The relationship between dewlap size and performance changes with age and sex in a Green Anole (Anolis carolinensis) lizard population

Ornaments are believed to signal an individual's ability to reproduce successfully and/or survive. Since an individual's fitness is often influenced by multiple traits (e.g. number of copulations, ability to acquire nest sites or to escape predators), which are difficult to quantify simultaneously, we examine performance traits (bite force, jumping performance) believed to be relevant to an individual's fitness. Specifically, we ask whether variation in dewlap size is related to variation in body size, bite force and jumping ability in the lizard Anolis carolinensis. Our results show that dewlap size is correlated with jumping capacity across all individuals, whereas the relationships between dewlap size, body size and bite force differ depending on sex/age class. We argue that selection against relatively large dewlaps at the transition between small mature and large mature males might be responsible for the lack of a relationship within large males. The absence or presence of a correlation between dewlap size and bite force, on the other hand, might be explained by differences in behaviour, such as territory establishment, anti-predator tactics, and/or mate choice. Our work thus suggests that selective forces influencing the evolution of ornaments may operate differently on different sexes and life-history stages.     

Mussels flexing their muscles: a new method for quantifying bivalve behaviour

We employed a novel technique to quantify how blue mussels Mytilus edulis react to predation risk in their environment by quantifying mussel gape using a Hall sensor attached to one shell valve reacting to a magnet attached to the other. Change in gape angle per second (CHIGA) versus gape angle plots resulted in a distribution with a boundary, which defined the maximum CHIGA of a mussel at all gape angles. CHIGA boundary plots for all individual mussels were similar in form. However, the CHIGA boundary increased in extent with mussel length (maximum CHIGA for mussel valve closures for mussels 2.98 and 79.6 mm long were −1.5 and −11°s⁻¹, respectively), showing that larger mussels opened and closed most rapidly. Mussel extract added to the seawater, a factor believed to signal predation, caused mussels to close significantly faster than otherwise (P < 0.001). This approach for assessing how mussels react to their environment indicates that mussel response to predation is graded and complex and may well indicate animal-based assessments of the trade-off between effective feeding and the likelihood of predation.     

Should managed populations be monitored every year?

We often need to estimate the size of wild populations to determine the appropriate management action, for example, to set a harvest quota. Monitoring is usually planned under the assumption that it must be carried out at fixed intervals in time, typically annually, before the harvest quota is set. However, monitoring can be very expensive, and we should weigh the cost of monitoring against the improvement that it makes in decision making. A less costly alternative to monitoring annually is to predict the population size using a population model and information from previous surveys. In this paper, the problem of monitoring frequency is posed within a decision-theory framework. We discover that a monitoring regime that varies according to the state of the system can outperform fixed-interval monitoring. This idea is illustrated using data for a red kangaroo (Macropus rufus) population in South Australia. Whether or not one should monitor in a given year is dependent on the estimated population density in the previous year, the uncertainty in that population estimate, and past rainfall. We discover that monitoring is important when a model-based prediction of population density is very uncertain. This may occur if monitoring has not taken place for several years, or if rainfall has been above average. Monitoring is also important when prior information suggests that the population is near a critical threshold in population abundance. However, monitoring is less important when the optimal management action would not be altered by new information.     

Upstream Turbulence Effect on Pollution Dispersion

Experiments have been carried out to investigate turbulence at and above roof-level in an urban environment, and to predict the behaviour of street pollution from experiments using dye dispersion, for different roughness conditions and bed geometries. The flow in the boundary layer above an idealised urban environment has been simulated in a laboratory water flume. Comparisons have been made for the same model street canyon with and without the presence of upstream roughness. In the tests reported here, model street canyons were aligned perpendicular to the flow direction, and velocity measurements made within and above the model street canyons using a laser Doppler velocimeter (LDV). Flow visualisation techniques have also been used to confirm the gross flow features from streak images. Turbulence generated from the upstream roughness has a significant effect on the turbulence production and dispersion behaviour of the dye simulating pollution in street canyons.     

A gas-phase biosensor for environmental monitoring of formic acid: laboratory and field validation

In order to encourage more exposure measurements to be performed, a formic acid gas-phase biosensor has been developed for this purpose. In the present paper, an enzyme based biosensor has been validated with respect to analyte selectivity and on-site use. To ensure that the sampler developed measures the compound of interest the biosensor was exposed to three near structural homologues to formic acid, i.e. acetic acid, methanol and formaldehyde. These vapours were generated with and without formic acid and the only compound that was found to have an effect on the performance of the biosensor, albeit a small one, was acetic acid. The field test was performed in a factory using formic acid-containing glue for glulam products. In parallel to the measurements with the biosensor a well defined reference method was used for sampling and analysing formic acid. It was found that the biosensor worked satisfactorily in this environment when used in a stationary position. It was also shown that the biosensor could determine formic acid vapour concentrations down to 0.03 mg m(-3).     

Quantitative PCR Detection and Characterisation of Human Adenovirus,Rotavirus and Hepatitis A Virus in Discharged Effluents of Two Wastewater Treatment Facilities in the Eastern Cape,South Africa

The occurrence of enteric viruses in reclaimed wastewater, their removal by efficient treatment processes and the public health hazards associated with their release into the environments are of great significance in environmental microbiology. In this study, TaqMan-based real-time polymerase chain reaction (qPCR) was used to assess the prevalence of human adenovirus (HAdV), rotavirus (RV) and hepatitis A virus (HAV) in the final effluents of two wastewater treatment plants in the Eastern Cape Province, South Africa, over a twelve-month sampling period. The correlation between the concentrations of viruses in the effluents samples and faecal coliform (FC) densities were assessed as to validate the use of FC as microbiological indicator in water quality assessment. HAdV was detected in 62.5 % (30/48) of the samples with concentrations ranging between 8.4 × 10¹ and 1.0 × 10⁵ genome copies/L while HAV and RV were only detected at concentrations below the set detection limits. FCs densities ranged from 1 to 2.7 × 10⁴ CFU/100 ml. Adenovirus species HAdV-B (serotype 2) and HAdV-F (serotype 41) were detected in 86.7 % (26/30) and 6.7 % (2/30) of the HAdV-positive samples, respectively. No consistent seasonal trend was observed in HAdV concentrations, however, increased concentrations of HAdV were generally observed in the winter months. Also, there was no correlation between the occurrence of HAdV and FC at both the treatment plants. The persistent occurrence of HAdV in the discharged treated effluents points to the potential public health risk through the release of HAdV into the receiving watersheds, and the possibility of their transmission to human population.