VISUALIZATION OF CRYOINJURY AND FREEZE EVENTS IN THE COENOCYTIC ALGA VAUCHERIA-SESSILIS USING CRYOMICROSCOPY

Cryomicroscopy has been used to visualise intra-and extracellular even ts during chilling and freezing the filamentous alga Vaucheria sessili s, Two cryomicroscope stages were evaluated (Planer CM3, Linkam BCS 19 6) and used to gauge the efficacy of controlled rate two-step cryopres ervation strategies on V. sessilis. Both cryostages allowed visualisat ion of dehydration, cryodehydration and deformation of the alga by ext racellular ice. Extracellular ice crushed the V. sessilis causing irre versible deformation of the cell wall with gross disruption to the int racellular architecture and rupture of the cell membrane, clearly visi ble in thawed material. The Linkam BCS 196 cryostage was operated with out ice seeding, permitted observation of supercooling events, duplica ting the conditions within a controlled rate cooler. In these investig ations intracellular-ice formation was observed, after ice nucleation of the extracellular solution, in many of the specimens examined. This paper discusses the requirement for cryomicroscope systems to simulat e the cooling regimes used in controlled-rate coolers and the use of d ifferent optical techniques in the investigation of chilling and freez ing events.