|
Further progress in plankton ecology is connected with the development of methods for organism observation in their natural habitats. Investigation of processes and phenomena taking place in microvolumes of the water environment is becoming more and more topical. Possibilities, advantages and limitations of holography applied to zooplanktonic studies in Lake Baikal are estimated in the paper. Peculiarities of the Lake Baikal zooplankter holographing are studied in laboratory experiments. The endemic pelagic crustacean Macrohectopus branickii (Amphipoda) was one of the objects studied. Images of the crustacean body fragments (5 - 40 micrometers and more) allowed us to estimate the resolution of holographic methods for different distances from the hologram plane. The resulting holograms reveal the interior of hard chitin structures (spines and other body parts). It is possible to count and to size the less hard structures (e.g., setae). A lot of biological particles are transparent or semitransparent and holographic image of such particle differs from the opaque particle image. Peculiarities of holographic images of these particles are discussed in the paper. As a result, we proposed method for evaluation of the particle optical features (refractive index and absorption factor), in addition to its geometrical parameters. The additional information can provide more precise identification of particle type. Method is based on analysis of intensity distributions in various cross- sections of holographic image. The above technique has been applied to experimental measurements of the refractive index of water drops in the air, latex spheres in various liquids, air bubbles in water. The accuracy of measurements was about 10% for the particles of 100 micrometers in diameter. Results of holographing of biological microparticles are presented as well.
|
