Ornamentation of thecal plates in Protoperidinium (Dinophyceae) as seen by scanning electron microscopy

Abstract

The thecae of over thirty species of Protoperidinium from around the British Isles have been examined by SEM and the various types of ornamentation described. The simplest type consists of smooth plates in which the trichocyst pores have an even or irregularly thickened rim. In one species the pores are situated on mounds. In another variation the plates are covered with minute pimples. Many species have plates which are thickened by a surface reticulum and this may be made up of lines of pimples, of irregularly arranged ridges or bars which protrude to form small spines. In one species the ridges always surround trichocyst pores and in another there are prominent spines which bear no obvious relationship with the pores. It is concluded that thecal ornamentation can provide useful taxonomic characters within this genus.