Licmosphenia revisited: transfer to Licmophora, redescription of L. clevei Mereschkowsky and descriptions of three new species

Abstract

Licmosphenia Mereschkowsky (Licmophorales: Licmophoraceae) is distinguished from Licmophora C. Agardh almost entirely by the presence of an apical window in the septum of the valvocopula. Recently, SEM images of three new species, all with coarse striae, showed that the valve morphology was indistinguishable from a group of Licmophora species including L. ehrenbergii, and gene sequence data showed Licmosphenia sister to the few available Licmophora spp. Two questions remain: (1) what is the structure of Licmosphenia spp. with fine striae? and (2) what would further molecular evidence contribute to understanding whether these genera are distinct or not? New LM and SEM observations on Licmosphenia species and sequence data from additional Licmophora species now answer these questions. Valve ultrastructure of a new, finely striated species with a small apical aperture, from Mallorca, Spain, is similar to finely striated Licmophora species, and the position of Licmosphenia in the phylogenetic tree is now within the Licmophora clade. The presence of apical apertures in two morphological groups of Licmophora suggests that the apical window has arisen at least twice. Licmophora is the older genus name and we therefore formally transfer all Licmosphenia species to it. In addition to Licmophora garyi from Mallorca, we describe a curved species from the Adriatic, Licmophora arcuata, similar to L. grunowii but with much coarser striae, and a species from Guam with a very large apical aperture, L. pisciformis. We also designate an epitype for Licmosphenia clevei Mereschkowsky, the type species of that genus.