Long-term assessment of efficacy of permeable pond covers for odour reduction

Three anaerobic ponds used to store and treat piggery wastes were fully covered with permeable materials manufactured from polypropylene geofabric, polyethylene shade cloth and supported straw. The covers were assessed in terms of efficacy in reducing odour emission rates over a 40-month period. Odour samples were collected from the surface of the covers, the surface of the exposed liquor and from the surface of an uncovered (control) pond at one of the piggeries. Relative to the emission rate of the exposed liquor at each pond, the polypropylene, shade cloth and straw covers reduced average emission rates by 76%, 69% and 66%, respectively. At the piggery with an uncovered control pond, the polypropylene covers reduced average odour emission rates by 50% and 41%, respectively. A plausible hypothesis, consistent with likely mechanisms for the odour reduction and the olfactometric method used to quantifying the efficacy of the covers, is offered.     

Assessment of permeable covers for odour reduction in piggery effluent ponds. 1. Laboratory-scale trials

A variety of materials were trialed as supported permeable covers using a series of laboratory-scale anaerobic digesters. Efficacy of cover performance was assessed in terms of impact on odour and greenhouse gas emission rate, and the characteristics of anaerobic liquor. Data were collected over a 12-month period. Initially the covers reduced the rate of odour emission 40-100 times relative to uncovered digesters. After about three months, this decreased to about a threefold reduction in odour emission rate, which was maintained over the remainder of the trial. The covers did not alter methane emission rates. Carbon dioxide emission rates varied according to cover type. Performance of the covers was attributed to the physical characteristics of the cover materials and changes in liquor composition. The reductions in odour emission indicate that these covers offer a cost-effective method for odour control.     

Odour emissions from anaerobic piggery ponds. 2: improving estimates of emission rate through recognition of spatial variability

Odour emission rates were measured for seven different anaerobic ponds treating piggery wastes at six to nine discrete locations across the surface of each pond on each sampling occasion over a thirteen month period. Significant variability in emission rates were observed for each pond. Measurement of a number of water quality variables in pond liquor samples collected at the same time and from the same locations as the odour samples indicated that the composition of the pond liquor was also variable. The results indicated that spatial variability was a real phenomenon and could have a significant impact on odour assessment practices. Considerably more odour samples would be required to characterise pond emissions than currently recommended by most practitioners, or regulatory agencies.     

Free—living fathead minnows rapidly learn to recognize pike as predators

Individuals from a natural population of approximately 20 000 fathead minnows from a pike–free pond did not respond with appropriate anti–predator behaviour upon encountering pike odour in laboratory tests. However, 14 days after 10 pike were stocked into the pond, minnows had acquired recognition of pike odour. Laboratory studies have indicated several possible mechanisms for acquiring predator recognition in fathead minnows. This study indicates that these, or similar processes, can produce major changes in predator recognition in the wild.     

Factors affecting the response of Ceutorhynchus assimilis Payk. (Col., Curculionidae) males to conspecific odour

The effect of post-emergence feeding on the response of Ceutorhynchus assimilis males to conspecific odour was studied using both laboratory-overwintered and field-collected weevils. The response of males to females at different times in the season was also investigated using field-collected weevils. Males did not respond to the odour of virgin females that were newly emerged from diapause. However, they showed a significant response to the odour of overwintered virgin females that had spent some days on flowering rape. The response of males to females appeared to decline as the season progressed.     

Broad-scale spatial patterns of canopy cover and pond morphology affect the structure of a Neotropical amphibian metacommunity

Spatial and environmental processes influence species composition at distinct scales. Previous studies suggested that the distribution of larval anurans at the landscape-scale is influenced by environmental gradients related to adult breeding site selection, such as pond canopy cover, but not by water chemistry. However, the combined effects of spatial, pond morphology, and water chemistry variables on metacommunity structure of larval anurans have not been analyzed yet. We used a partial redundancy analysis with variation partitioning to analyze the relative influence of pond morphology (e.g., depth, area, and aquatic vegetation), water chemistry, and spatial variables on a tadpole metacommunity from southeastern Brazil. We predict that pond morphology and canopy cover will influence the metacommunity at broad spatial scales, while water chemistry would play a larger role at finer scales. We found that broad-scale spatial patterns of pond canopy cover and pond morphology strongly influenced metacommunity structure, with water chemistry being not significant. Additionally, species composition was spatially autocorrelated at short distances. We suggest that the reproductive behavior of adult anurans is driving tadpole metacommunity dynamics, since pond morphology, but not water chemistry affects breeding site selection by adults. Our results contribute to the understanding of amphibian species diversity in tropical wetlands.     

A polymorphism of the ability to smell urinary metabolites of asparagus.

The urinary excretion of (an) odorous substance(s) after eating asparagus is not an inborn error of metabolism as has been supposed. The detection of the odour constitutes a specific smell hypersensitivity. Those who could smell the odour in their own urine could all smell it in the urine of anyone who had eaten asparagus, whether or not that person was able to smell it himself. Thresholds for detecting the odour appeared to be bimodal in distribution, with 10% of 307 subjects tested able to smell it at high dilutions, suggesting a genetically determined specific hypersensitivity.     

The orientation of walking honeybees in odour fields with small concentration gradients

The behaviour of walking honeybees in small gradient odour fields was investigated by means of a simulation technique. The bee was kept in one place by a locomotion compensator (‘running sphere’). This compensator allowed for a precise reconstruction of the bee's actual locomotion on the sphere, and presented the bee with a stimulating odour whose concentration was controlled by feedback from the reconstructed locomotion. This rendered possible the application of well-defined odour fields and revealed that: (1) honeybees are capable of finding odour sources in the absence of optical cues and with concentration gradients too small to allow tropotactic or klinotactic orientation; (2) bees are capable of memorizing odour concentrations with a high degree of accuracy; (3) this orientation system is based on a switching over from negative to positive anemotaxis at a ‘reference’ concentration; (4) this reference is a function of the odour concentration at which a sugar reward is given. The results do not support any hypothesis for an orientation system based on the detection and comparison of successive values of odour concentration. A hypothesis on the nature of the ‘reference value’ is discussed and supported by experiments.     

The influence of American mink odour on the spatial distribution and behaviour of water voles

The perception and assessment of predation risk often cause changes in the activities of animals and induce behavioural responses that may in turn affect their movements and distribution. To simulate high predation risk in a midfield pond riparian habitat, we used fresh faeces from ranch American mink Neovison vison and recorded behavioural responses of water voles Arvicola amphibius. In areas where mink odour was deployed, the numbers of captured vole individuals and their trappability were significantly lower than in control areas. Several voles migrated from the zones with deployed mink faeces to the areas without faeces, thus proving that increased predation risk affects the distribution of individuals in a population. The response to mink odour was much more pronounced in females than in males; in areas with deployed mink faeces, not a single female was trapped. We conclude that although American mink is a non‐native, invasive predator, water voles respond to mink odour by reducing their activity and/or by avoiding places with higher predation risk.     

Landfill methane oxidation in soil and bio-based cover systems: a review

Mitigation of landfill gases has gained the utmost importance in recent years due to the increase in methane (CH₄) emissions from landfills worldwide. This, in turn, can contribute to global warming and climatic changes. The concept of microbially mediated methane oxidation in landfill covers by using methanotrophic microorganisms has been widely adopted as a method to counter the rise in methane emissions. Traditionally, landfill soil covers were used to achieve methane oxidation, thereby reducing methane emissions. Meanwhile, the continual rise of CH₄ emissions from landfills and the significant need to and importance of developing a better technology has led researchers to explore different methods to enhance microbial methane oxidation by using organic rich materials such as compost in landfill covers. The development and field application of such bio-based systems, explored by various researches worldwide, eventually led to more widely accepted and better performing cover systems capable of reducing CH₄ emissions from landfills. However, the long-term performance of bio-based cover systems were found to be negatively affected by factors such as the material’s ability to self-degrade, causing CH₄ to be generated rather than oxidized as well as the greater potential for forming pore-clogging exopolymeric substances. In order to design an effective cover system for landfills, it is essential to have a thorough understanding of the concepts incorporated into methodologies currently in favor along with their pros and cons. This review summarizes previous laboratory and field-scale studies conducted on various soil and bio-based cover systems, along with the modeling mechanisms adopted for quantifying CH₄ oxidation rates. Finally, several issues and challenges in developing effective and economical soil and bio-based cover systems are presented.     

Microscopy with Plastic Substitutes for Cover Glasses

To determine whether plastic substitutes for cover glasses on microscope slides affect the performance of the microscope, their optical constants were determined. The plastic covers and glass cover glasses were mounted also on silvered slides to form Star Test Plates which were studied by competent observers. The thicker plastic cover glasses, now on the market, are satisfactory when mounted to give a plane surface. Optically inhomogeneous materials, of irregular thickness, those that curl or do not have plane surfaces, adversely affect the performance of the microscope and should not be used. Since the substitutes are softer than glass they must be protected from abrasion. It is recommended that thicknesses of 0.18 mm., and none outside of a range of 0.12 to 0.20 mm. be used. For critical observation with unimmersed objectives of high aperture, best results are obtained with the correction collar set at the position corresponding to the actual thickness of the cover slip, just as would be done with glass cover glasses.     

Contingencies in the behaviour of the crab Heterozius rotundifrons

We recorded the responses of individual intertidal crabs, Heterozius rotundifrons, to stimuli presented singly and in combinations in the laboratory. Undisturbed crabs did not respond to the introduction of odour from a crushed conspecific but did respond strongly to food odour. Undisturbed crabs responded equally to food odour alone and a combination of food and odour from a crushed conspecific. When tactile stimulation was applied, as when the crab is grasped by a predator, individual H. rotunidfrons assumed a rigid, appendage-extended posture for several minutes. Tests with predatory fish showed that this catatonic posture is a very effective predator-defence mechanism. The duration of the catatonic state was decreased by the addition of food odour but increased by the addition of alarm odour (crushed conspecific) or the combination of alarm and food odours. Thus, which chemical stimulus was dominant was reversed by tactile input (i.e. dominance was contingent upon context). The effect of alarm odour on food odour responses lasted 4 h. Visual input in the form of a shadow passing over the crabs, either before or after tactile induction of the catatonic state, also increased the duration of that state. However, the duration of the catatonic state following exposure to both cues associated with danger (shadow+alarm odour) was similar to that of the control level. The crabs appeared to switch strategies when three cues associated with danger (tactile grasping, alarm odour and shadows) were detected, either simultaneously or over a 4-h period. The results illustrate the highly contingent nature of the behaviour of these crabs. Copyright 2000 The Association for the Study of Animal Behaviour.     

CULEX ANNULIROSTRIS SKUSE (DIPTERA: CULICIDAE) AT APPIN, N. S. W.—BIONOMICS AND BEHAVIOUR

Abstract
Larval and adult populations of Culex annulirostris were sampled for two years. Populations appeared in pond samples and dry-ice baited light traps in Oct, increased into mid summer, then disappeared in May. Larval populations appeared to reflect rainfall which promoted oviposition. The species overwintered as a female population that was predominantly parous. Females were more attracted to chickens than to guinea pigs. There was no evidence of autogeny in the population. The duration of the gonotrophic cycle ranged from 4 to 12 days depending on temperature. Females old enough to transmit arboviruses were present from Oct to May.     

Pilot-scale semisolid fermentation of straw.

Semisolid fermentation of ryegrass straw to increase its animal feed value was successfully performed on a pilot scale. The pilot plant, which could handle 100 kg of straw per batch, was designed so that all major operations could take place in one vessel. The straw was hydrolyzed at 121 degrees C for 30 min with 0.5 N H2SO4 (7:3 liquid:solid), treated with ammonia to raise the pH to 5.0, inoculated with Candida utilis, and fermented in a semisolid state (70% moisture). During fermentation the straw was held stationary with air blown up through it. Batch fermentation times were 12 to 29 h. Semisolid fermentation did not require agitation and supported abundant growth at 20 to 40 degrees C even at near zero oxygen tensions. Fermentation increased the protein content, crude fat content, and in vitro rumen digestibility of the straw.     

Arrestment responses of the predatory mite, Phytoseiulus persimilis, to steep odour gradients of a kairomone

ABSTRACT. The response of the predatory mite, Phytoseiulus persimilis Athias-Henriot, to steep gradients of a volatile kairomone emitted by its prey, Tetranychus urticue Koch, was studied in a vertical air flow chamber. The orientation to wind direction was eliminated by using an olfactometer that had an air stream approaching the predator from below a gauze screen upon which the predator walked. The steep gradient of odour was obtained by putting a cylinder filled with prey-infested leaves vertically below the screen. Starved predators were arrested in the odour patch by walking more slowly and tortuously than well-fed predators. The latter mites did not show a significant ortho- or klinokinetic response to the presence of odour. Both well-fed and starved predators showed a chemotactic response to steep gradients at the border of the circular odour patch. Predators that happened to walk out of the patch, frequently turned back to it. This response is presumably based on idiothetic information about the predator's immediately previous walking directions, because it occurred in the odour-free zone after passing the steep gradient of prey odour. Right-about turns can help the predator to stay in static odour plumes with steep gradients at the borders. This type of plume is present only close to the odour source. Further away from the source the odour plume tends to move to and fro due to variation in wind direction. For the predator to keep track of these snaking plumes the right-about turns are unlikely to be of any value because the response is of short duration and because the response to a moving plume appeared to be inadequate; by moving the cylinder below the screen (and consequently the odour patch) it was found that the predator turned back even if the odour gradient was made to pass the predator in the same direction as that of the predator's movement.     

Small area and low connectivity constrain the diversity of plant life strategies in temporary ponds

Aim

(i) To determine whether area and connectivity of temporary ponds can predict plant species diversity, and the diversity and abundance of different plant life histories; (ii) To explore whether pond connectivity with the river prior to river regulation predicts better plant diversity patterns than current pond connectivity, suggestive of possible effects of connectivity loss.

Location

Eastern Carpathian Mountains, Romania, Europe.

Methods

We fitted linear and generalized linear models (LM and GLM) to examine whether pond area and current distance from the Olt River predict plant species richness, Shannon diversity and relative cover of different social behaviour types and overall plant species richness and Shannon diversity. Using historical maps, we measured pond distance from the river ca. 60 years before the Olt River was regulated, and we refitted the LM and GLM models using pond area and past distance from the river as independent variables.

Results

Total plant species richness increased with pond area, and it decreased with the distance from the river, but total plant Shannon diversity index was affected, positively, only by pond area. The strength of responses to pond area and connectivity of species richness, Shannon diversity and relative cover varied across the different social behaviour types. Past and current distances between ponds and riverbeds had similar effects on plant diversity, with some evidence for stronger effect of the present connectivity on specialist species Shannon diversity and a weaker effect on disturbance tolerants, generalists and competitors.

Main Conclusions

Pond area and connectivity with the landscape are important predictors of the diversity of plant life history strategies, and therefore, useful tools in pond conservation. Consistent species richness and Shannon diversity responses of wetland specialists to pond area and connectivity make this life history type well suited for monitoring pond condition.     

Breeding and egg survival of a population of a salamander,Hynobius nebulosus tokyoensis Tago

1. A population of a salamander, Hynobius nebulosus tokyoensisTago was studied at Habu, Hinodemachi, in Tokyo during the breeding seasons from 1976 to 1978. Adults appeared in the pond were captured and marked individually by toe-clipping. Egg sacks were counted and tagged with vinyl tapes for the marking.
2. The annual egg production of this population was found to be constant, about 6500 eggs, and total number of breeding adults appeared in the pond also varied little during three years.
3. The appearance of breeding adults in the pond and oviposition seemed to be influenced by the rise of temperature and rainfall.
4. Males appeared earlier in the pond and stayed there for approximately 10 to 20 days. On the other hand, females appeared later in the pond and left there soon after laying eggs.
5. Mean clutch size and body length of breeding adults appeared in the pond showed a tendency to decrease as time proceeded, which seemed to show that the smaller and younger the salamander was, the later it appeared in the pond.
6. Owing to low temperature, the eggs laid earlier took more time to hatch than those laid later.
7. The survival rate of eggs was 67.2% in 1976, 86.4% in 1977 and 81.2% in 1978. The loss rate of eggs laid in the early and late periods of oviposition was higher than that of eggs laid in the middle period.

     

Uncoupling physical and chemical cues: The independent roles of scale cover size and kairomone concentration on host selection byAphytis melinus DeBach (Hymenoptera: Aphelinidae)

The ectoparasitoidAphytis melinus initially selects its host, California red scale,Aonidiella aurantii (Maskell) (Homoptera: Diaspididae), using characteristics of the host’s cover before assessing the quality of the scale body beneath. Host suitability is known to increase with host size until the scale insect reaches maturity, after which it is no longer available for parasitism. The wasp uses a combination of scale cover size and a kairomone,O-caffeoyltyrosine, in the cover for initial assessment. Under natural conditions these two factors are frequently coupled. We quantified the relative importance of cover size and kairomone concentration independently by removing and selectively reapplying controlled doses of syntheticO-caffeoyltyrosine to scale covers of known size. In the absence of the kairomone, wasps did not discriminate among scale covers differing in size. Wasps showed a curvilinear response to kairomone dose for each scale cover age group. Wasps preferred low doses ofO-caffeoyltyrosine on young, small scale covers, and high doses on old, large scale covers. The ability of wasps to respond quantitatively to the kairomone may be used in the field to differentiate small second-instar from larger and more suitable third-instar scale insect larvae.     

Kin recognition in the ant Rhytidoponera confusa II. Gestalt odour

Two models have been proposed for the transfer of genetically determined colony odour pheromones in social insects. The ‘Gestalt’ model suggests a complete transfer of pheromones amongst all nestmates whereas the ‘Individualistic’ model suggests no significant odour transfer with nestmates bearing individually distinct odours. In experiments with the ant Rhytidoponera confusa, colonies showed significantly more aggression (12% aggression) towards nestmates that had been kept in cages with non-nestmates than they did to nestmate controls (0% aggression). Colonies also showed significantly less aggression against non-nestmates that had been kept with nestmates in a separate cage (84% aggression) than they did to non-nestmate controls (100% aggression). A second experiment indicated that workers can absorb colony-specific odours from the nest materials of other colonies. However, whilst both experiments indicated a partial Gestalt component to the colony odour (ca. 28%), the Individualistic component seemed to be more important (ca. 72%).     

Effects of fish density on planktonic communities and water quality in a manipulated forest pond

We examined the effects of fish on lower trophic levels in a small pond in eastern Finland. The pond was divided into four sections with plastic curtains and stocked with crucian carp (Carassius carassius); two sections had low (4.4–5.5 g m^–3) and two high (10.4–13.7 g m^–3) densities of fish. In the summer of 1987, the pond was sampled weekly for phyto- and zooplankton until the fish were removed by rotenone in September after a three month experiment. Fish density as well as the extent of macrophyte cover had a considerable impact on planktonic communities and water quality. Mean zooplankton biomass was significantly lower and phytoplankton biomass higher, at high fish density. Water transparency was correlated negatively with chlorophyll-a at low fish density but turbidity appeared to reduce transparency at high fish density. The composition and dynamics of the plankton also differed at different fish densities. The mechanisms behind these effects, and the influences of habitat and fish behaviour on the results, are discussed.