Chaetoceros mannaii, 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 : 33-34

Chaetoceros mannaii

Cells of C. mannaii are ultrastructurally similar to field material identified as C. lorenzianus from Thailand, Mexico and Japan ([ 12, 36], own observations). Compared to the original description of C. lorenzianus , C. mannaii has large poroids on the setae, 0.7±0.2 μm long, the largest among strains of section Dicladia examined by us, and readily visible in LM. They are more closely spaced (12.3±1.6) than in the type material of C. lorenzianus (7.2±1.7), and smaller than those of the Mexican ([ 12], pl. 23, figs 3 and 4) and Japanese material ([ 36], pl. VI, fig 7) tentatively identified as C. lorenzianus , where poroids of 1 μm or more were illustrated. In addition, the apertures of C. mannaii are hexagonal, compared to the more quadrangular apertures of C. lorenzianus (compare Figs 11C, 11d, 16A and 16B) [ 8]. Chaetoceros mannaii also differs in having a smaller apical axis, 5.7–12.9 μm, compared to 20–43 μm in C. lorenzianus [ 8], 13–25 μm in the Mexican material [ 12] and around 30 μm (with a variation of 10–

80 μm) in the Japanese material [ 36].

Cells of C. mannaii are otherwise characterized by heavily silicified frustules and a distinct furrow above the basal ring of the mantle ( Fig 11F, arrowheads). The terminal cell of C. mannaii carries a relatively long and distinct external tube of the rimoportula ( Figs 11E, 11F and 12C). An external tube was not observed in C. decipiens , C. laevisporus and C. mitra ( Figs 2F, 8E and 14G), and a very short one was present in C. elegans ( Fig 5D and 5E). This character still needs to be explored in C. lorenzianus .

Resting spores were not observed in C. mannaii although several attempts were made to induce spore formation.