Entomoneis annagodhei sp. nov., a new marine diatom (Entomoneidaceae, Bacillariophyta) from the west coast of Sweden

The genus Entomoneis includes diatoms with an elevated bilobate keel, a sigmoid raphe canal and numerous girdle bands. It is known to inhabit various environments, from freshwater to marine, both plankton and benthos. During a phytoplankton investigation in the Kungälv estuary on the west coast of Sweden, we observed numerous cells belonging to Entomoneis. Further morphological investigations performed with light and electron microscopy allowed us to describe Entomoneis annagodhei, sp. nov., with a unique set of morphological characters. Most importantly, a still undocumented character proved to be an oblique transapical fascia across the centre of the valve. Other distinctive features of this species are a pronounced raphe canal with dense raphe fibulae, very fine striation, resolvable only with electron microscopy, external lanceolate slit-like opening of the central nodule, and fine, linear to undulate external ridges running more or less parallel and adjacent to the raphe and valve margin. The morphological characters and morphometry are discussed in comparison with similar taxa. Our results contribute to the under-appreciated diversity of Entomoneis, especially inhabiting the marine plankton.