Flood effects on trophic linkages of selected fish species in the littoral zone of the St Lucia estuarine system,South Africa

The St Lucia Estuary, a UNESCO World Heritage Site, has experienced prolonged mouth closure since 2002. Until recently it was hypersaline, but heavy rainfall between October 2010 and January 2011 led to a large overall decrease in salinity. A stable isotope study was conducted in March 2011 on selected fish species from the nearshore environments at Charter's Creek and the estuary mouth region to determine the influence of flooding events on their diet. Oreochromis mossambicus, the dominant fish species at both sites, had a generalised diet and occupied the lowest trophic level both before and after flooding. Monodactylus argenteus, Leiognathus equula and Gerres acinaces from the mouth area displayed a largely zooplanktivorous diet and showed some changes in prey species between drought and post-flood conditions.     

The consequences of habitat occupation and habitat overlap of the introduced tilapia Oreochromis mossambicus and indigenous fish species for fishery management in a Sri Lankan reservoir

Habitat occupation and habitat overlap of the introduced tilapia Oreochromis mossambicus and co-occurring indigenous fish species were studied in a shallow lowland reservoir in Sri Lanka. Results were used to discuss the possible existence of empty habitats in reservoirs and the position of the introduced O. mossambicus in the fish community. Predictions were made of the effects of a subsidiary small-meshed gillnet fishery for indigenous minor cyprinids on the yield of tilapia. The zooplanktivorous halfbeak Hyporamphus gaimardi, an indigenous invader from brackish water estuaries and lagoons, has successfully colonized the pelagic habitat in this reservoir. The habitat of the introduced O. mossambicus overlapped significantly with those of the indigenous minor cyprinids. Only the smallest size classes of O. mossambicus (below 45 mm) arc spatially segregated from these cyprinids. Spatial distribution patterns are influenced by the rainy seasons which trigger an inshore movement of O. mossambicus and several other species around November and May. Barbus spp, (Cyprinidae) need riverine habitats for spawning, but for all other species the available habitats within the reservoir are suitable to complete their full life cycle. Exploitation of Barbus spp. with gillnets with a mesh size of 30-mm stretched mesh is predicted to have considerable detrimental effects on the existing fishery for O. mossambicus. However, a gillnet fishery with 15-mm stretched mesh to exploit Amblypharyngodon melettinus, Rasbora daniconius and H. gaimardi in the open water zone is expected to be successful without harming the existing fishery for O, mossambicus or the populations of Barbus spp.     

Comparison of the clastogenic effects of antimony trioxide on micein vivo following acute and chronic exposure

Antimony trioxide (Sb₂O₃), in aqueous suspension, was administered by gavaging to mice and monitored for chromosomal aberrations in bone marrow and sperm head abnormalities in germ cells. Acute exposur to the doses followed by observations after 6, 12, 18 and 24 h did not show any clastogenic effects. Chronic exposure daily to different doses for periods up to 21 days induced chromosornal aberrations in bone marrow. The frequencies were dose-dependent to a significant extent but no relationship could be seen with the sex of the animal. The findings indicate the harmful effects of cumulative exposure for prolonged periods to Sb₂O₃, which is being increasingly used in various industries.     

末端标记限制性片段的基因组DNA指纹法

报道了分析基因组ＤＮＡ多态性的方法：未端标记限制性片段的基因组ＤＮＡ指纹法。通过此方法对莫桑比胸非鲫核ＤＮＡ进行了初步的分析。结果表明,此方法是一种简单,灵敏,稳定,可变换带复杂程度和有着广泛应用前景的一种鉴定生物基因型的方法。     

NaCl胁迫对耐旱性不同的小麦细胞分裂效应的研究

NaCl胁迫诱导耐旱性不同的小麦(鲁麦14和晋旱47)胚根细胞有丝分裂指数下降,核畸变率和染色体畸变率与NaCl浓度和作用时间呈正相关。结果还表明:耐旱小麦晋旱47表现出较强的抗盐遗传学特性。     

NaCl胁迫对耐旱性不同的小麦细胞分裂效应的研究

NaCl胁迫诱导耐旱性不同的小麦(鲁麦14和晋旱47)胚根细胞有丝分裂指数下降,核畸变率和染色体畸变率与NaCl浓度和作用时间呈正相关。结果还表明:耐旱小麦晋旱47表现出较强的抗盐遗传学特性。     

Fine structure of chloride cells in freshwater- and seawater-adapted Oreochromis niloticus (Linnaeus) and Oreochromis mossambicus (Peters)

Ultrastructural features of branchial chloride cells in Oreochromis niloticus (Linnaeus) and O. mossambicus (Peters) adapted to both fresh water and sea water were compdred. In freshwater adapted fish of both species chloride cells showed similar morphological features. Multicellular complexes made of a mature chloride cell and one or more accessory cells sharing a single apical crypt have been observed. Whereas high percentages of 0. mossambicus survived at maximum salinity only a few individuals of 0. niloticus showed the capacity to adapt to sea water. In the seawater-adapted individuals of 0. niloficus and 0. rnossambicus the chloride cells showed a two- and three-fold increase in sizei. respectively. Most chloride cells are organized in large multi-cellular complcxcs with apical interdigitations of accessory cells and 'leaky junctions'. These results indicate that the difference in euryhalinity of the species studied is related to functional rather than structural differences.     

等离子体浸没N＋ 注入对豌豆胚芽细胞的诱变效应

报道了等离子体浸没N＋注入豌豆种子后,引起M1胚芽细胞畸变效应。初步研究结果表明：此种方法能抑制纺锤体形成,诱发胚芽细胞核畸变和染色体畸变。提出等离子体浸没离子注入可以作为一种经济、有效的诱变育种方法。Abstract: Preliminary results indicated that the pea seeds after implantation with plasma immersion ion was not only restrained spindle form but also induced plumule cell nuclear and chromosomal aberration.Being an economical and available method plasma immersion ion implantation in mutagenic breeding is proposed.     

莫桑比克非鲫卵黄形成的电镜观察

运用透射电镜观察了莫桑比克非鲫卵母细胞的生长.根据卵母细胞的大小和内部结构特征,将其分为四个时期:卵母细胞生长早期:卵黄泡形成期:卵黄积累期:卵黄积累完成期.本文着重研究了主要卵黄成分--卵黄球的形成过程.卵黄球属外源性卵黄,由卵母细胞通过微胞饮作用吸收肝脏合成的卵黄蛋白原后形成的.在卵黄大量积累前,卵母细胞内的线粒体和多泡体聚集成团,构成卵黄核,继而线粒体大量增殖,线粒体形状发生改变,形成同心多层膜结构,为大量的卵黄物质积累提供场所.最终形成的卵黄球由被膜、卵黄结晶体和两者之间的非结晶区三部分组成.     

The sulfide tolerance of milkfish and tilapia in relation to fish kills in farms and natural waters in the Philippines

Fish kills of milkfish Chanos chanos and tilapia Oreochromis spp. now occur frequently in brackish, marine, and freshwater farms (ponds, pens, and cages) in the Philippines. Aquafarms with high organic load, limited water exchange and circulation, no aeration, and high stocking and feeding rates can become oxygen-depleted and allow sulfide from the sediments to appear in the water column and poison free-swimming fish. The sulfide tolerance of 2–5 g milkfish and 5–8 g O. mossambicus was determined in 25-liter aquaria with flow-through sea water (100 ml min-1) at 26–30 °C and sulfide stock solutions pumped in at 1ml min-1. Total sulfide concentrations in the aquaria were measured by the methylene blue method and used in the regression against the probits of % survival. Four experiments showed that the two species have similar sulfide tolerance. In sea water of pH 8–8.5, about 163 ± 68 μM or 5.2 ± 2.2 mg l-1 total sulfide (mean ± 2 se) or 10 μM or 313 μg l-1 H2S was lethal to 50% of the fish in 4–8 h, and 61 ± 3 μM total sulfide or 4 μM H2S in 24–96 h (to convert all sulfide concentrations: 1 μM = 32 μg l-1). Earthen pond bottoms had 0–382 μM total dissolved sulfide (mean ± sd = 54 ± 79 μM, n = 76); a tenth of the samples had >200 μM. The water column may have such sulfide levels under hypoxic or anoxic conditions. To simulate some of the conditions during fish kills, 5–12 g milkfish were exposed to an abrupt increase in sulfide, alone or in combination with progressive respiratory hypoxia and decreasing pH. The tests were done in the same flow-through set-up but with sulfide pumped in at 25 ml min-1. The lethal concentration for 50% of the fish was 197 μM total sulfide or 12 μM H2S at 2 h, but 28–53 μM sulfide allowed fish to survive 6–10 h. Milkfish in aquaria with no aeration nor flow-through sea water died of respiratory hypoxia in 5–8 h when oxygen dropped from 6 to 1 mg l-1. Under respiratory hypoxia with 30–115 μM sulfide, the fish died in 2.5–4 h. Tests with low pH were done by pumping a weak sulfuric acid solution at 25 ml min-1 into aquaria with flow-through sea water such that the pH dropped from 8 to 4 in 5 h. Under these conditions, milkfish died in 7–9 h when the pH was 3.5. When 30–93 μM sulfide was pumped in with the acid, the fish died in 2–6 h when the pH was still 4.5–6.3. Thus, sulfide, hypoxia, and low pH are each toxic to milkfish at particular levels and aggravate each other's toxicity. Aquafarms must be well oxygenated to prevent sulfide toxicity and fish kills. This revised version was published online in July 2006 with corrections to the Cover Date.     

SO2水合物诱发蚕豆（Vicia faba）根尖细胞染色体畸变效应

以蚕豆为材料,研究SO2水合物-亚硫酸钠与亚硫酸氢钠混合液（3∶1,mmol·L^-1/mmol·L^-1）对根尖细胞的遗传毒效应。结果表明：SO2水合物处理可诱发蚕豆根尖细胞遗传不稳定,出现染色体数目和结构变异,使非整倍体和染色体结构异常明显增加。中期染色体出现了缺失、断片、环（染色体和染色单体环）、易位、双着丝粒等异常;在细胞分裂后期出现了滞后染色体、桥和断片等异常。研究结果表明,SO2是DNA分子断裂剂、非整倍体诱变剂,能够破坏生物细胞的基因组稳定性,是一种具有遗传毒性的环境诱变剂。     

Microcystin-LR equivalent concentrations in fish tissue during a postbloom Microcystis exposure in Loskop Dam,South Africa

The effects of a decomposing cyanobacteria bloom on water quality and the accumulation of microcystin-LR equivalent toxin in fish at Loskop Dam were studied in May 2012. Enzyme-linked immunosorbent assay [ELISA] was used to confirm the presence of microcystin-LR equivalent in the water and to determine the microcystin (MCYST) concentration in the liver and muscle of fish. The lowest concentration of extracellular MCYST-LR equivalent was recorded in the lacustrine zone, where no cyanobacterial cells were observed, while the highest concentration (3.25 µg l^?1), 3.25 higher than World Health Organization standard, was observed in the riverine zone. Extremely high MCYST-LR equivalent concentrations of 1.72 µg MCYST-LReq kg^?1 in the liver and 0.19 µg kg^?1 in muscles of Labeo rosae, and 2.14 µg MCYST-LReq kg^?1 in the liver and 0.17 µg kg^?1 in muscles of Oreochromis mossambicus, indicate that the consumption of sufficient fish biomass might cause severe adverse effects in humans. Microscopic analyses of the stomach content of both fish species revealed low numbers of cyanobacterial Microcystis aeruginosa cells in comparison to other phytoplankton. The extracellular MCYST-LR equivalent of the decomposing bloom may have played a major role in the high levels observed in the livers of the two fish species. These findings are important for all downstream water users.     

蛇毒心脏毒素对动物细胞的遗传损伤和生殖毒性研究

目的 应用眼镜蛇毒心脏毒素（ＣＴＸ）作用于小鼠的骨髓细胞和生殖细胞,以探讨ＣＴＸ对动物体的生殖毒性和遗传毒性。方法 对小鼠腹腔注射不同剂量ＣＴＸ,通过生殖毒性实验和致突变实验,分析孕鼠的胚胎存活率,骨髓细胞和精母细胞的染色体畸变率。结果：ＣＴＸ能影响胎鼠的生长发育,使孕鼠的增重和活胎率均明显地降低（Ｐ〈０．００１）,染色体畸变实验显示ＣＴＸ０．４ｍｇ／ｋｇ剂量上精母细胞多倍体和非整倍体细胞数目增高