Three new species of Fallacia from intertidal sediments in Japan

Abstract

Three new species of Fallacia, F. miyajimensis sp. nov., F. nodulifera sp. nov., and F. similigemmifera sp. nov. are described from intertidal sediments in Japan. Their morphologies are studied with light, scanning and transmission electron microscopy. Fallacia miyajimensis differs from congeners in the presence of an apical pore, a finely porous conopeum possessing finger-shaped extensions with uniseriate rows of pores and a thick layer adjacent to the raphe with isolated depressions with small pores inside. Fallacia nodulifera differs from congeners in the presence of a unique asymmetric internal central nodule. It can also be distinguished by the combination of stria density, conopeum with short extensions, and centrally convex lateral sterna. Fallacia similigemmifera differs from congeners by its lanceolate valve outline, more or less straight, distinct lateral areas and the presence of a rectelevatum on internal central nodule. We suggest that the structural combination of the structure of the conopeum and the lateral sterna is a stable feature in species discrimination and could be used to define species groups. The cingulum of F. similigemmifera comprises a wide open valvocopula and two linear bands with different ligulae. This type of cingulum structure is also present in F. tenera, F. hodgeana, and probably in F. litoricola and F. fracta as well, and likely occurs commonly in Fallacia.

Keywords:

• benthic diatoms
• Fallacia
• intertidal sediments
• new species
• Japan

Acknowledgements

The authors appreciate two anonymous reviewers, Prof. Koen Sabbe and Dr E.J. Cox for their constructive comments and suggestions and kind efforts in refining the paper.

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Yuhang Li http://orcid.org/0000-0002-5546-1774

Additional information

Funding

This work has been supported by Grants-in-Aid for Scientific Research [C: 16K07838 and B: 16H04960] from the Japan Society for the Promotion of Science, and the National Natural Science Foundation of China [No. 31800171].