Strategic male signalling effort in a desert-dwelling fish

Males often use elaborate courtship displays to attract females for mating. Much attention, in this regard, has been focused on trying to understand the causes and consequences of signal variation among males. Far less, by contrast, is known about within-individual variation in signal expression and, in particular, the extent to which males may be able to strategically adjust their signalling output to try to maximise their reproductive returns. Here, we experimentally investigated male courtship effort in a fish, the Australian desert goby, Chlamydogobius eremius. When offered a simultaneous choice between a large and a small female, male gobies spent significantly more time associating with, and courting, the former, probably because larger females are also more fecund. Male signalling patterns were also investigated under a sequential choice scenario, with females presented one at a time. When first offered a female, male courtship was not affected by female size. However, males adjusted their courtship effort towards a second female depending on the size of the female encountered previously. In particular, males that were first offered a large female significantly reduced their courtship effort when presented with a subsequent, smaller, female. Our findings suggest that males may be able to respond adaptively to differences in female quality, and strategically adjust their signalling effort accordingly.     

Does Tephrosia candida as fallow species, hedgerow or mulch improve nutrient cycling and prevent nutrient losses by erosion on slopes in northern Viet Nam?

Agroforestry is considered to be a promising alternative to short-fallow shifting cultivation or other monocropping systems. An on-farm experiment was established in 1996 in northern Viet Nam to examine the contribution of the leguminous bush Tephrosia candida (Roxb.) D.C. as a fallow or hedgerow species and as a mulch producer to improve nutrient cycling and prevent nutrient losses by erosion. The systems tested were upland rice monocropping (Mono), natural fallow (NaFa), fallow of Tephrosia (TepFa), hedgerow intercropping with upland rice (Oryza sativa L.) and internal mulching using pruned Tephrosia biomass (TepAl), and upland rice with external mulching using Tephrosia biomass (TepMu). Over two cropping seasons, from April 1996 to April 1998, nutrients recycled and inputs and exports were recorded, as well as changes in C-, N- and P-pools, and in pH in the 0–5 cm topsoil layer.The Tephrosia systems (TepFa, TepAl, TepMu) prevented nutrient losses by erosion effectively. Compared to the NaFa system, the TepFa system accumulated 34% more N in the above-ground plant parts and increased topsoil N by 20%, probably due to N-fixation. There was a trend that the less labile P-pools (NaOH-P) were reallocated into the more labile P-pools (Bicarb-P) in the soil of the TepFa system. Burning released significant amounts of the inorganic P-pools in both the NaFa and TepFa systems and this effect seemed to be more pronounced in the TepFa than in the NaFa. Organic input to crop export ratios for N and P were >1 in the TepAl and TepMu treatments. This was due to a sufficient quantity and quality of the Tephrosia mulching material. However, moderately labile NaOH-extractable organic P seemed to be depleted in the topsoil due to high P uptake in the TepMu treatment. Thus, nutrient cycling and nutrient balances were improved under the Tephrosia systems. But for long-term P sustainability, there is a belief that a combined use of mulching and mineral P fertiliser is needed.     

Natural formation and degradation of chloroacetic acids and volatile organochlorines in forest soil--challenges to understanding

- DOI: http:/dx.doi.org/10.1065/espr2005.06.262 Goal, Scope and Background The anthropogenic environmental emissions of chloroacetic acids and volatile organochlorines have been under scrutiny in recent years because the two compound groups are suspected to contribute to forest dieback and stratospheric ozone destruction, respectively. The two organochlorine groups are linked because the atmospheric photochemical oxidation of some volatile organochlorine compounds is one source of phytotoxic chloroacetic acids in the environment. Moreover, both groups are produced in higher amounts by natural chlorination of organic matter, e.g. by soil microorganisms, marine macroalgae and salt lake bacteria, and show similar metabolism pathways. Elucidating the origin and fate of these organohalogens is necessary to implement actions to counteract environmental problems caused by these compounds. Main Features While the anthropogenic sources of chloroacetic acids and volatile organochlorines are relatively well-known and within human control, knowledge of relevant natural processes is scarce and fragmented. This article reviews current knowledge on natural formation and degradation processes of chloroacetic acids and volatile organochlorines in forest soils, with particular emphasis on processes in the rhizosphere, and discusses future studies necessary to understand the role of forest soils in the formation and degradation of these compounds. Results and Discussion Reviewing the present knowledge of the natural formation and degradation processes of chloroacetic acids and volatile organochlorines in forest soil has revealed gaps in knowledge regarding the actual mechanisms behind these processes. In particular, there remains insufficient quantification of reliable budgets and rates of formation and degradation of chloroacetic acids and volatile organochlorines in forest soil (both biotic and abiotic processes) to evaluate the strength of forest ecosystems regarding the emission and uptake of chloroacetic acids and volatile organochlorines, both on a regional scale and on a global scale. Conclusion It is concluded that the overall role of forest soil as a source and/or sink for chloroacetic acids and volatile organochlorines is still unclear; the available laboratory and field data reveal only bits of the puzzle. Detailed knowledge of the natural degradation and formation processes in forest soil is important to evaluate the strength of forest ecosystems for the emission and uptake of chloroacetic acids and volatile organochlorines, both on a regional scale and on a global scale. Recommendation and Perspective As the natural formation and degradation processes of chloroacetic acids and volatile organochlorines in forest soil can be influenced by human activities, evaluation of the extent of this influence will help to identify what future actions are needed to reduce human influences and thus prevent further damage to the environment and to human health caused by these compounds.     

Improving marine water quality by mussel farming: a profitable solution for Swedish society

Eutrophication of coastal waters is a serious environmental problem with high costs for society globally. In eastern Skagerrak, reductions in eutrophication are planned through reduction of nitrogen inputs, but it is unclear how this can be achieved. One possible method is the cultivation of filter-feeding organisms, such as blue mussels, which remove nitrogen while generating seafood, fodder and agricultural fertilizer, thus recycling nutrients from sea to land. The expected effect of mussel farming on nitrogen cycling was modeled for the Gullmar Fjord on the Swedish west coast and it is shown that the net transport of nitrogen (sum of dissolved and particulate) at the fjord mouth was reduced by 20%. Existing commercial mussel farms already perform this service for free, but the benefits to society could be far greater. We suggest that rather than paying mussel farmers for their work that nutrient trading systems are introduced to improve coastal waters. In this context an alternative to nitrogen reduction in the sewage treatment plant in Lysekil community through mussel farming is presented. Accumulation of bio-toxins has been identified as the largest impediment to further expansion of commercial mussel farming in Sweden, but the problem seems to be manageable through new techniques and management strategies. On the basis of existing and potential regulations and payments, possible win-win solutions are suggested.     

Effects of whole spine alignment patterns on neck responses in rear end impact

Objective: The aim of this study was to investigate the whole spine alignment in automotive seated postures for both genders and the effects of the spinal alignment patterns on cervical vertebral motion in rear impact using a human finite element (FE) model.

Methods: Image data for 8 female and 7 male subjects in a seated posture acquired by an upright open magnetic resonance imaging (MRI) system were utilized. Spinal alignment was determined from the centers of the vertebrae and average spinal alignment patterns for both genders were estimated by multidimensional scaling (MDS). An occupant FE model of female average size (162 cm, 62 kg; the AF 50 size model) was developed by scaling THUMS AF 05. The average spinal alignment pattern for females was implemented in the model, and model validation was made with respect to female volunteer sled test data from rear end impacts. Thereafter, the average spinal alignment pattern for males and representative spinal alignments for all subjects were implemented in the validated female model, and additional FE simulations of the sled test were conducted to investigate effects of spinal alignment patterns on cervical vertebral motion.

Results: The estimated average spinal alignment pattern was slight kyphotic, or almost straight cervical and less-kyphotic thoracic spine for the females and lordotic cervical and more pronounced kyphotic thoracic spine for the males. The AF 50 size model with the female average spinal alignment exhibited spine straightening from upper thoracic vertebra level and showed larger intervertebral angular displacements in the cervical spine than the one with the male average spinal alignment.

Conclusions: The cervical spine alignment is continuous with the thoracic spine, and a trend of the relationship between cervical spine and thoracic spinal alignment was shown in this study. Simulation results suggested that variations in thoracic spinal alignment had a potential impact on cervical spine motion as well as cervical spinal alignment in rear end impact condition.     

Mate choice,fecundity and sexual dimorphism in two pipefish species (Syngnathidae)

Summary In order to understand the causes of sexual dimorphism, mate choice and size-related fecundity were studied in two pipefish species, Syngnathus typhle and Nerophis ophidion. Sexual dimorphism is more pronounced in N. ophidion; females are larger, have sexual colourings, and are more active during courtship. In S. typhle the sexes are alike in all these respects. Males brood their offspring in both species. In N. ophidion fecundity was positively correlated with both body size and the amount of sexual colouring in females. In males no correlation between body size and fecundity, or between body size and embryo size existed. Predictably, in mate choice experiments with equal-sized females, males chose females with more extensive sexual colourings. We explain sexual dimorphism in this species as a consequence of both natural selection (fecundity increases with size in females but not in males) and sexual selection (males prefer larger females). We argue that sexual size dimorphism did not evolve by selection minimizing overlap in food niches between the sexes, because food production is high in the Zostera beds where the fishes live, and no size dimorphism was found in the sympatrically occurring S. typhle. Furthermore, in N. ophidion dimorphism is not greater in a particular mouth character than in overall body size. In S. typhle egg size and the average number of eggs transferred per spawning were positively correlated with female body size. Apparently more energy per offspring was provided by larger males than by smaller males, and larger males also carried more offspring. As predicted, large mates were preferred by both sexes in mate choice experiments. This is explicable in terms of both natural selection (fecundity increases with size in both sexes) and sexual selection (both sexes prefer large mates). As a consequence of selection acting in the same direction in both sexes, sexual dimorphism is absent in S. typhle.     

High Spatial and Temporal Variability of Dry Deposition in a Coastal Region

A real meteorological situation characterized by strong spatial and temporal variability of the meteorological fields in a coastal region of eastern Denmark is examined in view of the transport of a passive tracer and dry deposition. Model simulations using a full mesoscale NWP model (COAMPS^TM) at different horizontal resolutions are performed. A realistic simulation showed that the differences in the amount of dry deposited matter can reach one order of magnitude and larger, during the period of one afternoon, depending on the model horizontal resolution. In addition, the results of an idealized experiment with straight coastline indicate that the horizontal model resolution alone is responsible for most of the differences. This study confirms the importance of high spatial and temporal resolution modelling for environmental applications.     

Environment-specific elasticity and sensitivity analysis of the stochastic growth rate

For matrix population models, analyses of how sensitive the population growth rate is to changes in vital rates (i.e. perturbations) are important for studies of life history evolution as well as for management and conservation of threatened species. There are two types of sensitivity analyses corresponding to absolute (sensitivity) or relative (elasticity) changes in the vital rates and both types can be applied to both deterministic and stochastic matrix population models. To date, most empirical studies of elasticity and sensitivity of the stochastic growth rate have examined the response to perturbations in the vital rates in a complete set of possible environments. However, it is often of interest to examine the response to perturbations occurring in only a subset of the possible environments. This has been done for periodic time-varying models elsewhere, but here we describe a recently published method for calculating the environment-specific sensitivity and elasticity of the stochastic growth rate and apply this method to data. These environment-specific perturbation analyses provide a logical way of dividing the sensitivity and elasticity among the environments. They give important insight into the selection regime in different environments and can provide valuable information for making management decisions and management evaluations in stochastic environments.     

GREENING FOOD PROCESSING INDUSTRIES IN VIETNAM: OPPORTUNITIES AND CONSTRAINTS

The food processing sector in Vietnam plays a vital role in its economic development, but its rapid growth seems to go hand-in-hand with environmental deterioration. Several decades of applying the conventional end-of-pipe approach made clear that it only deals with treating the symptoms. It is necessary to combine technological (end-of-pipe) solutions to overcome urgent pollution problems with ways to prevent wastes from being generated or to reuse their valuable material. This article presents a methodology for analyzing the possibilities for waste prevention in food processing industry in Vietnam.     

The interval between sexual encounters affects male courtship tactics in a desert-dwelling fish

Courtship displays are often important in determining male mating success but can also be costly. Thus, instead of courting females indiscriminately, males might be expected to adjust their signalling effort strategically. Theory, however, predicts that such adjustments should depend on the rate with which males encounter females, a prediction that has been subject to very little empirical testing. Here, we investigate the effects of female encounter rate on male courtship intensity by manipulating the time interval between sequential presentations of large (high quality) and small (low quality) females in a fish, the Australian desert goby Chlamydogobius eremius. Males that were presented with a small female immediately after a large female reduced their courtship intensity significantly. However, males courted large and small females with equal intensity if the interval between the sequential presentations was longer. Our results suggest that mate encounter rate is an important factor shaping male reproductive decisions and, consequently, the evolutionary potential of sexual selection.