Taxonomy,morphology and ecology of some widespread representatives of the diatom genus Opephora

Opephora parva, O. pacifica and O. perminuta are commonly reported from brackish and marine sediments worldwide, but their true identity is unclear. Therefore, isotype material of these three taxa was examined using light microscopy. In addition, several populations from different localities in Europe, Africa, South America and Australasia were investigated with light and scanning electron microscopy. In the isotype slide of O. parva and O. perminuta, four different opephoroid taxa could be distinguished; three new combinations are proposed. The correct name of O. parva is O. mutabilis (Grunow) comb. nov.; this is a distinct, valid species, and is usually reported under the later synonym O. olsenii. O. perminuta is transferred to the genus Pseudostaurosira; P. perminuta (Grunow) comb. nov. The two other taxa were identified as O. naveana Le Cohu and O. guenter-grassii (Witkowski & Lange-Bertalot) comb. nov., which is transferred from the genus Fragilaria. These four taxa were then compared with isotype material of O. pacifica (Grunow) Petit. A detailed description of their taxonomy, morphology and ecology is given. Although Opephora mutabilis, O. naveana and O. guenter-grassii differ in some respects from O. pacifica, the type of the genus, their maintenance in this genus is recommended subject to further research.