bart Van de Vijver, Margaux Pottiez, Rémy Chavaux.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Van de Vijver B, Pottiez M, Chavaux R (2024) Gomphonema vancampianum sp. nov. (Gomphonemataceae, Bacillariophyceae), a new large Gomphonema species from Europe. PhytoKeys 244: 1-13. https://doi.org/10.3897/phytokeys.244.122153
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During a French biomonitoring survey of the lakes in the region Rhône-Méditerranée-Corse, a large, unknown Gomphonema taxon was observed in a lake in the vicinity of the City of Lyon (Département du Rhône, France), that could not be identified using the currently available literature. Detailed light and scanning electron microscopy investigations revealed the presence of two types of valves, one bearing a thick marginal crest and valves lacking the crest. Following comparison with similar, mostly tropical Gomphonema species, the unknown taxon is described as new: Gomphonema vancampianum sp. nov. Discriminating features of the new species include the peculiar valve shape resembling a Chinese spoon, the broad upper valve part with acuminate tip, the presence of shallow depressions in the axial area, distinctly punctate striae and the occasional presence of the marginal crest. The new species was observed in several samples collected in an oligo- to mesotrophic, calcium-carbonate rich lake with a high ecological quality.
Europe, France, Gomphonema, morphology, new species
The genus Gomphonema is one of the dominant freshwater genera in European rivers and lakes (
During a French biomonitoring survey of the lakes in the region Rhône-Méditerranée-Corse (southern France), several populations of a large, unusual Gomphonema taxon were observed in samples collected from the artificial Lac du Drapeau (“Flag lake”) located in the vicinity of the French City of Lyon (Dépt. du Rhône, France). The largest populations seemed to be associated with submerged helophytes and aquatic plants. Despite a detailed morphological analysis, comparing the unknown taxon with all similar larger Gomphonema species worldwide, the taxon could not be identified. This contribution describes in detail the morphology of the new species highlighting its remarkable level of variability. Its morphology is compared with known species from the Gomphonema apiculatum
Lac du Drapeau (elev. 170 m) is a 61 ha large lake of a calcium-carbonate sedimentary nature with a maximum depth of 3.2 m. The Lake was created following the extraction of materials in the Rhône plain and is fed by the aquifer of the Island of Miribel-Jonage and the Rizan Stream and finally flows into the Eaux Bleues gravel pit. Although the surrounding area experiences some anthropogenic (mainly recreational) pressure, the Lac du Drapeau is closed to the public as it is used for flood control and serves as a drinking water reservoir for the City of Lyon (Agence
Six samples were collected from three different localities in the Lake. At each locality, one sample was gathered by scraping off five submerged stones, while a second sample was collected by squeezing five aquatic plants, keeping the water in small plastic vials. All samples were immediately fixed with ethanol on site.
All samples were prepared for LM and SEM observations following the method described in
Terminology used in the description of the various structures of the siliceous cell wall is based on
For typification of the species, we chose to use the entire slide as the type, following article 8.2 of the International Code for Botanical Nomenclature (
Holotype. BR-4839 (Meise Botanic Garden, Belgium). Fig.
Gomphonema vancampianum sp. nov. LM micrographs taken from the holotype material (BR-4839, Lac du Drapeau, Sample DRAPEAU-U03VEG, France) A LM picture of a frustule in girdle view. The arrow indicates the smaller, more distantly spaced areolae on the mantle B–O LM pictures of valves in valve face view in decreasing length. The arrows indicate the possible presence of the marginal crest. Scale bar: 10 µm.
Lac du Drapeau (Lyon, Département du Rhône, France), sample Drapeau-U03-VEG, (coll. date 22.viii.2023, leg. R. Chavaux).
This species is named in honour of Prof. Dr Karel Van Camp, former Physics professor of the first author at Antwerp University (Belgium) and life-long enthusiastic amateur diatomist and microscopist.
LM
(Fig.
Gomphonema vancampianum sp. nov. SEM micrographs taken from the holotype material (BR-4839, Lac du Drapeau, Sample DRAPEAU-U03VEG, France) A SEM external view of the headpole in girdle view showing the marginal crest on both valves, the larger, reniformly occluded upper areolae and the smaller, more distant areolae towards the mantle edge. Note also the slit-like pores on the girdle band B SEM external detail of the upper valve part of a valve bearing a crest showing the lowering marginal crest at the apex C SEM external view of an entire crest-bearing valve. Note the shallow depressions in the axial area D SEM external view of valve without marginal crest. Note the shallow depressions in the axial area and the valve face striae continuing over the valve face/mantle junction E SEM external detail of the central area with the depressed large areolae and the stigmoid. The shallow pit-like depressions are well visible in the axial area F SEM external detail of the footpole with the distal raphe fissure bisecting the apical pore field. Scale bars: 10 µm (A–D), 5 µm (E–F).
Gomphonema vancampianum has so far only been found in several samples from the type locality in France. The largest population was found in a sample collected from submerged aquatic plants. The diatom flora is dominated by species typically found in calcium-carbonate rich, oligotrophic lakes with low nutrient concentrations and low saprobity. The sample is dominated by several cymbelloid taxa (e.g. Encyonopsis subminuta Krammer & E.Reichardt, Cymbella affiniformis Krammer, C. lange-bertalotii Krammer, Cymbopleura amphicephala (Nägeli) Krammer) together with a, so far, unidentified, long-celled Fragilaria species, Brachysira neoexilis Lange-Bertalot, B. cf. chiaruccii Cantonati et al. and Nitzschia cf. subacicularis Hustedt, all indicating the environmental conditions mentioned above (
Gomphonema vancampianum sp. nov. SEM micrographs taken from the holotype material (BR-4839, Lac du Drapeau, Sample DRAPEAU-U03VEG, France) A SEM internal view of an entire valve B SEM internal detail of the central area with the stigmoid located in a long depression, the hooked central raphe endings and the long foramina with the areolae C SEM internal detail of the areolae with the small silica struts D SEM internal detail of the footpole with the small pseudoseptum, the helictoglossa and the apical pore field E SEM external view of an entire valve with marginal crest from Lac du Réaltor, Provence, France (photo courtesy of Dr Carlos E. Wetzel). Scale bars: 10 µm (A, E), 1 µm (B–D).
Despite its rather large valve dimensions, its conspicuous form and structure, Gomphonema vancampianum could not be identified using all currently available literature. In the editorial note to
Although similar in some respect (valve length, stria density, areolae discernible in LM), the North-American population, (erroneously) identified by
Gomphonema vancampianum also shows some resemblance to a group of tropical species related to G. apiculatum Ehrenberg.
A final species showing some resemblance is Gomphonema turris Ehrenberg, described in 1843 from North America. The taxonomic history of the species had been analysed by
Mrs Myriam de Haan (Meise Botanic Garden, Belgium) is thanked for her help with the SEM analysis. Mr. Wolf-Henning Kusber (Botanic Garden Berlin-Dahlem) is thanked for his taxonomic advice regarding G. apicatum. We are grateful to Dr Ingrid Jüttner, Dr Loren Bahls and Dr Carlos E. Wetzel as well as the editor, Dr Kalina Manoylov, who provided insightful comments that significantly contributed to enhancing the content of this manuscript. Dr Wetzel is thanked for the picture of G. vancampianum from Lac du Réaltor (France).
The authors have declared that no competing interests exist.
No ethical statement was reported.
This research received support from Office Français de la Biodiversité (OFB grant CP C5411 Diatomées Plans d’eau: determination).
Bart Van de Vijver: specimen analysis, original draft, writing, editing, Margaux Pottiez: specimen analysis, editing, Rémy Chavaux: sampling, sample analysis, editing.
Bart Van de Vijver https://orcid.org/0000-0002-6244-1886
Margaux Pottiez https://orcid.org/0009-0009-2282-8355
All of the data that support the findings of this study are available in the main text.