Hearing Range of White-Tailed Deer as Determined by Auditory Brainstem Response

Abstract: Basic knowledge of white-tailed deer (Odocoileus virginianus) hearing can improve understanding of deer behavior and may assist in the development of effective deterrent strategies. Using auditory brainstem response testing, we determined that white-tailed deer hear within the range of frequencies we tested, between 0.25–30 kilohertz (kHz), with best sensitivity between 4–8 kHz. The upper limit of human hearing lies at about 20 kHz, whereas we demonstrated that white-tailed deer detected frequencies to at least 30 kHz. This difference suggests that research on the use of ultrasonic (frequencies >20 kHz) auditory deterrents is justified as a possible means of reducing deer—human conflicts.     

Impact of density of Aphis craccivora (Aphididae) on growth and yield of susceptible and resistant cowpea cultivars

Impact of initial density of cowpea aphid Aphis craccivora Koch (Aphididae) at infestation on the growth and yield of aphid-susceptible cowpea cultivar ICV-1 and aphid-resistant cultivar ICV-12, was investigated. Plants at the seedling, flowering and podding stages of development were infested with five aphid densities consisting of 0, 2, 5, 10 and. 20 aphids per plant and maintained for 22 days. Extended leaf heights of plants and aphid counts were recorded at 7, 12, 17 and 22 days after infestation. Two crop growth parameters (biomass duration and leaf area duration), and two plant yield parameters (number of pods per plant and number of seeds per pod) were recorded. Due to the occurrence of parthenogenesis and changes in population dynamics during infestations, aphid densities were converted into cumulative cowpea aphid-days, to facilitate data analyses and interpretation. ANOVA indicated that there was significant (P=s 0.05) difference in aphid-day accumulations between the two cultivars when infested at the seedling stage. Accumulations on cv. ICV-1 were greater than on cv. ICV-12. However, no such differences between the cultivars were detected when plants were infested at flowering and podding stages. Therefore, the seedling stage was used for comparisons of the impact of cowpea aphid-days on the growth and yield parameters of the two cultivars. At the 95% confidence intervals, ICV-12 plants were consistently taller than ICV-1 plants. Infested ICV-1 seedlings showed stunting and other growth deformities which were not observed on ICV-12 plants. Regression analyses revealed substantial reductions in the growth and yield parameters of ICV-1 relative to ICV-12. Overall, cowpea aphid-days provided a convenient and reliable method for studying the aphid population dynamics and the subsequent impact on plant growth and yield performance.     

A comparison of canopy evapotranspiration for maize and two perennial grasses identified as potential bioenergy crops

In the Midwestern US, perennial rhizomatous grasses (PRGs) are considered one of the most promising vegetation types to be used as a cellulosic feedstock for renewable energy production. The potential widespread use of biomass crops for renewable energy production has sparked numerous environmental concerns, including the impacts of land‐use change on the hydrologic cycle. We predicted that total seasonal evapotranspiration (ET) would be higher for PRGs relative to maize resulting from higher leaf area and a prolonged growing season. We further predicted that, compared with maize, higher aboveground biomass associated with PRGs would offset the higher ET and increase water‐use efficiency (WUE) in the context of biomass harvests for liquid biofuel production. To test these predictions, ET was estimated during the 2007 growing season for replicated plots of Miscanthus×giganteus (miscanthus), Panicum virgatum (switchgrass), and Zea mays (maize) using a residual energy balance approach. The combination of a 25% higher mean latent heat flux (λET) and a longer growing season resulted in miscanthus having ca. 55% higher cumulative ET over the growing season compared with maize. Cumulative ET for switchgrass was also higher than maize despite similar seasonal‐mean λET. Based on total harvested aboveground biomass, WUE was ca. 50% higher for maize relative to miscanthus; however, when WUE calculated from only maize grain biomass was compared with WUE calculated from miscanthus harvested aboveground biomass, this difference disappeared. Although WUE between maize and miscanthus differed postsenescence, there were no differences in incremental WUE throughout the growing season. Despite initial predictions, aboveground biomass for switchgrass was less than maize; thus WUE was substantially lower for switchgrass than for either maize scenario. These results indicate that changes in ET due to large‐scale implementation of PRGs in the Midwestern US would likely influence local and regional hydrologic cycles differently than traditional row crops.     

Testing the Adaptive Significance of Acclimation: A Strong Inference Approach

Acclimation is a common phenotypic response to environmentalchange. Acclimation is often thought to enhance performanceand thus to be adaptive. This view has recently been formalizedas the "Beneficial Acclimation Hypothesis" and predicts thatindividuals acclimated to one environment perform better inthat environment than do individuals acclimated to a differentenvironment. Although Beneficial Acclimation is appealing andwidely supported, recent studies with E. coli and Drosophilahave challenged its general validity. Although these challengescould be dismissed as mere exceptions, they encourage a re-evaluationof the adaptive significance of acclimation. Our philosophicalapproach differs from that of most previous studies of acclimation,in which the prediction derived from a Beneficial Acclimationperspective (e.g., heat tolerance is positively correlated withacclimation temperature) is tested against the null hypothesis("single hypothesis approach"). Instead, we follow Huey andBerrigan (1996) in advocating a strong inference approach (sensuPlatt, 1964), which recognizes that Beneficial Acclimation isactually one of a set of competing hypotheses that make differentpredictions as to how developmental temperature influences thethermal sensitivity of adults ("developmental acclimation").Using this perspective, Huey and Berrigan proposed a factorialexperimental design (3 developmental by 3 adult temperatures)designed to discriminate among all competing hypotheses. Wenow derive a formal statistical model (ANOVA with orthogonalpolynomial contrasts) for this experimental design and use itto evaluate simultaneously the relative impact of each competinghypothesis. We then apply this model to several case studies(Drosophila, Volvox, Trichogramma), and we review also a recentstudy with E. coli. The influence of Beneficial Acclimationis supported (albeit often weakly) in most cases. Nevertheless,other hypotheses (especially the Optimal Developmental TemperatureHypothesis) often have a greater impact. Even so, however, BeneficialAcclimation usually predicts relative performance at extremetest temperatures. We conclude that, although rumors of itsdeath are premature, Beneficial Acclimation cannot be viewedas the dominant expectation, at least with regard to developmentaltemperature acclimation. Moreover, our findings reinforce theview that a strong inference approach provides a more comprehensiveportrait of complex biological responses than do single-hypothesisapproaches.     

N<Superscript>6</Superscript>,O<Superscript>2</Superscript>′-Dibutyryl Adenosine 3′,5′-Monophosphate induces Pigment Production in Melanoma Cells

IN VITRO studies have suggested that adenosine 3′,′-monophosphate (cyclic AMP) regulates cell morphology. During treatment with the dibutyryl analogue of cyclic AMP, N⁶,O²′-dibutyryl cyclic AMP, transformed fibroblasts acquire several morphological characteristics of untransformed fibroblasts^1,3. Cell processes are extended, the cells occupy a greater surface area and in some cases there is a parallel alignment of cells. Chinese hamster ovary cells are affected in the same way. In neuroblastoma cells⁵, dibutyryl cyclic AMP induces neurite extension and increases the activity of acetylcholinesterase, an indicator of biochemical differentiation⁶. Cyclic AMP is known to control the dispersion of melanin^7,8 and the differentiation of melanoblasts into melanocytes. We have now found that during treatment with dibutyryl cyclic AMP, melanoma cells spread out, appear larger and produce considerably more pigment than untreated cells.     

The Effects of Salinity upon Galactosyl-Glycerol Content and Concentration of the Marine Red Alga Porphyra purpurea (Roth) C.Ag.

Changes in the major alcohol-soluble, low molecular weight carbohydratesof P. purpurea, O--D-galactopyranosyl-(1-2)-glycerol (‘floridoside’)and O--D-galactopyranosyl-(1-1)-glycerol (‘isofloridoside’),have been examined in response to salinity variation. ‘Floridoside’is shown to vary in absolute amount, increasing in hypersalineand decreasing in hyposaline media. ‘Isofloridoside’content per cell does not change in a similar manner. Responsesare almost identical under light or dark conditions, ‘floridoside’changes being complete within 24 h. Decreasing the externalwater potential using ionic and non-ionic solutes has the sameeffect upon galactosyl-glycerol content. The amount of ‘floridoside’synthesized, and degraded under hypersaline and hyposaline conditionsrespectively is shown to be insufficient to restore cell volumeto its original value. It is therefore suggested that the primaryfunction of ‘floridoside’ increases in concentratedsea-waters is that of a compatible solute, serving to protectthe cell during periods when the external salt content is increaseddramatically.