水螅的培养及快速繁殖

近日发现一种喂养水螅的好饵料——水丝蚓 (鱼食 ) ,它容易获得 ,是非常好的水螅饵料。喂养的具体方法是 :将少量水丝蚓分散放入水螅培养缸中 ,因水丝蚓在水底生活 ,所以 ,在水底的水螅可直接捕捉到水丝蚓 ,在缸壁及水面上捕捉不到水丝蚓的水螅可人工喂养 ,方法是 :用吸管吸取 1条水丝蚓 ,放到水螅触手附近 ,这样水螅可直接将其缠绕捕捉 ,每天喂 1次 ,同时 ,随时清除水底异物。笔者试验用 6条水螅经 10几天的喂养后 ,发展为 2 0几条 ,而且有许多还带有 2～ 3个芽体。因食物充沛 ,水螅繁殖非常快 ,实验室中可通过食物投入的多少来控制水螅的…     

以卤虫幼体和水蚤为食物对水螅的培养比较

水蚤和卤虫幼体均是水螅培养上的常用食物,利用水蚤和卤虫幼体饲喂水螅,比较这2种食物下水螅的脱芽数和种群增长。结果表明,以卤虫幼体为食物时,水螅个体显著较大,水螅的脱芽数和种群增长明显快于以水蚤为食物时。通过卤虫卵孵化卤虫幼体喂食水螅的培养方法具有明显优势。     

以卤虫幼体和水蚤为食物对水螅的培养比较

水蚤和卤虫幼体均是水螅培养上的常用食物,利用水蚤和卤虫幼体饲喂水螅．比较这2种食物下水螅的脱芽数和种群增长。结果表明,以卤虫幼体为食物时,水螅个体显著较大,水螅的脱芽数和种群增长明显快于以水蚤为食物时。通过卤虫卵孵化卤虫幼体喂食水螅的培养方法具有明显优势。     

水螅的冬季培养

水螅生活在淡水中,在北方自然条件较差的地方不易找到,在有些条件稍好的地区可采到。为了保留这些活体,夏天可以到市场去买水蚤喂养,但了冬天,小水蚤已买不到,如何能让水螅很好地越冬,我利用水丝蚓（鱼虫）来替代水蚤喂养水螅,已获得成功,方法如下：１培养食物准...     

环境条件对水螅有性生殖的诱导

在改变水螅栖息环境条件的情况下,对水螅进行有性生殖诱导。实验结果表明,当温度在11-27℃之间进行变化,照度100lx,每天光照8h,同时食物减半的情况下对水螅进行培养实验,水螅出现了有性生殖。     

环境条件对水螅有性生殖的诱号

在改变水螅栖息环境条件的情况下,对水螅进行有性生殖诱导。实验结果表明,当温度在11-27℃之间进行变化,照度100lx,每天光照8h,同时食物减半的情况下对水螅进行培养实验,水螅出现了有性生殖。     

淡水水螅对环境因子的要求与适应

水螅是淡水生活的低等动物 ,是动物学教学和科研不可缺少的实验材料。作者通过对实验室内常年培养的4种水螅 (漠河水螅、太阳水螅、大庆水螅、哈尔滨强壮水螅 )的观察 ,浅淡水螅对生活环境的要求与适应特点。1　水质　水螅对其生活环境的水质要求比较严格 ,培养用水的清洁度对水螅的生存有直接的影响。用储放 1周以上的自来水或用充氧泵充氧 8h以上的自来水为培养用水 ( p H在 7.4～ 8.0之间 ) ,4种水螅都能正常生活。投喂食物后 ,需及时清除食物残体及排遗物 (不超过2 4 h为宜 )。清除如不及时 ,霉菌污染水质 ,造成水中乏氧 ,水螅的生存则…     

温度对水螅种群增长和个体大小的影响

应用群体累积培养法,以枝角类为食物,在10℃、20℃和30℃三种温度下,研究了温度对水螅(Hydra sp．)种群密度、种群增长率和个体大小的影响。结果表明温度对水螅种群密度和个体体积由极显著影响。在培养初期,30℃下的水螅种群密度最大;而在培养后期,20℃下的水螅种群密度则显著大于30℃下的值;10℃下的值则始终最小。在同一温度下,种群增长率均与时间呈曲线相关,10℃、20℃、30℃的回归方程分别为：Y=0．000433X^2-0．00262X 0．00332、Y=-0．003367X^2 0．068335X-0．066489、Y=-0．018469X^2 0．188952X-0．030933。在研究范围内,30℃的水螅个体最小。     

水螅的培养

水螅在教学中是腔肠动物门的代表动物 ,是良好的实验材料 ,故养好水螅对教学和科研都是重要的。1　培养用水使用储放过的自来水。即将自来水放在大玻璃缸中 ,2～ 6 d(气温高可少些 )的曝露储放 ,去除氯气 ,也称养水。如水螅放入后立即充分伸展 ,即可用来培养水螅。可用处理自来水代替养水。2　食物水螅虽可吃切碎的多种动物的肉块、水蚯蚓、孑孓、刚孵化的小鱼 ,但仍最喜食的也最方便的小甲壳动物——水蚤。3　饲养管理培养水螅的容器可根据培养数量的不同而不同。大量培养可采用大玻璃缸 ,少量培养可采用罐头瓶、大试管、小烧杯等 ,水内可…     

磁化水对水螅出芽生殖及创伤恢复后水螅出芽生殖的影响

通过经 H型磁化杯 (磁场为 4 0 m T的非均匀场 )磁化水培养正常生活的水螅和横切恢复后的水螅出芽生殖的观察 ,探索磁化水对具有两个胚层的低等水生动物细胞增殖的影响。1　材料方法1.1　材料　采用黑龙江省广泛分布的雌雄异体、实验室培养近 2年的强壮水螅 ,(H ydra robusta) ,培养液为储放两周以上的自来水 ;每天定时喂食 1次 ,食物为裸腹氵蚤 (Moina) ,摄氏 2 2～ 2 6℃条件下培养。1.2　方法1)取刚脱离亲体的水螅 2 8个 ,分成实验组 (2 1个水螅 )和对照组 (7个水螅 ) ,分别以单个水螅培养在磁化水和非磁化水培养液中。每天定时检查产…     

Food resources of shrimp-eating cichlid fishes in Lake Tanganyika

Species, size composition, and diurnal variation in abundance of shrimp (Atyidae) were examined and compared with food habits of 14 species of shrimp-eating cichlids in Lake Tanganyika. In the daytime when the cichlids foraged actively, only one species of shrimp, Limnocaridina latipes, was present on rock surfaces. Eleven of the 14 species of shrimp-eaters examined preyed mainly on L. latipes; the shrimp-eaters foraging only on rock surfaces preyed exclusively on L. latipes, whereas shrimp-eaters also taking foods from the interstices between or under stones and debris preyed on various species of shrimp. Although three kinds of shrimp-eaters, each with a unique prey catching technique and preferred shrimp size, were recognized, all shrimp-eaters preyed on shrimp of greatly overlapping sizes. This fact confirms that partitioning of food resources takes place via different capturing techniques. Moreover, the utilization of the same food resource in a different manner may promote group foraging in some shrimp-eaters, because the shrimp is a suitable animal to hunt in groups and is a quickly renewable food of potential abundance.     

Genetic analysis of developmental mechanisms in hydra. IX. Effect of food on development of a slow-budding strain (L4)

A mutant hydra strain L4 produces buds at a much lower rate than the standard wild-type strain (105) when fed with brine shrimp nauplii (T. Sugiyama and T. Fujisawa, 1979b, Dev. Growth Differ. 21, 361-375). It was found that addition of a small amount of tubifex worm tissue to the normal brine shrimp diet significantly improved the budding rate of L4 but not of 105. Detailed examination and comparison of food effect on various developmental processes in L4 and 105 have provided the following observations. (1) L4 development is strongly affected by food and has significantly lower rates than 105 in all the developmental parameters examined which involve the bud initiation process. In contrast, such effects and differences are not observed in parameters not involving bud initiation. These observations suggest that L4 has a defect(s) in its bud initiating mechanisms and that the expression of this defect is somehow strongly affected by food. (2) Epithelial cells proliferate in L4 nearly as rapidly as in 105 and without food effect. Epithelial cells produced by cell division are mostly utilized to form buds in mature 105 polyps. These cells, however, are not fully utilized for this purpose in L4 polyps which bud very slowly. Instead, they appear to be somehow lost from tissue in these animals.     

Salmonella-TEK, a rapid screening method for Salmonella species in food.

A micro-enzyme-linked immunosorbent assay (micro-ELISA) using the Salmonella-TEK screen kit was tested for the detection of Salmonella spp. in pure cultures as well as in 30 artificially contaminated food samples and in 45 naturally contaminated food samples. Different raw, fleshy foods and processed foods were used as test products. The artificially contaminated minced meat samples were preenriched in buffered peptone water, and after incubation, different selective enrichment broths were tested. The micro-ELISA optical density values after enrichment and isolation of the different broths were very analogous. The quickest method to detect Salmonella spp. in different foods is to enrich them with Salmosyst broth, which reduces the total analysis time to 31 h. The Salmonella-TEK kit for Salmonella spp. provides a promising test for the detection of Salmonella antigens in food even when they are present at a low concentration (1 to 5 CFU/25 g). The cross-reaction of the anti-Salmonella antibodies, especially to other gram-negative bacteria, is nil.     

Salmonella-TEK, a rapid screening method for Salmonella species in food

A micro-enzyme-linked immunosorbent assay (micro-ELISA) using the Salmonella-TEK screen kit was tested for the detection of Salmonella spp. in pure cultures as well as in 30 artificially contaminated food samples and in 45 naturally contaminated food samples. Different raw, fleshy foods and processed foods were used as test products. The artificially contaminated minced meat samples were preenriched in buffered peptone water, and after incubation, different selective enrichment broths were tested. The micro-ELISA optical density values after enrichment and isolation of the different broths were very analogous. The quickest method to detect Salmonella spp. in different foods is to enrich them with Salmosyst broth, which reduces the total analysis time to 31 h. The Salmonella-TEK kit for Salmonella spp. provides a promising test for the detection of Salmonella antigens in food even when they are present at a low concentration (1 to 5 CFU/25 g). The cross-reaction of the anti-Salmonella antibodies, especially to other gram-negative bacteria, is nil.     

Availability of Food Iron

Iron has been extracted from 25 common foods under conditions resembling those prevailing in the stomach under physiological conditions. In most cases less than half the iron in the foods is released into solution. The soluble iron is mainly in ionizable form, except in the case of meat products and black pudding. The amount of food iron released is influenced by cooking and the presence of iron-binding substances in some foods. The total dietary iron probably does not represent the amount available for absorption.     

The protective effect of shrimp cooked in different methods on high-cholesterol- induced fatty liver in rats

This study examined the impact of different cooking methods on fatty acid (FAs) composition of shrimp meat and the ability of these foods to protect against high cholesterol (HC) diet-induced non-alcoholic fatty liver disease (NAFLD) in rats. Shrimp were cooked for 10 min boiled, grilled, or fried in sunflower oil. Rats (n = 6/group) were fed a normal diet (ND)or high-cholesterol diet (HC) each containing boiled, grilled or fried shrimp powder (15% w/w) (NDBS, NDFS, NDGS for ND or HCBS, HCFS, HCDGS for HC diet). Frying alone significantly reduced total levels of saturated FAs (SFA) and increased total mono- and polyunsaturated FAs (MSFA, and PUFAs, respectively) in shrimp meat. It also increased levels of n-6 PUFAs and linoleic acid (LA) and decreased levels of n-3 PUFAs including eicosapentaenoic FAs (EPA) and docosahexaenoic fatty acid (DHA). When fed to HC rats, only diets containing the grilled and boiled shrimp powders significantly prevented the weight loss, lowered fasting and glucose levels, improved glucose and insulin tolerance, and prevented the increase in serum liver markers, ALT and AST. They also reduced hepatic fat accumulation, reduced serum levels and hepatic levels of cholesterol and triglycerides (TGs), reduced hepatic levels of MDA, tumor necrosis factor-alpha (TNF-α), and IL-6, and increased those of glutathione (GSH) and superoxide dismutase (SOD). No alterations in all these parameters were observed in HC-fed rats which fed fried shrimp. In conclusion, boiling and grilling but not frying are the best method to cook shrimp to preserve their fatty acid content and its nutritional value in ameliorating NAFLD.     

A numerical taxonomic study of non-motile non-fermentative Gram-negative bacteria from foods

A numerical taxonomic study using 155 unit characters was performed on 63 strains of Gram-negative non-motile non-fermentative bacteria isolated from proteinaceous foods. Similar bacteria from other sources and several Pseudomonas strains from meat were included for reference purposes. Three clusters were observed at 76% S which contained all the food strains. Cluster 1 was composed entirely of Acinetobacter strains including 17 isolated from foods that were provisionally identified with Acinetobacter johnsonii. Cluster 2 contained 22 strains identified as Psychrobacter immobilis , of which 20 were from food. Cluster 3 contained all the Pseudomonas reference strains and 26 non-motile strains isolated from meat. These were shown to be non-motile variants of Pseudomonas fragi. A simple identification scheme, based on five tests, is presented for the distinction of the three types of bacteria.     

A numerical taxonomic study of non-motile non-fermentative gram-negative bacteria from foods

A numerical taxonomic study using 155 unit characters was performed on 63 strains of Gram-negative non-motile non-fermentative bacteria isolated from proteinaceous foods. Similar bacteria from other sources and several Pseudomonas strains from meat were included for reference purposes. Three clusters were observed at 76% S which contained all the food strains. Cluster 1 was composed entirely of Acinetobacter strains including 17 isolated from foods that were provisionally identified with Acinetobacter johnsonii. Cluster 2 contained 22 strains identified as Psychrobacter immobilis, of which 20 were from food. Cluster 3 contained all the Pseudomonas reference strains and 26 non-motile strains isolated from meat. These were shown to be non-motile variants of Pseudomonas fragi. A simple identification scheme, based on five tests, is presented for the distinction of the three types of bacteria.     

Effect of Iron on Conversion of Acetic Acid to Methane During Methanogenic Fermentations

A semi-automatic method for the detection of salmonellas in food products is described. This method involves measurement of the fluorescence intensity of preparations stained with fluorescent antibody. An overall agreement of 89·6% was obtained when the method was compared with a standard cultural technique for the detection of salmonellas in foods, feeds and environmental samples, although false negatives were a problem with raw meat products. A saving in time of at least 18 h was achieved.     

Association of Empirically Derived Dietary Patterns with Cardiovascular Risk Factors: A Comparison of PCA and RRR Methods

IntroductionPrincipal component analysis is used to determine dietary behaviors of a population whereas reduced rank regression is used to construct disease-related dietary patterns. This study aimed to compare both types of DP and theirs associations with cardiovascular risk factors (CVRF).ResultsWe found that CVRF-related patterns also reflect eating behaviours of the population. Comparing concordant food groups between both dietary pattern methods, a diet high in fruits, oleaginous and dried fruits, vegetables, olive oil, fats rich in omega 6 and tea and low in fried foods, lean and fatty meat, processed meat, ready meal, soft drink and beer was associated with lower prevalence of CVRF. In the opposite, a pattern characterized by high intakes of fried foods, meat, offal, beer, wine and aperitifs and spirits, and low intakes of cereals, sugar and sweets and soft drinks was associated with higher prevalence of CVRF.ConclusionIn sum, we found that a “Prudent” and “Animal protein and alcohol” patterns were both associated with CVRF and behaviourally meaningful. Moreover, the relationships of those dietary patterns with lifestyle characteristics support the theory that food choices are part of a larger pattern of healthy lifestyle.