Allocation of reproductive effort in Mus domesticus: responses of offspring sex ratio and quality to social density and food availability

Summary Female mammals in good condition can maximize their inclusive fitness by investing more in male offspring than in female offspring during periods of poor environmental quality. To test this hypothesis, we measured the effects of undernutrition and crowding before and during gestation on the sex ratio and weight of offspring at parturition and at weaning in Mus domesticus. Sex ratio was not significantly affected by density. Dams altered the sex ratio of their offspring in response to food availability, but only if variance in competitive success within the experimental subpopulation was evident. Thus ad lib fed females produced litters with an unbiased sex ratio, competitively successful females under moderate food availability produced a male-biased sex ratio, and severely food deprived females produced litters with a female-biased sex ratio. In groups that experienced competition for food, successful dams favoured male offspring during lactation. These results are consistent with the predictions of Trivers and Willard (1973). Analysis of within-cell variance and covariance suggests that the interaction of social structure and food availability provides specific cues for the dams' tactical reproductive choices.     

Total body zinc concentration and allometric growth ratios in Mytilus edulis collected from different shore levels

Body zinc concentrations (on a soft parts dry weight basis) in 18 composite collections of mussels (Mytilus edulis) taken from different shore levels within a single mussel bed on the north shore of the Tyne estuary at Tynemouth, on 25 October, 1980, showed highly significant correlations with 4 allometric, size-related factors. A negative correlation was found between body zinc concentration and a flesh condition (FC) index defined as mg dry flesh wt per g dry shell wt. Positive correlations were found between body zinc concentration and width: height ratio, width: length ratio and shell valve inequality index (SVI) defined as the weight of heavier shell valve/weight of lighter shell valve. Unlike earlier observations on a single population taken from a single habitat, this heterogeneous collection showed no significant relationship between body zinc concentration and body size as determined by soft-parts dry weight. Body zinc concentration and allometric ratios were, however, related to position on the shoreline. It is suggested that, where mussels are collected from different habitats, environmental factors probably have a greater influence on body size than age. Therefore, normalization of trace metal concentrations to a standard body weight may not be appropriate where specimens are collected from a variety of habitats. Allometric ratios are related to age, but are independent of absolute size, and may therefore provide a more suitable basis for normalization of trace metal concentration within a monitoring programme.Contribution No. 1222 of the Center for Estuarine and Environmental Studies of the University of Maryland     

No evidence for acoustic mate-guarding in duetting buff-breasted wrens (Thryothorus leucotis)

There are few empirical tests of the acoustic mate-guarding hypothesis for the function of duetting in birds. This hypothesis states that when females are fertile, males initiate many songs or answer most of their mates solo songs to form duets and repel rival males seeking extra-pair copulations. We tested the hypothesis by comparing song initiation and answer rates of males and females in socially monogamous buff-breasted wrens (Throthorus leucotis) during pre-fertile and fertile periods. During pre-fertile periods, males often sang for short periods before being answered by their mates, yet first duets were formed earlier relative to dawn and more duets were given during the dawn chorus on pre-fertile than fertile mornings. Males initiated more songs during pre-fertile than fertile periods, whereas there was no difference between stages in female song initiation rates. The proportion of songs answered by individuals of both sexes did not differ between breeding stages. Other mate-guarding behaviours, such as frequent copulation and maintaining close proximity to mates when fertile, did not appear to be important in this species, as no copulations were observed and there was no difference in the time pairs spent in close proximity when females were fertile or not. Parentage analysis revealed that only 3% of 31 broods had young that were likely the result of extra-pair paternity. These findings do not support the acoustic mate-guarding hypothesis, and suggest that the low rate of extra-pair paternity in buff-breasted wrens was maintained without the use of acoustic or traditional paternity guards.Communicated by R. Gibson     

Condition-dependent control of paternity by female purple martins: implications for coloniality

Proposed causal links between extra-pair copulation (EPC) and colony formation in socially monogamous birds hinge on the question of which sex controls fertilizations. We examined in colonial purple martins Progne subis (1) whether EPCs were forced or accepted by females, and (2) the degree to which apparently receptive females were able to obtain EPCs against their mates’ paternity defenses. Paternity analyses of multilocus DNA fingerprinting confirmed previous findings of a marked relationship between age class and extra-pair fertilizations (EPFs), with young males losing paternity of 43% (n = 53) of their putative offspring compared to 4% (n = 85) by old males. All assignable extra-pair offspring were sired by old males, with one male obtaining most EPFs each year. Contrary to the hypothesis that EPCs are forced, EPF frequency within age class did not increase with seasonal increases in the number of males per fertile female. Whereas the male control hypothesis predicted that the male age class that mate-guarded more would be cuckolded less, the reverse was true: young males guarded significantly more intensely. The male age class difference in cuckoldry could not be explained by the possibility that young and inexperienced females (which are usually paired to young males) were more vulnerable to forced copulation because EPFs were unrelated to female age. These findings suggest that females (1) pair with old males and avoid EPCs, or (2) pursue a mixed mating strategy of pairing with young males and accepting EPCs from old males. The receptivity to EPCs by females paired to young males put them in conflict with their mates. Two factors determined the paternity achieved by young males: (1) the relative size of the male to the female, with young males achieving much higher paternity when they were larger than their mates, and (2) the intensity of mate-guarding. Both variables together explained 77% of the variance in paternity and are each aspects of male-female conflict. Given female receptivity to EPCs, mate-guarding can be viewed as male interference with female mating strategies. We conclude that EPCs are rarely or never forced, but the opportunity for females paired to young males to obtain EPCs is relative to the ability of their mates to prevent them from encountering other males. Evidence of mixed mating strategies by females, combined with other features of the martin mating system, is consistent with the female-driven “hidden lek hypothesis” of colony formation which predicts that males are drawn to colonies when females seek extra-pair copulations. Received: 23 March 1995/Accepted after revision: 14 January 1996     

Begging signals more than just short-term need: cryptic effects of brood size in the pied flycatcher (Ficedula hypoleuca)

The begging of nestling birds is known to reliably signal short-term nutritional need, which is used by parents to adjust rates of food delivery and patterns of food distribution within broods. To test whether begging signals reflect more than just short-term feeding history, we experimentally created 18 "small" (4-nestling) and 18 "large" (8-nestling) broods in the pied flycatcher (Ficedula hypoleuca). Compared to small broods, large broods were provisioned by parents at a greater rate, but at a lower visit rate per nestling and with no obvious differences in load mass per visit. However, lower rates of food mass delivery per nestling in large broods did not result in any measurable reduction in nestling growth (i.e. "long-term need") or in any increase in the begging effort per individual nestling whilst in the nest. Mid-way through the nestling period we also used hand-feeding laboratory trials to assess in more detail individual begging behaviour and digestive performance of the three mid-ranking nestlings from each brood. More food items were required at the start of each trial to satiate nestlings from large broods, but despite this initial control for "short-term need", nestlings from large broods went on to beg at consistently higher rates and at different acoustic frequencies. Large brood nestlings also produced smaller faecal sacs, which were quantitatively different in content but did not differ in frequency. We suggest that different nutritional histories can produce cryptic changes in nestling digestive function, and that these can lead to important differences in begging signals despite controlling for short term need.     

The occurrence of glycolic acid in coastal sea water

A reasonably fast and reliable chemical method for the determination of glycolic acid in sea water is described in detail. It consists of adsorption of glycolic acid by alumina, followed by extraction with sulphuric acid and then colorimetry. The overall efficiency of recovery of this method, which is standardized internally, is approximately 67%, and about 20-fold concentration of glycolic acid is achieved. Using this method, the occurrence of glycolic acid in Ipswich Bay (Gulf of Maine, USA) was studied over a period of 6 months and was found to fluctuate between 0 and 80 g/l. The zero values occurred in January, when the phytoplankton chlorophyll values were also at their winter minimum.     

Temperature tolerance of embryos and larvae of five bivalve species under simulated power plant entrainment conditions: a synthesis

Upwelling effects of subsurface water on phytoplankton growth were evaluated by 9 simulated culture experiments of coastal upwelling. Particular attention was paid to the effects of nutrient enrichment on the surface phytoplankton by the upwelling of nutrient rich subsurface water and of the exposure of the subsurface phytoplankters to surface radiation. The following are the results obtained: the lag period of phytoplankton growth was inversely related to water temperature; the maximum yield of phytoplankton was proportional to the amounts of available initial nutrients; the specific growth rates of phytoplankton were a function of both the initial nutrient concentrations and water temperature; and the maximum specific growth rate was simply proportional to water temperature. According to the relations found, a simple equation is presented for the estimation of phytoplankton growth in a given upwelling. Succession of species in the phytoplankton assemblage in upwelled water mass was also taken into consideration.     

Smart Characterization—An Integrated Approach for Evaluating a Complex 1,4‐Dioxane Site

Smart characterization approaches apply the latest high‐resolution site characterization methods to find the contaminant mass flux, by integrating relative permeability mapping, classical hydrostratigraphy interpretation, and high‐density groundwater and saturated soil sampling. The key factor that makes Smart characterization different is the application of quantitative saturated soil sampling in less permeable slow advection and storage zones to diagnose plume maturity and understand its implications for remedy selection and performance. Because direct sensing tools like the membrane interface probe are capable of providing screening‐level assessments for hydrocarbons and chlorinated solvents in storage zones, but not 1,4‐dioxane, the recommended Smart approach involves application of specialized high‐capacity mobile laboratories or rapid turn‐around using fixed commercial labs. In addition to the benefit of rapidly characterizing sites, Smart characterization facilitates a flux‐based conceptual site model, which allows stakeholders to focus remedies on the mobile portion of the contaminant mass or, in effect, the mass that matters. Through systematic planning and implementation, predesign characterization can be completed to optimize source and plume remedy strategies, balancing investment in Smart characterization with reductions in total life‐cycle costs to ensure that an appropriate return on investigation is obtained.  © 2016 Wiley Periodicals, Inc.     

A Holistic Approach to Design Support for Bio-polymer Based Packaging

The growing interest in bio-polymers as a packaging material, particularly from companies looking to reduce their environmental footprint, has resulted in wider adoption. Traditionally the selection and specification of packaging materials was based on aesthetic, technical and financial factors, for which established metrics exist. However with bio-polymers, where the primary rationale for their use is environmental, alternative metrics are required. Furthermore, there is a significant strategic element to the decision process that requires a broader range of horizontal and vertical inputs, both within the business and the wider supply chain. It is therefore essential that a holistic approach is taken to the bio-polymer based packaging design process to ensure that the final packaging meets the original strategic intent and overall requirements of the business. Current eco-packaging design tools are generally limited to professional users, such as designers or packaging engineers, and generally provide tactical rather than strategic support. This disconnect, between the need for inclusivity and greater strategic support in holistic design, and the exclusivity and largely tactical support of current eco-design support tools, indicates a clear need for a new decision support tool for sustainable pack design using bio-polymers. This paper proposes a framework for an eco-design decision support tool for bio-polymer based packaging that has been developed using a predominantly qualitative research approach based on reviews, interviews and industrial packaging design experience and is an extension of previously published work. This research investigates further how existing eco-design methods, such as the ‘Balanced Score Card’, can be applied within the tool and how the shortcomings associated with incorporating social and environmental aspects can be partly resolved, through a simplified set of metrics tailored specifically for bio-polymer packaging decisions. The results of this research is a framework for the development of a three tier eco-design tool for bio-polymer packaging that provides decision support at the three critical stages of the design process: strategic fit, Feasibility assessment and concept/pack development.     

Interactions of Sulfur Dioxide with Insoluble Suspended Particulate Matter

A laboratory study was conducted of the heterogeneous catalysis of sulfur dioxide at ppm concentrations in air by insoluble particles of CaCO₂, V₂O₅, Fe₂0₃, flyash from a coal-burning power plant, MnCO₂, activated carbon, and suspended particulate matter from urban air. The investigalion was performed by utilizing a new technique for aerosol stabilization which consists of depositing the aerosol on Teflon beads in a fluidized bed. The Teflon beads with deposited aerosol particles were then packed into a flow reactor. Progress of the chemical reaction of SO₂ with deposited particles was continuously monitored by determining the SO₂ concentrations in the reactor effluent with a microcoulometer.

In this investigation, CaCOg, V₂O₅, and flyash were essentially inert to SO₂ at room temperature. Fe₂O₃, activated carbon, MnO₂, and suspended particulate matter from urban air sorbed SO₂ from air streams with up to 14.4 ppm SO₂ in air. Evidence is presented which suggests that a substantial part of the sorbed SO₂ was physically adsorbed.

Bioassay procedures which utilize pulmonary flow resistance changes in guinea pigs to monitor response to inhaled SO₂-aerosol mixtures in air have indicated the weak or non-potentiating capacity of insoluble aerosols as contrasted to soluble aerosols. Potentiating response of an aerosol appears to be strongly associated with reaction of SO₂ in a water droplet containing aerosol ions and not with physically adsorbed SO₂ on an insoluble aerosol.