FINE STRUCTURE AND ELEMENTAL COMPOSITION OF ENVELOPES OF TWO SPECIES OF GENUS STROMBOMONAS

In the present paper,fine structures and elemental compositions of envelopes of 2 species of genus Strombomonas from natural freshwater bodies were studied.All algae were collected from different kinds of natural freshwater bodies in suburbs of Harbin city and Wuchang county and fixed with 5% formalin on the spot.In the laboratory, the specimens were separated and cleaned with redistilled water,then took pictures under light microscope (Olympus BH2).The materials for scanning electron microscopy studies were mounted onto the metal stubs with double-sided adhesive tape,dried naturally,coated with gold in an ion sputter coater,observed and took pictures under scanning electron microscope(SEM)(HITACHI S-520).After the materials were examined under SEM,they were moved to another SEM(JEDL JXA-840)to analyze their elemental compositions by energy spectrometer (OXFOD-ISIS300).The result showed:(1)Silicon(Si),aluminium(Al)and iron(Fe)were major mineralizing elements that composed of envelopes and trace magnesium (Mg),zinc(Zn)and calcium(Ca)were contained,but manganese (Mn) was not detected.Element Si was the most important among all mineralizing elements of envelopes of Strombomonas,it also appeared in envelopes of Trachelomonas generally.In order to confirm element Si existed in exogenous sands or combined onto envelopes in other ways,superficial distribution of mineralizing elements of 2 species were analyzed.The analyses showed that the distribution of element Si was relatively uniform on envelopes but was rather concentrated on particles.So the function of element Si among envelopes was complex and need further study.(2)In the studies under light microscope,granulate,tuberculate or verrucate ornamentations of envelope were used in the character description of Strombomonas usually.The surfaces of envelopes of Strombomonas were irregular and adsorbed with some particles under SEM.It was not definite to describe the envelopes of Strombomonas by those characters under light microscope and it was not definite regardornamentationas taxonomic criterion too.