Dicladia
Creators: name: Li, Yang
name: Boonprakob, Atchaneey
name: Gaonkar, Chetan C.
name: Kooistra, Wiebe H. C. F.
name: Lange, Carina B.
name: Hernández-Becerril, David
name: Chen, Zuoyi
name: Moestrup, Øjvind
name: Lundholm, Nina
Publisher: name: Zenodo
Year: 2017
Subjects: Biodiversity
Taxonomy
Chromista
Ochrophyta
Bacillariophyceae
Dicladia

description: Additional morphological characters in section Dicladia?
A feature of C. laevisporus which occurs also in C. decipiens and C. elegans (Figs 1G and 4D, arrowheads) is the presence of a non-silicified, V-shaped protrusion on the terminal valves (Fig 8A, arrowhead). Chaetoceros cf. lorenzianus from the Gulf of Panama shows the same feature [35]. This, together with the reduced external tube of rimoportula on the terminal valve (loc. cit. figs 77–80 in [35]) clearly places this material as belonging to C. laevisporus, The Vstructure was observed in C. decipiens by Rines & Hargraves [10] and Jensen & Moestrup [9], and may be present in more species of the section. Because of its non-silicified nature, the structure disappears in acid-cleaned material.
The ear-like structures at the marginal border of the apertures have been observed in all the studied strains, often in different shapes on the intercalary valves and terminal valves. In C. decipiens and C. mitra, the structures are very distinct, and they interconnect the edges of sibling valves on each side of the aperture (Figs 3B, 3C and 14F). In C. elegans, C. laevisporus and C. mannaii they are smaller, sometimes with overlapping parts (Figs 6A, 6B, 9A, 9B, 11C and 11D). On the terminal valves, these structures vary in shape, as fringes in C. decipiens, C. laevisporus and C. mitra (Figs 2F, 9C and 14G) and as slice-shaped structures in C. elegans and C. mannaii (Figs 5D and 11E). Based on the morphological variation observed, and the potential influence of environmental factors on the development of the structures, it is somewhat uncertain whether they can be used as a species-specific character.
Although our study was based on established strains, with the risk of culture condition artefacts affecting the morphology, we regard the present species delineation sound, due to the following: 1) strains were fixed soon after establishment and morphology is thus not very likely affected by artefacts, 2) several of the species are based on strains from separate locations showing the same morphology, 3) observations of field samples made it possible for us to identify the taxa based on the descriptions provided, 4) evaluations with previously published records of species belonging to Dicladia, for which electron micrographs are available (S3 Table) support our observations and 5) the study was performed over a long period, and subsequently established strains confirmed the species descriptions.
description: Published as part of Li, Yang, Boonprakob, Atchaneey, Gaonkar, Chetan C., Kooistra, Wiebe H. C. F., Lange, Carina B., Hernández-Becerril, David, Chen, Zuoyi, Moestrup, Øjvind & Lundholm, Nina, 2017, Diversity in the Globally Distributed Diatom Genus Chaetoceros (Bacillariophyceae): Three New Species from Warm-Temperate Waters, pp. 1-38 in PLoS ONE (e 0168887) (e 0168887) 12 (1) on pages 34-35, DOI: 10.1371/journal.pone.0168887, http://zenodo.org/record/12827437