翼手目物种密度分布与环境因素的关系

本文通过划分小区和运用相关分析法,分析了翼手目|物种密度分布与主要环境因素的关系。在海拔2000米以上地区物种密度明显减少,海拔4000米以上则非常贫乏,其物种数还随纬度升高而递减。物种密度分布与年均温呈正相关关系,与相对湿度呈半对数线性关系,与日照时数呈负相关关系。但翼手目物种密度最高处并不是温湿度最高地区,而是在碳酸盐岩发达的有丰富山洞地貌的低山丘陵地区。     

ENVIRONMENTAL STRESS AND THE MAINTENANCE OF SEX IN A FRESHWATER SNAIL

Synergism among mutations can lead to an advantage to sexual reproduction, provided mutation rates are high enough (the mutational deterministic hypothesis). Here we tested the idea that competition for food can increase the advantage to sexual reproduction, perhaps by increasing the synergism among mutations in asexual individuals. We compared the survivorship of sexual and asexual snails (Potamopyrgus antipodarum) under two treatments: starved and fed. We predicted higher mortality for asexual snails when starved, but found that sexual and asexual individuals survived at the same rate, independent of treatment. These results suggest that the distribution of sex in this snail may not be explained by variation in competition among populations.     

THE DISTRIBUTION OF EDAPHIC DIATOMS ALONG ENVIRONMENTAL GRADIENTS OF A LOUISIANA SALT MARSH1

Edaphic (sediment-associated) diatoms were collected from five sites along a gradient from slightly brackish to saline marsh on 30 November 1977 and 29 April 1978. Several environmental factors change along this gradient in addition to salinity, including tidal flushing and percent organic content of the soil. A total of 112 taxa were identified, with Amphora exigua Greg., Navicula phyllepta Kütz., N. salinarum Grun., and N. tripunctata (Müll.) Bory being among the five most abundant taxa on both sampling dates. The taxonomic composition of the diatom flora was very similar to those observed for other salt marshes located along the Gulf and Atlantic coasts. Diatom taxa were generally euryhaline and distributed continuously along the gradient from brackish to saline marsh. Species diversity (H¹) and the number of taxa in a sample (S) were also similar to those reported for other North American salt marshes. The number of taxa in a sample was higher in the saline than in the brackish area on both sampling dates while species diversity was greater in the saline area only in April.     

环境因子和AM真菌分布的关系

由我国东、南沿海七省278个土样中的908个AM真菌种次分析了AM真菌属和种的分布和7种环境因子的关系。球囊霉属在各种环境下均占绝对多数,巨囊霉属＋盾巨囊霉属则为最少。球囊霉属在各pH水平土壤中分布较均匀。而其它四属主要出现在pH低于7的土壤中。摩西球囊霉C.mosseae（Nocol．＆Gerd．）Gerdemann＆Trappe在pH低于5的土壤中仍能发现。所有五属AM真菌的出现率都随土壤有机质含量增高而减少,但在有机质含量小于1．5％时出现率均稍低于1．5-3．0％;地球囊霉G．geosporum（Nicolsom＆Gerdemann）Walker的孢子数与属的规律相同,而台湾球囊霉G．formosanumWu＆Chen和弯丝硬囊霉SclerocystissinuosaGerdemann＆Bakshi则在有机质含量小于15％时数量最少。五属在不同速效磷含量土壤中的出现没有明显规律;而不同菌种对土壤含磷量有不同反应。无梗囊霉属随土壤中铁含量增加而减少其出现率;而硬囊霉属在铁含量大于15mg／kg时出现率均较多,摩西球囊霉在高于25mg／kg的土壤中明显减少而台湾球囊霉则多见于25～40mg／kg的土壤中。在15个土类中,无梗囊霉属和硬囊霉属主要分布在赤红壤和砖红壤中,前者在水稻土中也较多;台湾球囊霉主要在红壤和赤红壤中,而细四无梗囊霉A．scrobiculataTrappe则在潮土和棕壤中     

光量与球蚜发生关系的研究

在小兴安岭原始林内和采伐迹地上,发现以下几种球蚜:落叶松球蚜(Adelges laricisVall.),落叶松绿球蚜(Sacchiphanles viridis Ratz.)、落叶松红瘿球蚜(S. rosegallis Liet Tsai)、冷杉球蚜(Aphrastasia pectinatae Chol.) 以及红松球蚜(Pineus cembraepinilcoreanus Zhang et Fang),它们在林内分布和大量发生,其原因除了针叶树种类和树木     

THE PSYCHOPHYSICAL RELATIONSHIP BETWEEN COLOR AND SALT CONCENTRATIONS IN CHICKEN FLAVORED BROTHS

Taste panelists evaluated the effect of color on salt perception in chicken flavored samples using magnitude estimation. Samples were colored to simulate commercial chicken broth. Five color intensities were added to 5 NaCl concentrations ranging from 0.34 to 0.66% (w/v). Color had no influence on salt perception. Panelists were able to perceive color differences among samples (P <0.001) and these were correlated with the objective color function cot⁻¹ (a/b) calculated from the L,a,b values obtained from the Gardner XL-23. Overall flavor preference was evaluated by a taste panel using the technique of magnitude estimation. NaCl concentrations ranged from 0.52 to 0.80% (w/v). Overall flavor preference was unaffected by color. A reduction in NaCl concentration from 0.80% (w/v) to 0.52% (a 35% reduction) did not alter flavor preference. A 50 member consumer panel using a paired comparison test found no difference in flavor preference between an uncolored sample containing 0.80% (w/v) NaCl and a colored sample containing 0.72% (w/v) NaCl.     

SUBSTRATE COMPETITION BETWEEN A SALT MARSH DIATOM AND A BACTERIAL POPULATION1

Cylindrotheca closterium Ehrenberg, a benthic marine diatom, competes successfully with Aeromonas sp. a bacterium from the same environment, for low molecular weight organic substrates when they are presented at natural concentrations (1–10 μM). In short term (1 h) experiments, the uptake of mannose by C. closterium was enhanced in light. Seventy percent of the total uptake of mannose by both species was effected by C. closterium over a 1 h period in light. The diatom population was also competitive in darkness. The algal portion of glucose uptake over 1 h was 71% when both populations were given the substrate initially. Percentages of total amino acid uptake for C. closterium ranged from 33% glycine in light to 73% leucine in darkness when both species were given substrate initially. Cylindrotheca had smaller percentages of glucose and aspartic acid total uptake in competition experiments run to stationary phase (10 days).     

POPULATION ANALYSIS OF NORTHERN BOTTLENOSE WHALES IN THE GULLY, NOVA SCOTIA

Northern bottlenose whales ( Hyperoodon ampullatus ) are consistently found through the year in the Gully, a prominent submarine canyon on the edge of the Scotian Shelf. Individuals were photographically identified during field studies between 1988 and 1995. About 70% of the population is identifiable, and 29% have markings which persist reliably over periods of years. A mark-recapture analysis of photographic individual identifications collected between 1988 and 1995 indicates that the population using the Gully numbers about 230 animals (approximate 95% confidence interval 160-360). The rate of mortality plus emigration plus mark change (in animals with reliable long-term marks) is about 12% per year, although this estimate has wide and uncertain confidence limits. Members of the Gully population, which includes calves and mature males, are shorter than animals caught off Labrador. The small size of the Gully population and its persistent use of a very small, bathy-metrically unique ocean area make it vulnerable to human disturbance.     

FLUX OF INORGANIC NUTRIENTS AND PARTICULATE CARBON BETWEEN A SPARTINA MARITIMA SALT MARSH AND THE SWARTKOPS ESTUARY,EASTERN CAPE

Summary

The flux of dissolved inorganic nutrients (NH₄-N, NO₂-N, NO₃-N, SRP) and suspended particulates (particulate organic carbon POC, and particulate inorganic carbon PIC) was measured across the mouth of a small creek draining a portion of the intertidal Spartina salt marsh in the Swartkops estuary. Direct measurements of constituent concentration, the volume of water flowing into and out of the creek basin at discrete time intervals, and tidal height were made over full spring tide cycles on a two-weekly basis during a 12 month study period. Results show that the marsh acts as a sink for NH₄-N, NO₂-N, and NO₃-N on an annual basis, but exports soluble reactive phosphate to the contiguous estuarine waters. The marsh also imports nominal amounts of suspended POC and PIC (<1.5 mm in size), but apparently exports larger detrital particles (>1.5 mm) on ebb tides to the estuary. It is concluded that the marsh retains and utilizes most of its own production and functions virtually as an independent ecosystem.     

分批异养培养小球藻光密度值与干重的关系

在小球藻的分批异养培养过程中,培养液的细胞浊度（ＯＤ）与细胞干重（ＤＷ）的关系受培养条件和培养过程的影响很大,在实验中,干重与光密度值的比值在０．５３～０．２８ｇ／ＯＤ·Ｌ间变化。因此在小球藻分批异养培养过程中,培养液藻生物量检测采用单一的ＤＷ与ＯＤ换算常数用ＯＤ来推算细胞的干重则会产生较大的误差。     

THE RELATIONSHIP BETWEEN MYOFILAMENT PACKING DENSITY AND SARCOMERE LENGTH IN FROG STRIATED MUSCLE

In cross-sections of single fibers from the frog semitendinosus muscle the number of thick myofilaments per unit area (packing density) is a direct function of the sarcomere length. Our data, derived from electron microscopic studies, fit well with other data derived from in vivo, low-angle X-ray diffraction studies of whole semitendinosus muscles. The data are consistent with the assumption that the sarcomere of a fibril maintains a constant volume during changes in sarcomere length. The myofilament lattice, therefore, expands as the sarcomere shortens. Since the distance between adjacent myofilaments is an inverse square root function of sarcomere length, the interaction of the thick and the thin myofilaments during sarcomere shortening may occur over distances which increase 70 A or more. The "expanding-sarcomere, sliding-filament" model of sarcomere shortening is discussed in terms of the current concepts of muscle architecture and contraction.     

A STUDY OF THE SEED BANK OF A SALT MARSH IN NORTHERN SAN FRANCISCO BAY

Abundance, species composition, and distribution of buried seeds in a San Francisco Bay salt marsh were studied by collecting soil samples in October and February and observing seedling emergence in the greenhouse. Results were compared with existing vegetation patterns and field germination. Average numbers of buried viable seed down to a 5-cm depth were 380/ m² in October and 700/m² in February, with field germination averaging 118/m². Salicornia virginica dominated the seed bank in the greenhouse and in field germination. Most other marsh species were present in the seed bank but numbers of seeds were low. A significant correlation was found between highest species diversity and proximity to channels. The nature of this low-diversity, low-density seed bank reflects dominance of long-lived perennial species, seed dispersal patterns and selective environmental pressures.     

TILLERING AND MORTALITY OF THE SALT MARSH CORDGRASS,SPARTINA ALTERNIFLORA

Recruitment and mortality of Spartina alterniflora tillers and culms were estimated from measurements of live standing crops at Wallops Island, Virginia. Stands of tall and medium form grass produced from 452 to 1,227 tillers m⁻² yr⁻¹. Those tillered in spring lengthened into culms their first year, while those tillered in late summer and fall may have overwintered and lengthened into culms their second year. Biennial growth was most prevalent in tall form Spartina. Fifty-six to sixty-one percent of all tillers died before lengthening into culms. Of the remainder, 9 to 56% died as culms before the time of flowering. Sixty-three percent of the surviving culms of tall form Spartina flowered, compared to only 14 to 23% in medium form. Mortality of tillers and culms removed 16 to 35% of the annual production of Spartina biomass from live standing crops before the time of flowering.