Nannochloropsis limnetica (Eustigmatophyceae), a new species of picoplankton from freshwater

High densities of Nannochloropsis, reaching up to 5.7 x 10(9) cells per lit re, were observed in small inland water bodies in Germany. This is one of t he few evidences of a Nannochloropsis species in a freshwater habitat. We d escribe a new species, N. limnetica Krienitz, Hepperle, Stich ge Weller sp. nov, for which the critical taxonomic characterization is based upon 18S r RNA sequence data. The ultrastructure of this species is characterized by t he absence of a plastidial girdle lamella and pyrenoids. The plastid-boundi ng endoplasmic reticulum is continuous with the nuclear envelope, and the p rotoplasm contains numerous rodlike, doubly refringent lamellate vesicles. The pigment content of N. limnetica corresponds to that of other Nannochlor opsis, but echinone was also found. The fatty acid composition of N. limnet ica is similar to that of marine species; however, the total amount of fatt y acids (351 mu g mg(-1) C-1) is higher than in marine species.