Some new freshwater species of Paraphysomonas (Chrysophyceae)

Abstract

Examination of electron microscopical whole mounts prepared from freshly collected water samples from Danish ponds and lakes has revealed a number of hitherto undescribed Paraphysomonas species. Following the description of the new species (P. circumvallata, P. punctata, P. vacuolata, P. subrotacea, P. poteriophora, P. quad–rispina, P. coronata, P. eiffelii, P. sigillifera) the genus now contains 21 formally described species, which on account of scale morphology may be distributed within four groups. The nonperforated plate–scale (cf. P. circumvallata) , which closely resembles scales of other chrysophycean genera (e.g. Lepidochromonas, Spiniferomo–nas) , may represent a basic type of scale within the genus Paraphysomonas. Two major lines of evolution may have taken place: 1) removal of scale material through the appearance of scale apertures, and 2) an upheaval of central scale material to form a spine. Material from Greece is in some cases included, indicating at once the probable ubiquity of some of the new species. An emended description is given of P. takahashii (recently described on the basis of scale characteristics only) adding information on morphology and dimensions of whole cells. The presence of silicon in the scales has been demonstrated by X–ray analyses of two of the new species ( P. circumvallata, P. subrotacea).