4 NEW SPECIES OF PYRAMIMONAS (PRASINOPHYCEAE) FROM ARCTIC CANADA INCLUDING A LIGHT AND ELECTRON-MICROSCOPIC DESCRIPTION OF PYRAMIMONAS-QUADRIFOLIA SP-NOV

A preliminary survey of the marine nanoplankton of Northern Foxe Basin, Canada, based on observations of field material and crude cultures, has revealed nine species of Pyramimonas. Only two of these (P. nansenii and P. orientalis) have been reported previously, P. nansenii from Greenland and Denmark and P. orientalis from many parts of the world. In this paper we describe, using light and electron microscopy techniques, a species obtained in culture, Pyramimonas quadrifolia sp. nov. Pyramimonas quadrifolia is unique in scale morphology and flagellar root structure but otherwise displays characters typical of the subgenus Vestigifera. During division of the chloroplast, a structure similar to the ''plastid-dividing (PD) ring'' was observed. We also report on three new species known only from EM whole mounts of field material: Pyramimonas aurita sp. nov., Pyramimonas dichotoma sp. nov. and Pyramimonas igloolikensis sp. nov. Pyramimonas sp. is only known from its large body scales.