The Value of Artificial Stimuli in Behavioral Research: Making the Case for Egg Rejection Studies in Avian Brood Parasitism

Experimentation is at the heart of classical and modern behavioral ecology research. The manipulation of natural cues allows us to establish causation between aspects of the environment, both internal and external to organisms, and their effects on animals' behaviors. In recognition systems research, including the quest to understand the coevolution of sensory cues and decision rules underlying the rejection of foreign eggs by hosts of avian brood parasites, artificial stimuli have been used extensively, but not without controversy. In response to repeated criticism about the value of artificial stimuli, we describe four potential benefits of using them in egg recognition research, two each at the proximate and ultimate levels of analysis: (1) the standardization of stimuli for developmental studies and (2) the disassociation of correlated traits of egg phenotypes used for sensory discrimination, as well as (3) the estimation of the strength of selection on parasitic egg mimicry and (4) the establishment of the evolved limits of sensory and cognitive plasticity. We also highlight constraints of the artificial stimulus approach and provide a specific test of whether responses to artificial cues can accurately predict responses to natural cues. Artificial stimuli have a general value in ethological research beyond research in brood parasitism and may be especially critical in field studies involving the manipulation of a single parameter, where other, confounding variables are difficult or impossible to control experimentally or statistically.     

A novel application of entropy analysis for assessing changes in movement variability during cumulative tackles in young elite rugby league players

The aim of this study was to identify between-position (forwards vs. backs) differences in movement variability in cumulative tackle events training during both attacking and defensive roles. Eleven elite adolescent male rugby league players volunteered to participate in this study (mean ± SD, age; 18.5 ± 0.5 years, height; 179.5 ± 5.0 cm, body mass; 88.3 ± 13.0 kg). Participants performed a drill encompassing four blocks of six tackling (i.e. tackling an opponent) and six tackled (i.e. being tackled by an opponent while carrying a ball) events (i.e. 48 total tackles) while wearing a micro-technological inertial measurement unit (WIMU, Realtrack Systems, Spain). The acceleration data were used to calculate sample entropy (SampEn) to analyse the movement variability during tackles performance. In tackling actions SampEn showed significant between-position differences in block 1 (p = 0.0001) and block 2 (p = 0.0003). Significant between-block differences were observed in backs (block 1 vs 3, p = 0,0021; and block 1 vs 4, p = 0,0001) but not in forwards. When being tackled, SampEn showed significant between-position differences in block 1 (p = 0.0007) and block 3 (p = 0.0118). Significant between-block differences were only observed for backs in block 1 vs 4 (p = 0,0025). Movement variability shows a progressive reduction with cumulative tackle events, especially in backs and when in the defensive role (tackling). Forwards present lower movement variability values in all blocks, particularly in the first block, both in the attacking and defensive role. Entropy measures can be used by practitioners as an alternative tool to analyse the temporal structure of variability of tackle actions and quantify the load of these actions according to playing position.     

Protein oxidative damage and redox imbalance induced by ionising radiation in CHO cells

Reactive oxygen species (ROS) are important mediators of the cytotoxicity induced by the direct reaction of ionising radiation (IR) with all critical cellular components, such as proteins, lipids, and nucleic acids. The derived oxidative damage may propagate in exposed tissues in a dose- and spatiotemporal dependent manner to other cell compartments, affecting intracellular signalling, and cell fate. To understand how cell damage is induced, we studied the oxidative events occurring immediately after cell irradiation by analysing the fate of IR-derived ROS, the intracellular oxidative damage, and the modification of redox environment accumulating in Chinese hamster ovary (CHO) within 1?h after cell irradiation (dose range 0–10?Gy). By using the immuno-spin trapping technique (IST), spectrophotometric methods, and electron paramagnetic resonance (EPR) spectroscopy, we showed that IR-derived ROS (i) induced an IST-detectable, antioxidant-inhibitable one-electron oxidation of specific intracellular proteins; (ii) altered the glutathione (GSH) content (which was found to increase below 2?Gy, and decrease at higher doses, leading to a redox imbalance); (iii) decreased glutathione peroxidase and glutaredoxin activity; (iv) modified neither glutathione reductase nor thioredoxin reductase activity; (v) were detected by spin trapping technique, but adduct intensity decreased due to cell competition for ROS; and (vi) induced no EPR-detectable radicals assignable to oxidised cellular components. In conclusion, our results showed that IR generated an early high oxidising potential (protein radical intermediates, redox imbalance, modified redox enzyme activity) in irradiated cells potentially able to propagate the damage and induce oxidative modification of secondary targets.     

The Role of Voluntary Industry Standards in Environmental Supply-Chain Management

Our article uses a new institutional economics (NIE) framework to explore the role of voluntary industry standards in the development and implementation of environmental supplier-management programs in the computer industry. We examine two different voluntary standards, one for the management of design for environment (DfE) in the semiconductor fabrication equipment sector and the other for assessing the implementation and use of environmental management systems throughout the computer industry supply chain. We compare and contrast the two standards to explain why the former was widely adopted and has helped integrate DfE into buyer-supplier relations among adopters, whereas the latter failed to gain acceptance. In line with NIE logic, both standards aimed to lower transaction and customization costs by setting "rules of the game" for interfirm transactions that would help simplify and routinize novel environmental supply-chain programs and activities. Their differential success can be elucidated in terms of how well each met the NIE criteria for remediableness and legitimacy. We conclude that voluntary standards have the potential to play an important role in promoting DfE in industrial supply chains. We further conclude that NIE provides a conceptual framework of great value to industrial ecologists who analyze how industry standards and other institutions help firms move toward more sustainable supply-chain management practices.     

Conflicting selection pressures on reproductive functions and speciation in plants

Recent developments in the field of genetic divergence and speciation focus more on diversifying processes than on geographic mode of speciation (i.e. allopatric versus sympatric). Some of these new theories concern speciation driven by conflicts between the sexes. Even though it is well known that the two reproductive functions in plants can have different selective optima, sexual selection in plants is by many assumed to be weak or non-existent. Here we outline potential sexual conflicts in plants and discuss how selection pressures generated by such conflicts may influence genetic divergence. There is opportunity for conflicting selection pressures between individuals, such as manipulative pollen traits that enhance male reproductive success at the expense of the female reproductive function. Within individual plants, fitness of the male function (pollen export) and fitness of the female function (pollen import) may be optimised by different traits, leading to conflicting selection pressures in relation to pollen transfer. This may affect selection for floral specialisation versus floral generalisation in animal-pollinated species. We believe that selection pressures generated by sexual conflict need to be appreciated in order to fully understand microevolutionary processes which may lead to genetic divergence and speciation in plants.     

The manifold characters of orbicules: structural diversity,systematic significance,and vectors for allergens

In the anthers of flowering plants, gymnosperms, and seed ferns, tiny (±1?μm) granules might occur on the radial and innermost tangential wall of secretory tapetum cells. These sporopollenin granules develop simultaneously with the pollen exine and are called orbicules or Ubisch bodies. The present paper focuses on two quite different topics associated with orbicules.

The morphological and ultrastructural diversity of orbicules in the order Gentianales is summarized, and it is demonstrated that orbicules are a plesiomorphic feature in the order. Furthermore, orbicule characters seemed to be correlated with evolutionary trends in pollen dispersal unit and tapetum type features.

In the second part, we report on our investigation of Corylus avellana L. (Hazel) pollen, using immunogold electron microscopy to gain an insight into the possible role that orbicules may play as a vector of pollen allergens. During the pollen season orbicules are dispersed into the atmosphere along with Hazel pollen grains. The localisation of homologues of the new birch pollen allergen Bet v 7 was studied at the subcellular level in Hazel anthers. The results of this study indicate that orbicules and pollen of Hazel might act as very effective vectors for homologues of Bet v 7 and that debris of Hazel anthers represent vectors of allergens after the pollen season.     

Divergence in male mating tactics between two populations of the soapberry bug: I. Guarding versus nonguarding

I compared male allocation to prolonged mate guarding versusnot guarding between two populations of the soapberry bug (Jaderahaematoloma) that differ in adult sex ratio: Oklahoma, USA (mean± SD adult sex ratio, 2.70 ± 0.95 males per female),and Florida, USA (1.09 ± 0.26 males per female). To predictthe reproductive performance of each mating tactic in each population,I collected data on search time per mating, time required forguarding to be effective, sperm competition, female rematingpropensity, and female resistance to guarding. Search time alonediffered significantly between the populations, being much greaterin Oklahoma (estimated as 26.2 h per mate) than in Florida (estimatedas 9.6 h per mate). For males in each region, these data wereused to model the costs and benefits of guarding for differentnumbers of oviposition bouts versus not guarding. The reproductiverate of nonguarders in Oklahoma is exceeded by that of guarderswho remain with a female for more than one oviposition bout,but in Florida, the reproductive rate of nonguarders is onlyexceeded by that of guarders who remain with a female for atleast three ovipositions. Consistent with the model, Oklahomamales in field arenas guarded more frequently than did Floridamales. However, nonguarding was common in both populations,and guarding durations were highly variable.     

Formation of heterocyclic aromatic amines in model systems

Heterocyclic aromatic amines (HAs) are mutagenic and carcinogenic substances that are formed in significant amounts during heating of meat or fish at temperatures of at least 150 degrees C. To investigate the chemistry lying behind the formation of these harmful substances model systems were established. The first aim was to identify the naturally occurring precursors, namely creatinine, amino acids and carbohydrates. Later these model systems were used to develop strategies for a reduction of the content of the heterocyclic aromatic amines and for the evaluation of the reaction mechanisms that lead to the formation of these substances. All these aspects are discussed in this review.