Behavioural and Physiological Effects of Finely Balanced Decision-Making in Chickens

In humans, more difficult decisions result in behavioural and physiological changes suggestive of increased arousal, but little is known about the effect of decision difficulty in other species. A difficult decision can have a number of characteristics; we aimed to monitor how finely balanced decisions, compared to unbalanced ones, affected the behaviour and physiology of chickens. An unbalanced decision was one in which the two options were of unequal net value (1 (Q1) vs. 6 (Q6) pieces of sweetcorn with no cost associated with either option); a finely balanced decision was one in which the options were of equal net value (i.e. hens were "indifferent" to both options). To identify hens'' indifference, a titration procedure was used in which a cost (electromagnetic weight on an access door) was applied to the Q6 option, to find the individual point at which hens chose this option approximately equally to Q1 via a non-weighted door. We then compared behavioural and physiological indicators of arousal (head movements, latency to choose, heart-rate variability and surface body temperature) when chickens made decisions that were unbalanced or finely balanced. Significant physiological (heart-rate variability) and behavioural (latency to pen) differences were found between the finely balanced and balanced conditions, but these were likely to be artefacts of the greater time and effort required to push through the weighted doors. No other behavioural and physiological measures were significantly different between the decision categories. We suggest that more information is needed on when best to monitor likely changes in arousal during decision-making and that future studies should consider decisions defined as difficult in other ways.     

Regional and Landscape-scale Patterns of Shrub Invasion in Tropical Savannas

The shrubby vine Cryptostegia grandiflora and the shrub Ziziphus mauritiana were both introduced to northern Australia over 100 years ago and have become invasive in savanna woodland environments. Data from a land resource survey were used to examine regional- and landscape-scale distribution patterns of these species in the Dalrymple Shire, an area of over 6 1/2 million hectares in northeast Queensland. Each species was present at 10% of the 2362 sites examined and most frequent and abundant close to Charters Towers, the major settlement of the regions. C. grandiflora was recorded at 50 % of sites within 20 km of the town and in 14 out of 21 of the region's major sub-catchments. Z. mauritiana was recorded at 32 % of sites within 20km of Charters Towers, but in only three sub-catchments. Little of the variation in frequency and abundance of C. grandiflora and Z. mauritiana was accounted for by landscape factors, including geology, soils, or vegetation. While survey results do not absolutely distinguish between history, habitat and disturbance in explaining the weed's current distributions within the region, a strong influence of historical factors is suggested. Both exotic species were much less abundant than Carissa spp., a native taxon that has purportedly increased in the region in recent decades. In spite of their current prominence as weeds, there is potential for further increase by both C. grandiflora and Z. mauritiana. This increase could include expansion from the zone of high abundance and proliferation within that zone. While the results of such surveys must be interpreted with caution, they can yield useful information about regional patterns of plant invasion.     

Energy conservation characterizes sleep in sharks

Sharks represent the earliest group of jawed vertebrates and as such, they may provide original insight for understanding the evolution of sleep in more derived animals. Unfortunately, beyond a single behavioural investigation, very little is known about sleep in these ancient predators. As such, recordings of physiological indicators of sleep in sharks have never been reported. Reduced energy expenditure arising from sustained restfulness and lowered metabolic rate during sleep have given rise to the hypothesis that sleep plays an important role for energy conservation. To determine whether this idea applies also to sharks, we compared metabolic rates of draughtsboard sharks (Cephaloscyllium isabellum) during periods ostensibly thought to be sleep, along with restful and actively swimming sharks across a 24 h period. We also investigated behaviours that often characterize sleep in other animals, including eye closure and postural recumbency, to establish relationships between physiology and behaviour. Overall, lower metabolic rate and a flat body posture reflect sleep in draughtsboard sharks, whereas eye closure is a poorer indication of sleep. Our results support the idea for the conservation of energy as a function of sleep in these basal vertebrates.     

Spectrophotometric determination of polar and non-polar lipids in oleaginous yeast

A spectrophotometric method of determining extractable lipids was compared with a gravimetric method to estimate intracellular polar and non-polar lipids in the oleaginous yeast, Candida curvata. The methods correlated well but the spectrophotometric method was simpler, required less sample, and its accuracy was not affected by non-lipid components.L.W. Wang, D. Radford and K.Y. Cho are with the Microbiology Department, University of Sydney, NSW 2006, Australia. N.G. Nair is with NSW Agriculture, Rydalmere, NSW 2116, Australia.     

Residues of brodifacoum and other anticoagulant pesticides in target and non‐target species,Nelson Lakes National Park,New Zealand

Abstract

Cereal‐based bait containing 20 ppm brodifacoum was used in bait stations continuously from December 1997 to August 2000 in the Rotoiti Nature Recovery Project area, for controlling brushtail possum (Trichosurus vulpecula), ship rat (Rattus rattus), and house mouse (Mus musculus) populations. Concurrently (and before and after), baits containing brodifacoum, bromadiolone, flocoumafen, coumatetralyl, or warfarin were also used in St Arnaud village and on farms immediately adjacent to the project area. Brodifacoum residues were detected in the livers of 234 mammals from eight species, and two birds from two species captured alive, and a further seven birds from five species found dead in the project area (cause of death unknown). The highest concentration of brodifacoum residues in mammalian livers was recorded during the period brodifacoum was used in the project area. However, residues were present in the livers of some individuals at least 24 months after brodifacoum use in the project area stopped. These residues may have persisted in animals surviving brodifacoum use in the project area, and/or been transported into the area by animals moving to and from the adjacent village and farms, where brodifacoum use continued. Residues of flocoumafen, coumatetralyl, or warfarin, used only in the village and on farms, were also detected in the livers of animals captured up to at least 8 km from the nearest source. The results concur with other studies cautioning against indiscriminate or prolonged use of persistent anticoagulants for vertebrate pest control. However, the risks from such pesticides must be balanced against the demonstrable benefits of reducing pest abundance.     

Bargaining babblers: vocal negotiation of cooperative behaviour in a social bird

Wherever individuals perform cooperative behaviours, each should be selected to adjust their own current contributions in relation to the likely future contributions of their collaborators. Here, we use the sentinel system of pied babblers (Turdoides bicolor) to show that individuals anticipate contributions by group mates, adjusting their own contribution in response to information about internal state broadcast by others. Specifically, we show that (i) short-term changes in state influence contributions to a cooperative behaviour, (ii) individuals communicate short-term changes in state, and (iii) individuals use information about the state of group mates to adjust their own investment in sentinel behaviour. Our results demonstrate that individual decisions about contributions to a cooperative effort can be influenced by information about the likely future contribution of others. We suggest that similar pre-emptive adjustments based on information obtained from collaborators will be a common feature of cooperative behaviour, and may play an important role in the development of complex communication in social species.     

Production of15N-labelled hen egg white lysozyme usingAspergillus niger

Summary Aspergillus niger has been used as a host organism for the production of¹⁵N-labelled hen egg white lysozyme (HEWL). In order to achieve maximum incorporation of label, strains expressing the HEWL gene were grown in medium containing ammonium¹⁵N chloride as sole nitrogen source. Yields of HEWL protein were reduced relative to those obtained on more complex media. Gains in yield using complex media were offset by reduction in¹⁵N incorporation. No differences in either yield or kinetics of production were observed when ammonium¹⁵N chloride was replaced by unlabelled ammonium chloride as sole nitrogen source. Yields of¹⁵N-HEWL produced in this way are adequate for, and offer considerable advantages to, NMR studies of structure and folding of mutant and wild-type lysozymes.     

Using extensional flow to reveal diverse aggregation landscapes for three IgG1 molecules

Monoclonal antibodies (mAbs) currently dominate the biopharmaceutical sector due to their potency and efficacy against a range of disease targets. These proteinaceous therapeutics are, however, susceptible to unfolding, mis‐folding, and aggregation by environmental perturbations. Aggregation thus poses an enormous challenge to biopharmaceutical development, production, formulation, and storage. Hydrodynamic forces have also been linked to aggregation, but the ability of different flow fields (e.g., shear and extensional flow) to trigger aggregation has remained unclear. To address this question, we previously developed a device that allows the degree of extensional flow to be controlled. Using this device we demonstrated that mAbs are particularly sensitive to the force exerted as a result of this flow‐field. Here, to investigate the utility of this device to bio‐process/biopharmaceutical development, we quantify the effects of the flow field and protein concentration on the aggregation of three mAbs. We show that the response surface of mAbs is distinct from that of bovine serum albumin (BSA) and also that mAbs of similar sequence display diverse sensitivity to hydrodynamic flow. Finally, we show that flow‐induced aggregation of each mAb is ameliorated by different buffers, opening up the possibility of using the device as a formulation tool. Perturbation of the native state by extensional flow may thus allow identification of aggregation‐resistant mAb candidates, their bio‐process parameters and formulation to be optimized earlier in the drug‐discovery pipeline using sub‐milligram quantities of material.