Hydroquinones from defensive secretion of a giant Pacific millipede, <Emphasis Type="Italic">Acladocricus setigerus</Emphasis> (Diplopoda: Spirobolida)

Summary. The presence of considerable quantities of hydroquinones including hydroquinone, 2-methylhydroquinone, 2,3- dimethoxyhydroquinone, 2-methoxy-3-methylhydroquinone, and 2,3-dimethoxy-5-methylhydroquinone renders the defensive secretion of Acladocricus setigerus (Silvestri, 1897) significantly different from that of other quinone-producing millipedes. In addition, two hitherto undescribed compounds, namely, 2,3-dimethoxy-5-methylhydroquinone and 2-methyl-3,4-methylenedioxyphenol, were characterized from the defensive secretion. However, it is uncertain if the latter compound is formed after the release of the secretion. The two major compounds, 2-methyl-1,4-benzoquinone and 2-methoxy-3-methyl-1,4-benzoquinone, constitute about 75% of the defensive fluid. Furthermore, hydrocarbons, which are typically present in the secretions of most other arthropods that use benzoquinones as repellents, are notably absent in the secretion of A. setigerus.     

Male capacity as related to sperm production,pregnancy initiation,and sperm competition in deer mice (Peromyscus maniculatus)

Summary Limitations on male capacity may be important to the evolution of mating strategies and behavior. Sperm counts in successive ejaculates of deer mice (Peromyscus maniculatus) decreased progressively through six ejaculations and remained depressed the following day. Males were as effective in inseminating females in cycling estrus with their second two ejaculates as with their first two and as effective in inseminating postpartum females with their fifth as with their first. In sperm competition situations males competed with rested males as effectively with their fourth, fifth, and sixth ejaculates as with their first. Thus, although sperm counts decrease in successive ejaculates, males suffer no apparent functional deficiency as long as they continue ejaculating. It is not clear whether or not deer mice are honest salesmen but they appear to be honest ejaculators and usually are honest intromitters.     

Echolocation by cave swiftlets

Summary The ability of cave dwelling swiftlets (Collocalia spodiopygius) to detect small cylindrical obstacles by echolocation was tested in a 3x9 m flight chamber. Although there was great individual variability, 6.3 mm obstacles were avoided much more often in total darkness than 1.5 wires (P<0.001). Flash photographs showed that the latter were avoided only by chance (about 50% misses). Obstacles 3.0 mm in diameter were avoided only slightly more often than 1.5 mm wires.Even in the light these swiftlets avoided the obstacles in only about 75% of the trials, probably because gentle touches with the primary feathers caused little discomfort.The 3.0 and 6.3 mm obstacles tended to be avoided more often on first encounters after they had been shifted horizontally by 10–30 cm, probably because the birds became more attentive.     

Optimum forage allocation through chance-constrained programming

Most resource allocation models developed to aid resource planning have been deterministic; that is, the ecosystem and economic variables are assumed to be known with certainty. It is these elements that present problems concerning risk and uncertainty involved in decision making. The objective of this study is to present a mathematical approach for optimizing resource allocation in management situations in which random events occur. This particular technique of decision analysis is chance-constrained programming. The model makes possible the investigation of risk and uncertainty associated with resource management decision making. Range decision-makers must often stock their range before they are sure of the available forage; thus, the amount of available forage is a random element with which managers must contend. The chance-constrained approach to decision making may be used when such random events occur and when it is not possible to plan exactly for future events. Two parameters are used to adjust the mean value of constraints; these are the standard deviation of the constraint value (S_bi) and the probability term which is specified by the manager (K_αi). The mean values are adjusted by the product K_αiS_bi. In the study reported here, a K_αi value of 0.57 gave results which appeared to have usefulness. The results indicate that the penalties a rancher must assume for over-estimating his carrying capacity are greater than the penalties for underestimating the carrying capacity. With the value of the standard deviation used in the example, numbers of livestock and the corresponding net revenues should be about 22% less than those indicated by average forage production. With greater variation in forage production, the reduction would be greater. By using these values, the chance-constrained approach can meaningfully incorporate random variables into a decision model.     

Courtship display by great frigatebirds, Fregata minor: an energetically costly handicap signal?

We used detailed time-budget observations, mark-resight data, and doubly labeled water estimates of energy expenditure to test whether energy spent on courtship display by male frigatebirds functions as a sexually selected handicap signal. During a 2-day period of time budget observations, males displayed on average 29.5% of the time (range 0–100% for 15 different males), and this value was correlated with an index of season-long display effort. Season-long display effort was strongly predictive of pairing success. Average field metabolic rate (FMR) during the 2-day time budget period was 676.5 kJ/day (range 464.8–1035.0), substantially lower than the mass-specific FMR predicted from studies of other seabirds during incubation or chick-rearing. Despite a low overall FMR, display effort could function as an energetic handicap, either if FMR correlates positively with the amount of courtship performed or if high-quality males display at a high rate because they pay a lower energy cost per unit of display than do low-quality males. We found no relationship between FMR and display rate, despite good power for doing so. We also did not find a significant difference in energy spent divided by courtship time for males that were or were not chosen by females (inferred to be high- and low-quality males, respectively), though the medians differed in the predicted direction (preferred males having lower relative costs than non-preferred males) and the confidence interval on the difference between groups was very wide. Thus, we found evidence that male courtship effort is predictive of pairing success, we rejected one mechanism by which energetic cost of display could function as a handicap, and our test of the alternate energetic handicap mechanism was equivocal.     

Study of oil-water partitioning of a chemical dispersant using an acute bioassay with marine crustaceans

The toxicity of seawater dispersions of a chemical dispersant to two marine crustaceans was investigated in the presence and absence of various quantities of a non-toxic mineral oil. From the results and a physical-chemical partitioning analysis, a limiting value of the oil-water partition coefficient of the toxic compounds is deduced suggesting that essentially all of the toxic compounds in the dispersant will partition into solution in water following dispersant application to an oil spill. This conclusion simplifies interpretation and prediction of the toxic effects of a dispersed oil spill.The combined bioassay-partitioning procedure may have applications to the study of the toxicity of other complex mixtures such as industrial effluents.     

A status report on the U.S. national dioxin study

In 1983, the US Environmental Protection Agency (EPA) embarked on an extensive investigation of the presence and extent of contamination of the national environment by CDDs/CDFs. This status report is a prelude to a final report to be delivered to the US Congress in December, 1985.     

The fate of 14C-diazinon in compost, compost-amended soil, and uptake by earthworms

A process for disposing of pesticide rinsates using sorption onto organic matter followed by composting is being evaluated. As a part of this evaluation process, we have studied the bioavailability of composted delta-2-14C-diazinon and its degradation products to earthworms (Eisenia foetida Savigny) in 30 and 60 d compost amended soil. After 60 d of composting there was considerable degradation of diazinon (95%) and a corresponding increase in the primary hydrolysis product, 2-isopropyl-4-methyl-6-hydroxypyrimidine (IMHP) as determined by high performance thin layer chromatography (HPTLC). Approximately 50% of the radioactivity became incorporated into the non-extractable fractions associated with composted organic matter with no measurable amounts of 14CO2 produced during the 60-day composting period. Following addition of the composted materials to soil, diazinon leading to 50% mortality after 14 d of exposure; continued to slowly degrade and become increasingly sorbed/entrapped within the soil-compost matrix. Soil amended with 30-d composted diazinon was toxic to earthworms whereas, no mortality was observed in those earthworms exposed to the 60-d composted diazinon. However, earthworms exposed to 30-d and 60-d composted diazinon were found to have similar levels of radioactivity in their tissues. The majority of the radioactivity in earthworms exposed 60-d composted diazinon was either unextractably bound within the earthworm tissue or was not acetone soluble. Most of the radioactivity that could be extracted with acetone was not separated by the two HPTLC methods we used. This study demonstrates that composting high concentrations of diazinon can greatly reduce toxicity and the amount of diazinon that is bioavailable to a representative soil macroinvertebrate (E. foetida).     

Modeling Flow,Nutrient, and Sediment Delivery from a Large International Watershed Using a Field‐Scale SWAT Model

A large international watershed, the St. Clair‐Detroit River System, containing both extensive urban and agricultural areas, was modeled using the Soil and Water Assessment Tool (SWAT) model. The watershed, located in southeastern Michigan, United States, and southwestern Ontario, Canada, encompasses the St. Clair, Clinton, Detroit (DT), Sydenham (SY), Upper, and Lower Thames subwatersheds. The SWAT input data and model resolution (i.e., hydrologic response units, HRUs), were established to mimic farm boundaries, the first time this has been done for a watershed of this size. The model was calibrated (2007–2015) and validated (2001–2006) with a mix of manual and automatic methods at six locations for flow and water quality at various time scales. The model was evaluated using Nash–Sutcliffe efficiency and percent bias and was used to explore major water quality issues. We showed the importance of allowing key parameters to vary among subwatersheds to improve goodness of fit, and the resulting parameters were consistent with subwatershed characteristics. Agricultural sources in the Thames and SY subwatersheds and point sources from DT subwatershed were major contributors of phosphorus. Spatial distribution of phosphorus yields at HRU and subbasin levels identified locations for potential management targeting for both point and nonpoint sources and revealed that in some subwatersheds nonpoint sources are dominated by urban sources.