MINERALOGY AND RADIOISOTOPE RETENTION PROPERTIES OF A CHRONOSEQUENCE OF SOILS DEVELOPED IN BASALTS OF VICTORIA, AUSTRALIA

The mineralogical composition and retention properties for radioisotopes (²⁰Sr and ¹³⁷Cs) of soils developed in five basalt flows of age varying from 6000 years to about four million years occurring in western Victoria were investigated. The trend of mineral weathering has been almost exclusively to amorphous material, kaolinite-plus-halloysite, and chlorite, the more soluble products of weathering having been removed. The most significant changes in clay mineralogical composition with time are the progressive decrease in the Si0₂/Al₂O₃ molar ratio of the amorphous material in the clay fraction of the surface horizons, from an initial value of approximately 4 to values of approximately 2, and the progressive increase in the amount of kaolinite-plus-halloysite, both in the topsoil and at depth, with age of the basalt flow. The amount of kaolinite plus halloysite increases from approximately 20 per cent of the clay of soil developed in the basalt flow 6000 years old to approximately 50 per cent of that of soil in basalt about four million years old. Evidence for the presence of halloysite was obtained by electron microscopy studies. The amorphous material and chlorite contents, each of which constitutes between 20 and 50 per cent of the clay fractions, decrease concurrently with the increase in kaolinite-plushalloysite content. Fixation of Sr by whole soil samples was controlled by the organic matter and free iron oxide contents rather than by the mineralogy of the samples. A high proportion of the added Cs was sorbed by whole soil samples. Much of the sorbed Cs was not readily replaced by CaCl, washings but was replaced in part by subsequent washing with NaCl of pH 5.3 and almost entirely by subsequent NH₄Cl washings. Much of the Sr and Cs deposited on these soils by rainfall and dry fall-out would be sorbed; the ease of replacement suggests that these elements would be available for further movement through the food chain.     

Effects of Hormonal Supplementation on Nuclear Maturation and Cortical Granules Distribution of Canine Oocytes During Various Reproductive Stages

The aim of this study was to evaluate the effects of hCG, progesterone and oestradiol supplementation on nuclear and cytoplasmic maturation of canine oocytes cultured for 24, 48, 72 and 96 h. Oocytes obtained from 18 healthy bitches were divided into three groups according to their reproductive status (follicular, luteal and anoestrus stages) and cultured in TCM 199 + 25 UI/ml of hCG + 1 μg/ml of progesterone + 1 μg/ml of 17‐β oestradiol or without hormonal supplementation (control) for different periods. Then, they were stained with FITC‐LCA‐Hoescht for chromatin configuration and cortical granules distribution and evaluated under an epifluorescence microscope. Culture time and the influence of different stages of the oestrous cycle were also evaluated. The present study demonstrated that there was no significant difference among the reproductive stages. With regards to culture medium, only oocytes from the supplemented medium were able to complete meiosis; however, significant difference was only noticed in the percentage of MI stage oocytes (p < 0.05) in the follicular and luteal group at 72 h of culture. Most oocytes in germinal vesicle, germinal vesicle breakdown and metaphase I stage had cortical granules distributed throughout the cytoplasm (immature pattern), irrespective of the culture period (p < 0.05). Cortical granules distributed immediately beneath the plasma membrane (mature) was only observed in metaphase II stage oocytes, but not all of them presented matured cytoplasm. Our results reveal that cortical granules distribution in canine oocytes matured in vitro did not progressed in correspondence with nuclear stage changes and are in accordance with those from other species.     

Weight and measurement data on tortoises (Testudo graeca and Testudo hermanni) and their relationship to health

Normal bodyweight and carapace lengths for two species of tortoise are presented and a comparison made with changes in bodyweight in sick tortoises. Using these parameters veterinary surgeons will have guidelines for assessing the degree of debility in a tortoise of any age or size. A number of examples are given.     

Effects of supernumerary chromosomes on production of pigment in Haplopappus gracilis

One of the two types of supernumerary chromosomes found in Haplopappus gracilis effects pigment production in the achene walls. When one, two, and four supernumerary chromosomes were added to the basic complement, a corresponding increase in the amount of one type of pigment was found to occur. No overlapping of the effects on pigment production was observed among different numbers of supernumeraries or between the supernumeraries and normal chromosome complement.