Bioaccumulation of chromium and nickel in the tissues of Barbus marequensis A. Smith, 1841 from the Lower Olifants River,Mpumalanga

Bioaccumulation of chromium and nickel in selected tissues and organs of the freshwater fish Barbus marequensis was investigated. According to the monthly data, the blood accumulated the highest amount of chromium, followed by the bile and vertebrae, while the skin accumulated the lowest amount. Nickel mainly accumulated in the blood, followed by the vertebrae and gills, while the lowest nickel concentrations occurred in the fat tissue. Although significant differences (p ≤ 0,05) between localities were detected, no definite trend as to where the highest bioaccumulation had occurred could be established. The levels in the tissues and organs of B. marequensis suggested no serious chromium or nickel pollution in the study area.     

‘N vergelyking tussen agt verskillende insaaitegnieke ter verbetering van natuurlike veld

Uittreksel

‘n Statistlesbeplande veldherwinningsproef word tans in ‘n droogtebeskadigde gebied van die Soetbosveld van Transvaal uitgevoer op ontblote veld met ‘n gemiddelde reënval van 475 mm (19 duim) per jaar. Een aspek wat on‐dersoek word, is die invloed van verskillende grondbehandelings op die vestiging en produktiwiteit van ingesaaide grasse. Na afloop van die eerste groeiseisoen is 10 persent van al die behandelde bane gemonster om sowel die vestiging en hooi‐opbrengs as die plantkundige samestelling te bepaal. Die verskeie behandelings het verskillende in‐vloede op die vestiging, produktiwiteit en samestelling van die graspopulasies op die behandelde bane gehad. Behandelings wat behels het: insaai van saad, en òf losmaak van die grond òf voorsiening van ‘n bedekking van gekapte takke, het die voordeligste uitwerking gehad.     

Effect of dietary n-3 series fatty acids on sperm production in the freshwater crayfish, Astacus leptodactylus (Eschscholtz) (Astacidae)

The objective of the present work was to evaluate the effects of three different rates of long chain n-3 polyunsaturated fatty acid (LC n-3 PUFA) on the sperm number of Astacus leptodactylus. The experiment was carried out with the four following treatments: control group (not supplemented LC n-3 PUFA), D1 (1 %), D2 (2 %) and D3 (3 %). The sperm number of A. leptodactylus was counted; the reproductive system was weighted; and the macroscopical analysis of the testes and vasa deferentia (DVD) were conducted. In addition, gonado-somatic index (GI) and testes index (TI) were also calculated. The results showed that there was a significant difference between the crayfish fed LC n-3 PUFA supplemented diets (D1, D2, D3) and control in mean sperm number (P < 0.05). The highest sperm number was found for the crayfish fed D3 (6.27 ± 0.14 × 10⁸ sperm/distal vas deferens section). The results also showed that the reproductive system of the crayfish fed D3 and D2 was significantly heavier than that of the crayfish fed the control and D1 (P < 0.05). On the other hand, there was not a significant difference in the testes weight and vasa deferentia weight between the crayfish fed the control and D1, and between the crayfish fed D2 and D3 (P < 0.05). GI of the crayfish fed D3 and D2 was significantly higher than that of the crayfish fed control and D1 (P > 0.05), but there was not a significant difference in the TI of the crayfish fed control, D1, D2 and D3 (P > 0.05). In conclusion, diets containing different levels of LC n-3 PUFA significantly increase the sperm number of A. leptodactylus, and they are crucial for the production of higher number of sperm in this species.     

Proximate Chemical Composition of Whiting (Merlangius merlangus euxinus Nordmann, 1840) Roe

This research investigated the proximate chemical composition of whiting roe from October to April. The highest water content (83.99%) was found in March, while the lowest (72.40%) was found in December. The highest protein (14.54%) and lipid contents (9.71%) were found in December, while the lowest protein content (7.35%) was found in January and the lowest lipid content (0.38%) in April. Crude ash content of whiting roe changed from 0.86 to 1.49%. The highest (154 kcal/100 g) and lowest energy values (64 kcal/100 g) were determined in December and April, respectively. Whiting roe can be used as a source of valuable nutrients for human nutrition.     

ＥＭ 菌对海参养殖水体理化因子的影响

摘要：利用室内试验与池塘试验相结合的方法,研究了不同浓度的EM菌原液对海参养殖水体理化因子的影响效果。结果表明,EM菌对水体的溶解性固体（TDS）、电导率（cond）无显著影响（p>0.05）;能显著增加水体氧化还原电位（ORP）、DO、透明度（SD）（p<0.05）：其中以Ⅳ组（4*109cfu/m3）效果最好,分别平均增加3.39%（试验箱）和8.38%（试验池）、26.20%（试验箱）和18.58%（试验池）、54.69%（试验池）;pH各试验箱间缓慢下降,但差别不显著（p>0.05）,试验池比对照池平均下降3.94%,均值为7.79,仍在适宜范围内。 关键词：EM菌; 海参养殖; 水体理化因子     

天津农业高校毕业生通向农村的机制探究

天津正在社会主义新农村建设的过程中朝着沿海都市型农业的方向发展,这期间必然需要大量高等农业人才的支撑。但当前农业院校的毕业生却对农业和农村采取漠视态度。那么,如何引导天津农业高校毕业生到农村就业,成为当前亟待解决的问题。本文正是对如何引导天津农业高校毕业生通向农村就业的机制进行了探索。     

Early recognition of graft compatibility in <Emphasis Type="Italic">Uapaca kirkiana</Emphasis> Müell Arg. clones,provenances and species

Examination of callus micro-grafts in Uapaca kirkiana Müell Arg. was carried out with the objective of determining early signs of graft compatibility. Leaves from U. kirkiana, U. nitida and Jatropha curcas trees were used for callus induction. Two pieces of callus were co-cultured on Murashige and Skoog (MS) medium with different supplements. Co-cultured calli were embedded in paraffin wax and dissected. The specimens were stained in safranin and fast green before viewing under a light microscope. Results showed that MS medium with 0.1 mg l⁻¹ thidiazuron (TDZ) and 0.5 mg l⁻¹ naphthaleneacetic acid (NAA) or 1.0 mg l⁻¹ dichlorophenoxyacetic acid (2,4-D) and 0.5 mg l⁻¹ NAA was effective for callus induction. There were no necrotic layers at the unions within U. kirkiana clones and provenances, but a differential growth (irregularity) between U. kirkiana and U. nitida co-cultured calli. Phenol deposits were observed at the union interfaces of U. kirkiana combinations and were high on calli derived from mature trees. Phenol deposits were absent at the union of J. curcas heterografts. Necrotic layers developed at the unions of U. kirkiana and J. curcas micro-grafts and indicating an outright graft incompatibility. Accumulation of phenol deposits at the union interfaces inhibited graft compatibility in many U. kirkiana combinations. Callus fusion technique can be used to identify partners with an outright graft incompatibility, especially for distant related plant species.     

多杀菌素和荧光桃红B对橘小实蝇的毒力测定

为进一步筛选适合田间施用蛋白诱剂条件下的实蝇杀虫剂种类和用量,室内测定了多杀菌素和荧光桃红B分别与阮酵母水解蛋白组配后对橘小实蝇自由取食的胃毒毒性.结果表明,多杀菌素和荧光桃红B均适合与水解蛋白组配防治橘小实蝇.多杀菌素和荧光桃红B对橘小实蝇雌、雄成虫在5h内的致死中浓度分别为12.7570、13.9535和779.9378、826.6259mg/kg,16和100mg/kg多杀菌素对橘小实蝇雌、雄成虫的致死中时间分别为4.1904、4.9730h和2.4877、2.6755h,630和1000mg/kg荧光桃红B对橘小实蝇雌、雄成虫的致死中时间分别为5.3507、4.9462h和4.7650、4.5715h.     

温度和规格对波纹巴非蛤耗氧率和排氨率的影响

本研究以波纹巴非蛤为实验材料,比较了温度和规格对其耗氧率和排氨率的影响。实验温度设为15、20、25和30℃,设立了大（A）和小（B）两种规格,其壳长分别为4.35 ± 0.19 cm 和3.53 ± 0.15 cm。结果表明温度对耗氧率和排氨率存在显著影响（P < 0.05）。规格对耗氧率存在显著影响（P > 0.05）,而对排氨率影响不显著（P > 0.05）。在温度15 - 30℃之间,波纹巴非蛤的耗氧率随温度升高而增大。在15和20℃条件下,B组的耗氧率显著大于A组（P < 0.05）;在25和30℃条件下,B组的耗氧率大于A组,但差异不显著（P > 0.05）。在温度15 - 30℃之间,波纹巴非蛤的排氨率随温度升高而增大。在各温度条件下,两组排氨率没有显著差异（P > 0.05）。