Improved performance of intensive semicontinuous cultures of Scenedesmus by biomass recirculation

The microscopic green alga, Scenedesmus obliquus, was used in a semicontinuous culture system for the tertiary treatment of urban wastewater, with the simultaneous production of usable biomass. Partial biomass recycling was used to increase the productivity of the system by overcoming the limits imposed by the low maximal growth rate of the alga. The biomass to be recycled was collected by simple gravity settling of the removed culture.The culture system was operated at different dilution rates and its productivity measured at each rate. An evaluation of the crude nutrient composition of the algae produced at each dilution rate was also carried out.The system was found to operate stably at dilution rates of up to 0.8 day(-1) which represents a 20% net increase over the maximum dilution rate allowed under the same conditions in a system without recirculation. The composition of the biomass produced varied little over a range of dilution rates, which may be of relevance to its projected end-use.The study indicated that such a system can exploit available light to the full and should be of particular value for the treatment of low-strength wastes such as we employed.     

New subspecies ofSparganium erectum L. from Iran

From the Caspian coastal region of Iran a new taxon,Sparganium erectum L. subsp.mazanderanicum Ponert, is described and illustrated. This new subspecies in some of its characters is near toSparganium erectum L. subsp.microcarpum (Neumann)Domin (with its east distribution trend); in other characters it is near toSparganium erectum L. subsp.neglectum (Beeby)Schinz etThell. (with ist south distribution trend). A comparative table of diacritical characters of these three subspecies is appended.     

On the validity of the genusDactylococcopsis (Cyanophyceae)

Summary The genusDactylococcopsis Hansg. 1888 (Cyanophyceae) is based on the typeD. rupestris, which was later identified as a green algae. Most of the many species described later were also placed to other groups of algae. Several authors even doubted about the existence of the genus. As, however, some species of Cyanophyceae correspond to the original generic diagnosis, the name Dactylococcopsis Hansg. ex R. et F.Chod. 1925 has been proposed as a nomen conservandum, and a new type (D. smithii R. et F.Chod.) has been defined. Further speciesD. linearis Geitl. 1935 and D.Planctonica Teil. 1942 has been unambiguously described till now.     

Chromosome counts of some Mongolian plants

The paper gives the chromosome numbers of 45 species from 72 Mongolian localities, belonging to the genera:Amygdalus, Asparagus, Astragalus, Cancrinia, Caragana, Chamaerhodos, Chelidonium, Chesneya, Dianthus, Hypecoum, Lathyrus, Lilium, Oxytropis, Papaver, Potentilla, Schizonepeta, Sibbaldia, Thermopsis, Trifolium, Trigonella, Vicia. Chromosome morphology of three species ofChamaerhodos and taxonomical remarks on some other species are added. A new combinationSibbaldia sericea (Grubov) Soják is proposed.     

Attempt at quantitative analysis of interindividual variability in stress response of leucocyte levels in mice from the viewpoint of control theory

Summary The authors studied the dependence between the ability of systems regulating the level of peripheral leucocytes to damp the fluctuations of this level, occurring under conditions of repeated stressing of the organism by non-specific stress factors (isolation, starvation, handling for blood withdrawal) and the tolerance of the organism to the action of ionizing radiation (summary exposure to X-rays leading to death at repeated irradiation). This regulatory ability was expressed with the aid of the slope (coefficientb) of regression between the leucocytary valuesx _i, fluctuating in time, and the subsequent differences _i ( _i =x _i+1–x _i ). The highest tolerance to lethal action of radiation is correlated to such a regulatory behaviour of the organism at which the time necessary for adaptation of the system is shortest. The authors point out the suitability of the employed regulatory characteristic for the quantitative study of adaptability and resistance of the organism and its relatedness to the damping ratio, used in the automatic control theory.     

Kymatocalyx Herz. in Mittelamerika

Summary A second species of the hitherto monotypic genusKymatocalyx Herz. is described and figured in detail. The new combinationKymatocalyx dominicensis (Spruce) comb. nova is proposed.     

Bemerkungen zur Variabilität vonSaxifraga marginata

Saxifraga marginata Sternb. is divided into three subspecies:S. m. subsp.marginata, S. m. subsp.bubakii (Rohlena)Chrtek etSoják,S. m. subsp.karadzicensis (Degen etKo?anin)Chrtek etSoják (environments of Skopje, Macedonia).     

Protein polymorphism inEligmodontia typus. Genetic divergence with other phyllotine cricetids

By means of gel electrophoresis of tissue extracts we have studied protein polymorphism inEligmodontia typus. The analysis was performed on specimens from five population samples collected at different sites in Patagonia (Argentina). Mean heterozygosity (\-h) and proportion of polymorphic loci (P) were determined on the basis of 19 loci. Considering all individuals as one sample, \-h gave a value of 0.16 and P was 70%. Although these values are much higher than those reported for most rodent species, they are very similar to those obtained by us for four species of the genusCalomys and forGraomys griseoflavus. There is a striking genetic identity (I_N=0.99) among populations from regions with different environmental conditions, indicating that the species possesses a common genic pool. Genetic distance with other species of the Phyllotini was estimated. D_N was lower betweenE. typus andCalomys (mean D_N=0.88) than betweenE. typus andGraomys griseoflavus (D_N=1.01). The high morphological similarity between these last two species, especially regarding those characters related to desert life adaptation, could be assigned, at least in part, to convergent evolution.