Freshwater green algae are one of the important sources of bioenergy in the future. Spirogyra is a conjugating filamentous zygnematacean green algal genus that is widely distributed worldwide with more than 400 species. Despite its widespread occurrence throughout the world, cytological studies of the genus have been limited. We investigated karyological features and chromosome numbers for seven Korean Spirogyra species. Most of the species examined in the present study showed significant karyological features, inner organization of nucleolus, heavily stainable nucleolar substance and the diffuse-centric nature of chromosomes, typical of the Conjugales. Chromosome number ranged from n=12 in S. varians to n=38 in S. africana. Aberrant cytokinesis resulted in binucleate and tetranucleate cells, which sometimes provide cytological explanation for different morphology and ploidal changes in clonal culture of Spirogyra or even different cells within the same filament. The present chromosome data also substantiates the earlier held assumption that aneuploidy must have been the chief driving force for speciation and evolution of the genus Spirogyra.

Predation, development, and ovipostion experiments were conducted to evaluate Amblyseius swirskii (Athias-Henriot) (Acari: Phytoseiidae) as a potential biological control agent for tomato russet mite, Aculops lycopersici (Massee) (Acari: Eriophyidae) which is a periodic pest of greenhouse tomatoes. Results show that A. swirskii attacked all developmental stages of A. lycopersici, and had a type II functional response on the prey densities given. The predation rates of A. swirskii on A. lycopersici in the presense of alternative food sources such as pollen, thrips first instar, or whitefly eggs were recorded as 74%, 56%, and 76%, respectively of the predation rate on A. lycopersici alone. Amblyseius swirskii successfully completed their life-cycle on either A. lycopersici or cattail pollen. At 25oC, 70% RH, development time of female A. swirskii fed on A. lycopersici or on cattail pollen took 5.0 and 6.2 days, respectively. For the first 10 days after moulting to the adult stage, A. swirskii fed on A. lycopersici had higher daily oviposition rate (2.0 eggs per day) than on pollen (1.5 eggs per day). From this laboratory study, it can be concluded that A. swirskii has promising traits as a predator against A. lycopersici and that their populations can be stably maintained using alternative food such as cattail pollen. We suggest that the effectiveness of A. swirskii against A. lycopersici under field conditions deserves to be investigated.

Surface density distributions for globular clusters were obtained from photoelectric surface photometry (using centered aperture photometry). These surface brightness profiles were then compared with the theoretical surface density distribution of King's model. From the comparison of the theoretical and observed surface density distributions, we determine he structural parameters of the clusters (the core radius r c , the tidal cut off r t , and the concentration factor C).