Manipulation of Whole-Lake Ecosystems and Long-Term Limnological Observations in the Brandenburg — Mecklenburg Lake District,Germany

An accompanying technical use of ecological effects from pelagic food-web interactions (biofiltration) or from sediment (nutrient remobilization) can speed up recovery of lake ecosystems and can make restoration programs more effective after external load reductions. At present the comprehensive use of multiple ecotechnological controls for water quality is limited because our knowledge of the many complex interactions, indirect effects and above all the long-term effects of such operations is insufficient. Beginning in the 1960s we started long-term limnological analyses of the trophic interactions between community structure and the flow of matter under “manipulated” conditions in whole-lake experiments at Lake Stechlin (manipulated water circulation and waste heat), Lake Haussee (biomanipulation) and Lake Fuchskuhle (lake-dividing). This paper summarises changes in abiotic and biotic structures and functions of the manipulated lake ecosystems and discusses the possibilities and limitations of “whole-lake” experiments.     

Hystrix patula与Pseudoroegneria libanotica属间杂种的细胞学研究

为研究猬草Hystrixpatula的染色体组组成,进行了H.patula与Pseudoroegnerialibanotica的人工杂交,获得杂种F1,观察了亲本和杂种F1花粉母细胞减数分裂染色体配对行为。杂种F1染色体配对较高,84%的细胞形成7个或7个以上二价体,其构型为6.08Ⅰ+7.48Ⅱ,C-值为0.69。结果表明,H.patula含有St染色体组。     

Production and cytogenetics of intergeneric hybrids between the three cultivated Brassica diploids and Orychophragmusviolaceus

It has been proposed that both complete and partial separation of the parental genomes during mitosis and meiosis occurs in the intergeneric hybrids between Orychophragmus violaceus (2n=24) and the three cultivated Brassica tetraploids (B. napus, B. carinata and B. juncea). The hypothesis has been that this and the variations in chromosome numbers of these hybrids and their progenies result from the different roles of the A, B and C genomes originating from Brassica. To test this hypothesis, we produced hybrids between O. violaceus and the cultivated Brassica diploids. The hybrids with B. oleracea (2n=18, CC) had an intermediate morphology, but their petals were purple like those of O. violaceus. They were sterile and had the expected chromosome number (2n=21) in their mitotic and meiotic cells. The hybrid with B. campestris (2n=20, AA) was morphologically intermediate, except for its partial fertility and its yellow petals, which were similar to those of B. campestris. It was mixoploid (2n=23–42), and cells with 2n=34 were most frequent. Partial separation of parental genomes during mitosis, leading to the addition of O. violaceus chromosomes to the B. campestris complement, was proposed to explain the findings in the mitotic and meiotic cells of the hybrid and its progeny. In crosses with B. nigra (2n=16, BB), the majority of the F₁ plants were of the maternal type (2n=16), a small fraction had B. nigra morphology but were mixoploids (2n=16–18), predominantly with 2n=16 cells and three plants, each with a specific morphology, were mixoploids consisting of cells with varying ranges of chromosome numbers (2n=17–26, 11–17 and 14–17). The origin of these different types of plants was inferred to be a result of the complete and partial separation of parental genomes and the loss of O. violaceus chromosomes. Our findings in the three crosses suggest that the A genome was more influential than the C genome with respect to complete genome separation during mitosis and meiosis of the hybrids with B. napus. Possible complete and partial genome separation during mitotic divisions of the hybrids with B. carinata was mainly attributed to the role of the B genome. The combined roles of the A and B genomes would thus contribute to the most variable chromosome numbers of mitotic and meiotic cells in the hybrids with B. juncea and their progenies. The possible cytological mechanisms pertaining to these hybrids and the potential of genome separation in the production of Brassica aneuploids and homozygous plants are discussed. Received: 8 February 1998 / Accepted: 12 March 1999     

Very long chain and hydroxylated fatty acids in offspring of somatic hybrids between Brassica napus and Lesquerella fendleri

 Offspring of somatic hybrids between the zero-erucic acid rapeseed cv Hanna and Lesquerella fendleri were analysed regarding their fatty acid profiles. In the first back-cross generation one plant was found that produced a seed containing up to 16.5% erucic acid and 15% eicosaenoic acid (Line 1), as well as a seed having 4.3% ricinoleic acid (Line 2). This was interpreted as due to a contribution of elongase and hydroxylase genes from the L. fendleri genome since these two fatty acids are not produced in the recipient rapeseed cultivar Hanna. Crosses between Line 1 and cv Hanna resulted in the production of seeds with 35% erucic acid (F₂). Furthermore, crosses between the F₂ plants and the rapeseed cultivar Gulle, producing 35% erucic acid in the seeds, resulted in F₃ seeds with 48% erucic acid. The highest amount of erucic acid, 61.5%, was found in the F₆ generation after crossing Line 1 with a high erucic acid rapeseed line, HEAR, followed by self-fertilisation for two generations. When performing Southern-blot analysis on the F₆ plants, seven of the nine analysed plants hybridised with the L. fendleri species-specific repetitive probe. The presence of the hydroxylase gene was also observed in the F₆ generation of Line 1 according to Southern-blot analysis. Hybridisation with a hydroxylase probe was seen although no hydroxy fatty acids could be detected in any of the F₆ plants. In parallel, Line 2 was crossed with HEAR cv Gulle and self fertilised. No hydroxy fatty acids were detected in the F₂ generation of Line 2 and no specific hybridisation patterns could be found in the Southern-blot analysis. Received: 12 December 1998 / Accepted: 4 January 1999     

Allozyme diversity in brown trout (Salmo trutta) from Central Spain: Genetic consequences of restocking

1.  The brown trout ( Salmo trutta ) represents one of the main freshwater resources in Spain, but habitat alterations and overharvesting have contributed to the decline or disappearance of numerous natural populations. In addition, reinforcement programs of wild populations based on releases of hatchery reared fish of exogenous origin compromise the conservation of remnant native trout resources.
2.  We present allozymic data from Central Spain trout populations including stocked and unstocked populations. Although the levels of genetic variation observed were low and affected by hatchery releases (p = 18.23%, Ho= 3.39%), they were within the range observed in other European areas.
3.  The effective introduction of hatchery reared fish is genetically homogenising the populations in the studied area and disturbing the ancestral pattern of genetic variation that distinguishes the Tajo and Duero basins. Within the eight natural populations analysed, seven had alleles assigned to the foreign trout. The introgression in these populations, following the LDH-5 * 90 allele frequency, ranged between 2% and 29.4%, but those values are not in concordance with the respective stocking effort undertaken in each population. Moreover, the release of hatchery-reared fish does not solve the problems related to the reduced size of wild populations and their recruitment instability.     

Microspore Culture of Hybrids Between Brassica napus and B. campestris

Embryos and regenerated plants were produced by isolated microspore culture of inter-specific hybrids between Brassica napus and B. campestris. The NLN media with different sucrose concentrations and pH values were tested and a protocol for optimal microspore culture of B. carnpestris was identified. The reciprocal hybrids between UM921 (B. campestris) and 911186 (B. napus) had significant higher embryo yield than other cultured hybrids. Obvious improvement of embryo yield and quality was achieved when hybrid plants of reciprocal UM921 × 911186 were grown under 10 ℃/5 ℃ (day/night) condition. There was significant correlation between embryo yield and seeds per pod on hybrid plants but no correlation between pollen fertility and embryo yield was detected among cultured.hybrids. The majority of microspore-derived plants from the reciprocal B. napus × B. campestris hybrids are aneuploids and 22.8% of the plants observed originated from the microspores with parent′s chromosome numbers, almost all n = 19. The factors affecting the embryogenesis in microspore culture of interspecific hybrids and the possible applications of the technique are discussed.     

洞庭湖区夏季温光条件及被迫迁移对东方田鼠繁殖的影响

在野外 ,从先年的秋初至当年春末被迫迁移前 ,东方田鼠在湖滩上能保持较高的繁殖能力 ;在夏季 ,不论栖息在农田还是岗地 ,都是东方田鼠的繁殖低谷。夏季 (6～ 8月 )在实验室自然温光条件下与人工控制较低温度条件下同时进行观察 ,结果表明 ,前种条件下东方田鼠的繁殖能力明显低于人工降低温度缩短光照条件下的繁殖力 ,此变动趋势与野外观察到的繁殖力季节动态一致 ,可以说明夏季温光条件不利于东方田鼠的繁殖。另一方面 ,东方田鼠的繁殖能力最低的 6月并非全年最热的月份 ,这是因为东方田鼠的被动迁移对体力的消耗加剧了夏季温光对繁殖的影响程度。因此 ,认为洪水引起的东方田鼠被迫迁移和夏季的温光条件共同影响了东方田鼠的繁殖。洞庭湖区东方田鼠主要在冬春季繁殖 ,而分布在高纬度地区的田鼠类动物和分布在高纬度地区的东方田鼠在夏季繁殖 ,在月份上虽不同 ,但其繁殖盛期的气温则相近 ,其实是田鼠类动物喜寒惧热特性的反映 ,乃是对当地的生态环境的适应。     

The effects of cadmium exposure on the cytology and function of primary cultures from rainbow trout

Cultured epidermal cells from explants of skin of rainbow trout were used to study the cytological and functional changes following sublethal exposure to cadmium stress. The aim was to develop diagnostic markers for ecotoxicology. Cultures were exposed to the pollutant for 48 h. Cell structural and cytological changes were established by light and electron microscopy. Metabolic alterations were detected by immunohistochemistry. The relation between the initiation of cellular alterations and cadmium concentrations was compared in cultures exposed in commercially-available serum-free and serum-containing medium. The expression of stress proteins (metallothionein and heat shock protein) was also studied. Rainbow trout epithelial cells exposed to cadmium showed typical morphological changes indicative of cell death by apoptosis. Sublethal exposure also resulted in cellular metabolic disturbances with increased deposits of glycogen. Increased melanization was also observed. These changes appeared at lower concentrations of cadmium when cells were exposed in serum-free media than in serum-containing media. Cadmium induced the expression of heat shock proteins but not of metallothioneins. The results broadly confirm in vivo findings for cadmium toxicity and suggest that this in vitro technique may have applications in aquatic toxicology. © 1998 John Wiley & Sons, Ltd.