桑白蚧的重要寄生蜂——桑白蚧恩蚜小蜂的鉴别与利用

桑白蚧恩蚜小蜂Encarsia(=Prospaltella)berlesel(Howard)是寄生桑白蚧Pseudaulacaspls pentagona(Targioni-Tozzctti)的重要寄生蜂,许多国家进行了引进移植,对控制桑白蚧的为害取得明显的成效．本记述了桑白蚧恩蚜小蜂形态特征的鉴别。以及各国引进利用的概况．并讨论了利用寄生蜂防治桑白蚧的重要性．     

稻螟赤眼蜂田间自然繁殖利用研究

多年调查表明,稻螟赤眼蜂是我省多择性卵寄生天敌的优势种．同时发现．稻螟蛉卵可认为是水稻上几种主要害虫天敌的天然优良寄主．由于它的被寄生率高．天敌繁殖量大．控制后继害虫的功效显,所以在水稻生产上稻螟蛉实是益大于害的．在早稻害虫防治实践中．应该减少农药使用,或避开天敌活动期和早稻前期用药．以使世代短的天敌,在近期内迅速形成庞大的种群数量。控制相继发生的二化螟、稻纵卷叶螟和稻苞虫的为害．可减少早稻用药1-2次．上述方案．无须人工生产天敌,即以田间自然繁殖保护天敌的新技术,所能达到稻田以虫治虫的功效．不亚于以往工业生产天敌的举措．实具有经济、生态和社会三方面的效益．     

Spatial and Temporal Aspects of Mixotrophy In Chesapeake Bay Dinoflagellates

ABSTRACT. Gymnodinium sanguineum, Gyrodinium uncatenum , and Ceratium furca are large phototrophic dinoflagellates that commonly form red tides in the mesohaline portion of Chesapeake Bay during the summer. Examination of protargol-stained specimens revealed that these dinoflagellates also feed heterotrophically as indicated by the presence of food vacuoles containing partially digested prey. Ingested prey were generally identified as nanociliates (≥20 μm) belonging to the oligotrich genera Strobilidium and Strombidium ; occasionally other small ciliates (e.g. Balanion sp. and Mesodinium sp.), dinoflagellates, and diatoms were observed in early stages of digestion. the percentage of these mixotrophs that had ingested prey was usually less than 20%, but approached 30% in some samples. Occurrence of food vacuoles in Gymno. sanguineum was positively correlated with ≤20 μm oligotrichous ciliate density; limited data for Gyro. uncatenum suggests a similar relationship, but C. furca feeding was not related to nanociliate densities.     

Five fundamental ways in which complex food webs may spiral out of control

Theory suggests that increasingly long, negative feedback loops of many interacting species may destabilize food webs as complexity increases. Less attention has, however, been paid to the specific ways in which these ‘delayed negative feedbacks’ may affect the response of complex ecosystems to global environmental change. Here, we describe five fundamental ways in which these feedbacks might pave the way for abrupt, large-scale transitions and species losses. By combining topological and bioenergetic models, we then proceed by showing that the likelihood of such transitions increases with the number of interacting species and/or when the combined effects of stabilizing network patterns approach the minimum required for stable coexistence. Our findings thus shift the question from the classical question of what makes complex, unaltered ecosystems stable to whether the effects of, known and unknown, stabilizing food-web patterns are sufficient to prevent abrupt, large-scale transitions under global environmental change.     

Mapping of ben genes of Pseudomonas aeruginosa

Abstract Four ben genes responsible for the conversion of benzoate to catechol in Pseudomonas aeruginosa PAO have been mapped to a 4.6 kb Kpn I fragment. ben -1 and ben -4 were known to be separate genes but now ben-1508 has been found to be different from ben-2 . The two genes were distinguished by Tn 5 mutagenesis of a cosmid clone and deletion mapping. It is likely that the four genes mapped ( ben-4, ben-2, ben-1508 and ben-1 ) correspond to the previously characterized benR (regulatory gene) and benABC (benzoate dioxygenase) respectively.     

The second life of terrestrial and plastic carbon as nutritionally valuable food for aquatic consumers

Primary production is the basis for energy and biomolecule flow in food webs. Nutritional importance of terrestrial and plastic carbon via mixotrophic algae to upper trophic level is poorly studied. We explored this question by analysing the contribution of osmo- and phagomixotrophic species in boreal lakes and used ¹³C-labelled materials and compound-specific isotopes to determine biochemical fate of carbon backbone of leaves, lignin–hemicellulose and polystyrene at four-trophic level experiment. Microbes prepared similar amounts of amino acids from leaves and lignin, but four times more membrane lipids from lignin than leaves, and much less from polystyrene. Mixotrophic algae (Cryptomonas sp.) upgraded simple fatty acids to essential omega-3 and omega-6 polyunsaturated fatty acids. Labelled amino and fatty acids became integral parts of cell membranes of zooplankton (Daphnia magna) and fish (Danio rerio). These results show that terrestrial and plastic carbon can provide backbones for essential biomolecules of mixotrophic algae and consumers at higher trophic levels.     

Winter Ciliates in a British Columbian Fjord: Six New Species and an Analysis of Ciliate Putative Prey

ABSTRACT. This work provides the first study of North Pacific planktonic ciliates by quantitative protargol staining. Triplicate water bottle samples were collected at a depth of 2 m (above the shallow pycnocline) at six stations in Indian Arm, British Columbia, on February 15, 1990, and February 26, 1991. Thirty-six ciliate species were observed. Six new species are described from protargolstained specimens: Strombidium lynni n. sp., Strombidium taylori n. sp., Strombidium basimorphum n. sp., Slrombidiurn ventropinnum n. sp., Strobilidium undinum n. sp., and Urotricha cyrtonucleata n. sp.
Ciliate abundance varied significantly (ANOVA, α= 0.05) between sampling sites, ranging from 550 to 6,800 cells/liter in 1990 and from 1,800 to 7,900 cells/liter in 1991. Biomass also varied significantly (ANOVA, α= 0.05) ranging from 3.7 × 10⁵ to 3.3 × 10⁶ pg carbon/liter in 1990 and 3.04 × 10⁶− 6.97 × 10⁶ pg carbon/liter in 1991. Putative prey were enumerated in three size fractions (1.5–5 μm, 5–10 μm and 10–25 μm). The source of variation in ciliate abundance and biomass was not identified. Parameters of salinity, temperature, putative prey, chlorophyll a and pycnocline depth did not significantly correlate with ciliate biomass or abundance (α= 0.05).     

Food intake and mass gain of hand-reared brown bear cubs

Five orphaned European brown bear cubs (Ursus arctos) from 3 litters were hand-reared from the ages of 1–4 months. Body mass initially ranged from 1.7 to 2.8 kg. Growth rates were monitored with reference to diet. Over a period of 3 years, 6 different feed formulas were used. The first 4 formulas were given with bottles until an average age of 133 days. Conversion to mass in the first 10 months ranged from 3.5 to 32.0 g of food per gram of body mass (or 38.1–192.6 kJ of gross energy/gram body mass), and was affected by type of diet. High fat content increased, whereas high carbohydrate content decreased the conversion rates. Formula 3, with 12.0% protein, 23.9% fat, and only 0.2% carbohydrates, simulated values found in bears' milk and produced the best growth rates. Formula 6 (bread, fruits, and meat) was used from ages 7 to 35 months, and over this period, the efficiency of gross energy conversion decreased gradually, by an eventual factor of 3.8. Hand-reared cubs ranged from 1.3 to 2.7 times heavier than 17 wild cubs measured at matching ages. Wild mass is probably limited by maternal hibernation, and by the largely herbivorous nature of the diet. © 1993 Wiley-Liss, Inc.     

Temporal pattern of resource use and variation in diets of individual grasshoppers (Orthoptera: Acrididae)

Patterns of resource fidelity, switching, and variation in individual diet were examined in the polyphagous grasshopper Taeniopoda equesforaging in experimental cages over an 11-day period. Ten novel dicots were provided in the cages, but grasshoppers fed primarily on kale (Brassica oleraceavar. acephala),lobelia (Lobelia erinus),pansy (Viola x wittrockiana),and dry bermuda grass (Cynodon dactylon).Grasshoppers showed significant fidelity to a single plant within a meal but tended to eat less of the same plant in the next meal and, in the case of pansy, on the next day. Grasshoppers switched nonrandomly, suggesting that compensatory feeding on complementary resources may have occurred. There was no evidence that behavioral interactions among individuals increased switching rate or lowered fidelity. Overall patterns of resource use varied significantly among grasshoppers during the study, despite frequent switching among resources and a significant tendency to aggregate while feeding. All individuals were polyphagous but differed in relative consumption of available plants. The results suggest that individual grasshoppers express different feeding patterns that are consistent over time and that variation in diet among individual observed in the field may be more than simple sampling error.