Scanning electron microscopy (SEM) and light microscopy (LM) study of important characters in the identification of Sigalionidae (Annelida: Polychaeta)

Chemical variables, algae, bryophytes, and vascular plants were determined in twelve mires located in the plateau of the Sierra Segundera range. All the mires studied are minetrophic in relation to water origin, and oligotrophic poor fens in relation to water chemistry. They were classified into two types: (a) `slope mires', developed in effluent basins or depressions on slopes, usually small in size and poorly developed, and (b) `basin mires', formed in closed basins, more developed than the previous type, always including hummocks and hollows, and in some cases sedge swamps in the ponds margins.The Sierra Segundera mire system is one of the better conserved mire complexes in the Iberian Peninsula. Bryophyte and vascular plant communities were similar to those in central and northern Europe, although some Mediterranean taxa tolerating water level variation also exist. Diatomaceae were scarce whilst Cyanophyta were relatively common, which differentiate those mires from northern European ones.     

THE REQUIREMENT FOR SILICON IN SYNURA PETERSENII (CHRYSOPHYCEAE)1,2

A silicon requirement for growth is demonstrated for an alga other than a diatom. Concentrations of less than 1 μM silicate greatly decreased the growth rate of Synura petersenii Korshikov and caused morphological changes. Half of maximum growth rate (μ_max= 1.12 divisions/day) appeared at a concentration of only 0.23 μM silicate. Germanium dioxide inhibited, growth considerably; the degree of inhibition varying from none to almost 100% depending upon both Si and Ge concentrations. The amount of silicon deposited in the external scales of S. petersenii is comparable per unit area to that of diatoms. S. petersenii is able to deplete the medium of silicate to very low levels. The feasibility of batch culture techniques for this kind of work is discussed briefly.     

Records of chrysophytes with siliceous scales (Mallomonadaceae and Paraphysomonadaceae) from Finnish inland waters

Seventy-three taxa of silica-scaled chrysophytes were found with LM and TEM in 264 samples from 141 Finnish water bodies, including the genera Mallomonas (40 taxa), Synura (9), Chrysosphaerella (3), Spiniferomonas (8) and Paraphysomonas (13). More than half of the taxa are recorded for the first time from Finland and five (Mallomonas actinoloma v. actinoloma, M. favosa, M. mangofera f. gracilis, M. scrobiculata and Spiniferomonas serrata) are new to Europe. Most taxa are illustrated with TEM micrographs and the taxonomy of some interesting species is discussed in detail. The seasonal occurrence of the commonest species is described.