Ultrastructure and taxonomy of Paraphysomonas (Chrysophyceae) and related genera 2

Abstract

This is the second of two accounts reporting on the occurrence and systematics of freshwater species of the colourless chrysophycean genus Paraphysomonas in the Cambridge area, using electron microscopy of whole mounts of both cells and scales and sections of scales. Twenty species are included here, eleven of which are new: P. cancellala, P. canistrum, P. homolepis, P. ignivoma, P. limbata, P. morchella, P. runcinifera, P. stelligera, P. stephanolepis, P. subquadrangularis and P. undulata. Five new subspecies are also established: P. circumvallata ssp. mediogranulata, P. poteriophora ssp. manubriata, P. punctata ssp. atrema, ssp. microlepis and ssp. simplicior. P. diademifera (Takahashi) comb. nov. [=Lepidochromonas diademifera (Takahashi) Kristiansen] has been included in Paraphysomonas since it has been found to be colourless and not pigmented as originally described and also to possess scales of a similar structure to those in other species of Paraphysomonas. One previously described species, P. inconspicua Takahashi, is here considered as a synonym of P. butcheri Pennick & Clarke. P. vacuolata Thomsen is removed from Paraphysomonas since it has been found to possess a chloroplast and will be included in a new genus in the third paper of this series. The 37 presently known species of Paraphysomonas have been arranged in 11 different groups according to similarities in scale structure. Consideration of the possible evolution of scale structure in Paraphysomonas and the possible interrelationships within the genus led to the conclusion that all species should be included in a single genus.