VASOMOTOR RESPONSES OF ISOLATED PERIPHERAL BLOOD VESSELS FROM BOWHEAD WHALES: THERMOREGULATORY IMPLICATIONS

Temperature regulation in bowhead whales, Balaena mysticetus , is supported by the characteristic cetacean peripheral circulation, especially notable in the tail flukes. Blood vessels serving this function consist of countercurrent heat exchangers (network of veins surrounding a central artery) favoring heat conservation and an alternate routing via arteriovenous anastomoses (AVAs) providing for heat dissipation. We tested the vasomotor responses of isolated segments of countercurrent arteries and AVAs from the bowhead tail flukes to norepinephrine (NOR), the sympathetic adrenergic neurotransmitter. Isometric tension developed during exposure to a micromolar concentration of NOR was consistently higher in AVAs than in arteries. Accordingly, the AVAs are subject to sympathetic vasoconstriction, and this activation directs blood flow to countercurrent heat exchangers and results in heat conservation. In contrast, AVA relaxation by reduced sympathetic activation favors increased blood flow through AVAs and consequent peripheral heat loss.     

A Comparison of Remote Sensing and Ground-Based Methods for Monitoring Wetland Restoration Success

Abstract Efficient and accurate vegetation sampling techniques are essential for the assessment of wetland restoration success. Remotely acquired data, used extensively in many locations, have not been widely used to monitor restored wetlands. We compared three different vegetation sampling techniques to determine the accuracy associated with each method when used to determine species composition and cover in restored Pacific coast wetlands dominated by Salicornia virginica (perennial pickleweed). Two ground‐based techniques, using quadrat and line intercept sampling, and a remote sensing technique, using low altitude, high resolution, color and color infrared photographs, were applied to estimate cover in three small restoration sites. The remote technique provided an accurate and efficient means of sampling vegetation cover, but individual species could not be identified, precluding estimates of species density and distribution. Aerial photography was determined to be an effective tool for vegetation monitoring of simple (i.e., single‐species) habitat types or when species identities are not important (e.g., when vegetation is developing on a new restoration site). The efficiency associated with these vegetation sampling techniques was dependent on the scale of the assessment, with aerial photography more efficient than ground‐based sampling methods for assessing large areas. However, the inability of aerial photography to identify individual species, especially mixed‐species stands common in southern California salt marshes, limits its usefulness for monitoring restoration success. A combination of aerial photography and ground‐based methods may be the most effective means of monitoring the success of large wetland restoration projects.     

Characterization of cpsF and its product CMP-N-acetylneuraminic acid synthetase, a group B streptococcal enzyme that can function in K1 capsular polysaccharide biosynthesis in Escherichia coli

Group B Streptococcus (GBS) is the foremost cause of neonatal sepsis and meningitis in the United States. A major virulence factor for GBS is its capsular polysaccharide, a high molecular weight polymer of branched oligosaccharide subunits. N -acetylneuraminic acid (Neu5Ac or sialic acid), at the end of the polysaccharide side chains, is critical to the virulence function of the capsular polysaccharide. Neu5Ac must be activated by CMP-Neu5Ac synthetase before it is incorporated into the polymer. We showed previously that a transposon mutant of a serotype III GBS strain which had no detectable capsular Neu5Ac was deficient in CMP-Neu5Ac-synthetase activity (Wessels et al ., 1992). In this paper, we report the identification and characterization of cpsF , a gene interrupted by transposon insertion in the previously described Neu5Ac-deficient mutant. The predicted amino acid sequence of the cpsF gene product shares 57% similarity and 37% identity with CMP-Neu5Ac synthetase encoded by the Escherichia coli K1 gene, neuA . The enzymatic function of the protein encoded by cpsF was established by cloning the gene in E. coli under the control of the T7 polymerase/promoter. Lysates of E. coli in which the cpsF gene product was expressed, catalysed the condensation of CTP with Neu5Ac to form CMP-Neu5Ac. In addition, when a CMP-Neu5Ac synthetase-deficient mutant of E. coli K1 was transformed with cpsF , K1 antigen expression was restored. We conclude that cpsF encodes CMP-Neu5Ac synthetase in type III GBS, and that the GBS enzyme can function in the capsule-synthesis of a heterologous bacterial species.     

Managing the pattern of forest harvest: lessons from wildfire

Managing forests for sustainable use requires that both the biological diversity of the forests and a viable forest industry be maintained. A current approach towards maintaining biological diversity is to pattern forest management practices after those of natural disturbance events. This paradigm hypothesizes that ecological processes will be maintained best where active management approximates natural disturbance events. The forest management model now used in most sub-boreal and boreal forests calls for regularly dispersed clearcuts no greater than 60–100 ha in size. However, the spatial characteristics of the landscape produced by this model are distinctly different from the historic pattern generated by wildfire, which was heretofore the dominant stand-replacing process in these forests. Wildfire creates a more complex landscape spatial pattern with greater range in patch size and more irregular disturbance boundaries. Individual wildfires are often over 500 ha but leave patches of unburned forest within them. The combination of these attributes is not present in recent clearcuts. Allowing a proportion of larger (i.e.>500ha) harvest units may provide distinct economic advantages that could outweight the opportunity costs of leaving some patches of forest behind. For the forest type examined, further evaluation of modelling forest harvest patterns more closely after the patterns created by wildfire is required as it may achieve a good balance and strike a suitable compromise between certain ecological and economic objectives of sustainable development.     

滇金丝猴（Rhinopithecusbieti）现状及其保护对策研究

滇金丝猴（Ｒｈｉｎｏｐｉｔｈｅｃｕｓｂｉｅｔｉ）是我国特有的珍稀濒危动物,生活在海拔３８００～４３００ｍ的原始冷杉林中,但有时也会在４３００～４７００ｍ的低矮灌丛、草甸和流石滩上活动达数小时之久,甚至能跨越近千米的无林高海拔地带,因而它们是海拔分布最高的非人灵长类。松萝是它们的主要食物,取食松萝的时间占总取食时间的９１％。猴群活动范围可达近百平方公里。笔者在历时８年的野外考察中,已查明这一物种的全部现存自然种群只有１３个,分布在云南的德钦、兰坪、潍西、丽江和西藏的芒康这五县境内,其现存种群数量为１０００～１５００只;所有现存自然种群几乎均处在相互隔离的状态,群间已不可能进行基因交流,充分表明它们已到达灭绝边缘。然而其栖息地内的商业伐木规模仍在继续扩大,周围的人口压力正在不断增加,各猴群均面临不同程度的偷猎压力。这一现状委实令人担忧。如何拯救这一“国宝”应引起我国保护学家和各级政府有关职能部门的重视     

Evaluation of a remotely operated vehicle (ROV) as a tool for studying the distribution and abundance of zooplankton

Conventional methods for measuring zooplankton distributionsare too laborious and time consuming to permit sufficient temporaland spatial resolution in many instances. An ability to makemore efficient and precise measurements would be useful. Weevaluated the potential for using the video system of a commerciallyavailable remotely operated vehicle (ROV) to measure the distributionand abundance of zooplankton by calibrating ROV counts withcounts based on a conventional sampling procedure (a Schindlertrap), and by using an ROV to measure the density of zooplanktonin a small lake. As configured here, this particular ROV wassuitable for measuring the density of the cladocerans Daphniaand Holopedium. It was also suitable for assessing the distribution,but not absolute densities, of Chaoborus and Leptodora. Imagequality was inadequate for quantitative estimates of copepod(Diaptomus minutus) abundance, and prevented us from studyingbehavioral responses of copepods to the vehicle. We concludethat the ROV has at least three useful features: it can be usedto locate patches of those species that are imaged effectively;a large number of samples (videotapes) can be collected almostsynoptically with high spatial resolution; the ROV enables insitu observation of zooplankton. The ROV also has three importantlimitations: the small image volume makes it difficult to studyrare organisms; inadequate image resolution precludes studiesof relatively small organisms (e.g. the calanoid copepod D.minutus);zooplankton respond to the presence of the ROV.     

Nutrient uptake relationship to root characteristics of rice

Data on root parameters and distribution are important for an improved understanding of the factors influencing nutrient uptake by a crop. Therefore, a study was conducted on a Crowley silt loam at the Rice Research and Extension Center near Stuttgart, Arkansas to measure root growth and N, P and K uptake by three rice (Oryza sativa L.) cultivars at active tillering (36 days after emergence (DAE)), maximum tillering (41 DAE), 1.25 cm internode elongation (55 DAE), booting (77 DAE) and heading (88 DAE). Soil-root core samples were taken to a depth of 40 cm after plant samples were removed, sectioned into 5 cm intervals, roots were washed from soil and root lengths, dry weights and radii were measured. Root parameters were significantly affected by the soil depth × growth stage interaction. In addition, only root radius was affected by cultivar. At the 0- to 5-cm soil depth, root length density ranged from 38 to 93 cm cm^-3 throughout the growing season and decreased with depth to about 2 cm cm^-3 in the 35- to 40-cm depth increment. The increase in root length measured with each succeeding growth stage in each soil horizon also resulted in increased root surface area, hence providing more exposed area for nutrient uptake. About 90% of the total root length was found in the 0- to 20-cm soil depth throughout the season. Average root radius measured in the 0- to 5-cm and 35- to 40-cm depth increments ranged from 0.012 to 0.013 cm and 0.004 to 0.005 cm, respectively throughout the season. Total nutrient uptake by rice differed among cultivars only during vegetative growth. Differences in total nutrient uptake among the cultivars in the field appear to be related to absorption kinetics of the cultivars measured in a growth chamber study. Published with permission of the Arkansas Agricultural Experiment Station.     

Impact of flooding on the densities of selected aquatic insects

Data from a four-year study of five aquatic insect species,Hydropsyche betteni, H. morosa, H. bronta, Isonychia bicolor, andEphoron leucon, were utilized to evaluate the impact of a 60-year flood and a few lesser floods. The survey began in August, 1984 and was terminated in October, 1987 with the 60-year flood occurring in November, 1985. Four sampling sites were established on the South River and six quantitative samples were taken each month from each site. Gauging stations on the South River provided accurate discharge data for the sampling sites and useful historical data. Densities for the five species were utilized in the evaluation of the floods. The importance of timing is pointed out, that is, floods that occur very close together or near the end of the life cycle of an insect make it difficult to evaluate floods as disturbances. The importance of life history traits, such as behavior and egg diapause, are discussed in respect to floods. Densities were reduced to less than 50% of their average values immediately after the 60-year flood for the threeHydropsyche spp. and at three sites forI. bicolor. Ephoron leucon showed no response to the 60-year flood. Densities of the four impacted species returned to previous levels in the following generation. The 60-year flood was considered a disturbance in the near term but not for more than one generation.     

Phylogenetic relationships among transposon-like elements in human and primate DNA

A THE-1 sequence in intron 7 of the human dystrophin gene has been found to represent a new subfamily of THE-1 elements. The sequence is closely related to the MstII family of repetitive sequences and is more like single-copy sequences found in the galago genome than any other THE-1 sequence previously reported. This new THE-1 sequence has been compared with two other complete THE-1 sequences and three related long-terminal repeat elements that we have previously found in intron 7 of the dystrophin gene, and with members of the same family from elsewhere in the primate genome. Parsimony and deletion analysis show that the cluster of THE-1 sequences in intron 7 of the dystrophin gene has arisen from at least three individual insertion events, rather than from the insertion and duplication of a single progenitor sequence. Correspondence to: G.B. Petersen     

THE IMPACT OF TREE SQUIRRELS (TAMIASCIURUS) ON LIMBER PINE SEED DISPERSAL ADAPTATIONS

Tree squirrels (Tamiasciurus) are important selective agents on conifer reproductive strategies (Smith 1970, 1975). Although this is well established for wind-dispersed pines, the impact of tree squirrels on bird-dispersed pines has been largely ignored. I assessed the impact of tree squirrels on the allocation of reproductive energy in the bird-dispersed limber pine (Pinus flexilis) by comparing its cone and seed traits from three sites in the Rocky Mountains where tree squirrels (Tamiasciurus) are present to those from three mountain ranges in the Great Basin where tree squirrels are absent. As predicted, differences between the two regions in individual cone and seed traits are consistent with the hypothesis that tree squirrels are important selective agents on these traits. In the absence of tree squirrels, limber pine allocates more than twice as much energy to kernel compared with that invested in putative seed defenses (cone, resin, and seed coat) as does limber pine where tree squirrels are present. Such a large difference is particularly striking, because tree squirrels may have become extinct in the Great Basin in only the last 12,000 yr. Although many factors influence the allocation of energy to cones and seeds, no single factor other than the presence of tree squirrels is compatible with the large and consistent differences between limber pine in the Rocky Mountains and Great Basin. These results show that tree squirrels are an important constraint on the evolution of cone and seed traits that promote the dispersal of seeds by birds.