Hanicella moenia, gen. et sp. nov., a ribbon‐forming diatom (Bacillariophyta) with complex girdle bands, compared to Microtabella interrupta and Rhabdonema cf. adriaticum: implications for Striatellales, Rhabdonematales, and Grammatophoraceae, fam. nov.

Abstract

Tropical benthic diatoms are poorly known but constitute a rich resource for studies of diatom morphology and phylogeny. A remarkable tabellarioid ribbon-forming diatom with a very distinctive pattern of plastid distribution and unique valve and girdle band characters is described from Guam (Mariana Islands) as a new genus and species, Hanicella moenia. We were able to study the ultrastructure and ontogeny of the girdle bands, to compare several other genera in the Striatellales and the Rhabdonematales with numerous septate copulae and hyaline, nonseptate pleurae, and to evaluate their phylogenetic relationships. The last-formed two copulae of Microtabella interrupta have distended septa, the last interlocking with the other via a transverse ridge between two unique "ligules." The fourth pleura of Hanicella is a delicate, fimbriate band. Views of developing copulae of H. moenia indicated that the septum was formed by ingrowth from the sides rather than from the apex; this blurs the distinction between septate and scalariform valvocopulae. Phylogenetic results (i) confirmed that the Striatellales and Striatellaceae, consisting of Striatella and Pseudostriatella, are unrelated to clades containing Hyalosira, Microtabella, Hanicella, and Rhabdonema; and (ii) showed that the fRhabdonemataceae is close to, but separate from, the strongly supported Hanicella/Microtabella/Grammatophora clade, for which we propose Grammatophoraceae fam. nov. Formal genus and species descriptions of H. moenia are given and we also propose to restore Hyalosira interrupta to Microtabella with an emended genus description.

Indonesian coral reef habitats reveal exceptionally high species richness and biodiversity of diatom assemblages

“…It is evident that tropical littoral diatom assemblages are very rich in genera and species though they also show a very strong intraregional variability (Hendey, 1971;Montgomery, 1978;Frankovich et al, 2006;Gottschalk et al, 2007;Hein et al, 2008;Ashworth et al, 2012;Lobban et al, 2012;Lobban and Ashworth, 2014;Riaux-Gobin et al, 2015;Al-Handal et al, 2016;Lobban, 2018;Kryk et al, 2020, this study). To the best of our knowledge, the highest numbers of genera identified in coral reef habitats thus far amounted to 127 in Martinique and to >120 in Guam ( Desrosiers, 2014;Protistcentral.org), respectively.…”

“…Gottschalk et al, 2007;Hein et al, 2008;Lobban et al, 2012;Desrosiers, 2014;Al Handal et al, 2016;Kryk et al, 2020). Many species and genera have been described based on monoclonal strains and molecular markers have been acquired (Sato, 2008;Ashworth et al, 2012;MacGillivary & Kaczmarska 2012Lobban and Ashworth, 2014;Li et al 2016Li et al , 2018Dąbek et al 2017Dąbek et al , 2019Prasetiya et al, 2019;Witkowski et al, 2020).…”

Girdle Band Structure in the Diatom Genus Proschkinia (Bacillariophyta)—Another Potential Adaptation to Stabilise a Deep Cingulum?

“…Thus, although only a few genera with deep cingula have channelled, tubular or loculate copulae, others (e.g., Tabellaria Ehrenberg, Grammatophora Ehrenberg, Striatella C.A. Agardh, Pseudostriatella Sato et al, Hyalosira Kützing, Hanicella Lobban and Ashworth) have septa on one or more copulae [1,[21][22][23], which would also reduce the likelihood of cell distortion. These taxa usually form chains of some kind, straight or zig-zag, often attached to a substratum as well as to each other, and are thus susceptible to wave and water movement.…”

“…The numerous hollow copulae of Undatella have external advalvar and abvalvar flanges that overlap the adjacent [11] ( Figures 22,23 and 28), thereby linking the elements of the cingulum. Osada [18] ( Figures 18,19,22,23,25 and 26) provides more detailed micrographs of Undatella copulae, showing multiple rows of areolae on the inner side of the copulae and plain external surfaces. Short struts from the recurved advalvar margin on the outer surface link across to the pars interior to create the tubular form of the copulae [18] (Figures 17 and 18) but without closing them completely.…”

Ultrastructural and molecular characterization of diversity among small araphid diatoms all lacking rimoportulae. I. Five new genera, eight new species

“…Even recently, Cox () describes the group using the broadly defined characters of “cell elongate, often forming filaments held together by marginal spines. Apical pore fields and rimoportulae usually present.” Progress has been made in creating more sharply defined families from the Fragilariaceae; Lobban and Ashworth () separated the Grammatophoraceae based on molecular data and morphology, and Cox () removed nine genera from Fragilariaceae to Ulnariaceae, one genus to Rhaphoneidaceae, and three genera to Tabellariaceae, leaving 14 genera included in Fragilariaceae. Nevertheless, Fragilariaceae is still paraphyletic.…”