Chaetoceros laevisporus, Li & Boonprakob & Gaonkar & Kooistra & Lange & Hernández-Becerril & Chen & Moestrup & Lundholm, 2017

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, PLoS ONE (e 0168887) 12 (1), pp. 1-38 : 34

Chaetoceros laevisporus

This is the only species in the C. lorenzianus complex with smooth resting spores without processes, and in the phylogenetic tree the strains form a separate branch. The smooth resting spore ( Fig 10A and 10B ) differs markedly from the spores of C. lorenzianus , C. mitra and C. elegans with their dichotomously-branching extensions. Furthermore the apertures are oval-peanut shaped in C. laevisporus ( Figs 8A, 8B, 8D and 10A ), thus differing from most other taxa in the complex. Seta poroid density is intermediate, 13.8± 1.9 in 10 μm as in C. mannaii ( Table 1 ), but different from all the other taxa. Poroid size on the setae was assessed to be c. 0.6 μm, slightly less than in C. mannaii , but the poroids were still visible in LM ( Fig 8C ).

Figures

Fig 8. Chaetoceros laevisporus sp. nov. LM (A–C), SEM (D and E) and TEM (F). Fig A: Part of a chain showing constrictions (arrows) between mantle and girdle, and V- shaped protrusion (arrowhead) located centrally on the terminal valve; strain N7. B: Dividing chain showing seta divergence; strain DY1. C: Structure of terminal seta; strain DY1. D: Chain in girdle view showing cells and apertures; strain N7. E: Terminal valve with rimoportula without external process (arrowhead); strain N7. F: Valve views of intercalary (upper) and terminal valves (below); strain N7. A, C, D scale bars,20 μm. B scale bar, 100 μm. E and F scale bars, 5 μm. doi:10.1371/journal.pone.0168887.g008

Fig 10. Resting spores of Chaetoceros laevisporus sp. nov. LM (A) and SEM (B). Resting spores within mother cells of a chain (A) and single, released resting spore (B); strain DY1. A scale bar, 20 μm. B scale bar, 5 μm. doi:10.1371/journal.pone.0168887.g010