Seasonal Changes in Colour: A Comparison of Structural,Melanin- and Carotenoid-Based Plumage Colours

Background

Plumage coloration is important for bird communication, most notably in sexual signalling. Colour is often considered a good quality indicator, and the expression of exaggerated colours may depend on individual condition during moult. After moult, plumage coloration has been deemed fixed due to the fact that feathers are dead structures. Still, many plumage colours change after moult, although whether this affects signalling has not been sufficiently assessed.

Methodology/Principal Findings

We studied changes in coloration after moult in four passerine birds (robin, Erithacus rubecula; blackbird, Turdus merula; blue tit, Cyanistes caeruleus; and great tit, Parus major) displaying various coloration types (melanin-, carotenoid-based and structural). Birds were caught regularly during three years to measure plumage reflectance. We used models of avian colour vision to derive two variables, one describing chromatic and the other achromatic variation over the year that can be compared in magnitude among different colour types. All studied plumage patches but one (yellow breast of the blue tit) showed significant chromatic changes over the year, although these were smaller than for a typical dynamic trait (bill colour). Overall, structural colours showed a reduction in relative reflectance at shorter wavelengths, carotenoid-based colours the opposite pattern, while no general pattern was found for melanin-based colours. Achromatic changes were also common, but there were no consistent patterns of change for the different types of colours.

Conclusions/Significance

Changes of plumage coloration independent of moult are probably widespread; they should be perceivable by birds and have the potential to affect colour signalling.     

Synaptic Metaplasticity Underlies Tetanic Potentiation in Lymnaea: A Novel Paradigm

We present a mathematical model that explains and interprets a novel form of short-term potentiation, which was found to be use-, but not time-dependent, in experiments done on Lymnaea neurons. The high degree of potentiation is explained using a model of synaptic metaplasticity, while the use-dependence (which is critically reliant on the presence of kinase in the experiment) is explained using a model of a stochastic and bistable biological switch.     

Perspectives: The Looking Time Experimental Paradigm in Studies of Animal Visual Perception and Cognition

Experiments are the foundation of empirical science, and experimental paradigms that are broadly applicable across settings and species are particularly useful for comparative research. Originally developed to address questions related to perception and cognition of pre‐verbal human infants, the looking time experimental paradigm has been increasingly used to study animal behavior and cognition, particularly in non‐human primates. Looking time experiments are based on the assumption that animals direct eye gaze toward objects or scenes based on their degree of interest, and use looking behavior to infer perceptual or cognitive characteristics of subjects. This paradigm can be used in a variety of contexts and is not based on species‐typical behaviors, allowing for intra‐ and interspecific comparisons. Here, we describe the history of use of looking time measures, provide an overview of the problems and controversies related to this method, and offer recommendations on how to implement looking time tasks, focusing on the preparation of stimuli, experimental procedures, and data analysis. Our overview focuses on non‐human primates, where most work has been carried out, but the issues discussed should be applicable to a wide range of species. We conclude that despite pertinent criticism, looking time tasks are practical when executed and interpreted properly. The further implementation of these methods in studies of animal behavior and cognition is likely to be fruitful.     

Evolution of Sex Determination and Sex Chromosomes: A Novel Alternative Paradigm

Sex chromosomes can differ between species as a result of evolutionary turnover, a process that can be driven by evolution of the sex determination pathway. Canonical models of sex chromosome turnover hypothesize that a new master sex determining gene causes an autosome to become a sex chromosome or an XY chromosome pair to switch to a ZW pair (or vice versa). Here, a novel paradigm for the evolution of sex determination and sex chromosomes is presented, in which there is an evolutionary transition in the master sex determiner, but the X chromosome remains unchanged. There are three documented examples of the novel paradigm, and it is hypothesized that a similar process could happen in a ZW sex chromosome system. Three other taxa are also identified where the novel paradigm may have occurred, and how it could be distinguished from canonical trajectories in these and additional taxa is also described.     

Influence of Rhythmic Grouping on Duration Perception: A Novel Auditory Illusion

This study investigated a potential auditory illusion in duration perception induced by rhythmic temporal contexts. Listeners with or without musical training performed a duration discrimination task for a silent period in a rhythmic auditory sequence. The critical temporal interval was presented either within a perceptual group or between two perceptual groups. We report the just-noticeable difference (difference limen, DL) for temporal intervals and the point of subjective equality (PSE) derived from individual psychometric functions based on performance of a two-alternative forced choice task. In musically untrained individuals, equal temporal intervals were perceived as significantly longer when presented between perceptual groups than within a perceptual group (109.25% versus 102.5% of the standard duration). Only the perceived duration of the between-group interval was significantly longer than its objective duration. Musically trained individuals did not show this effect. However, in both musically trained and untrained individuals, the relative difference limens for discriminating the comparison interval from the standard interval were larger in the between-groups condition than in the within-group condition (7.3% vs. 5.6% of the standard duration). Thus, rhythmic grouping affected sensitivity to duration changes in all listeners, with duration differences being harder to detect at boundaries of rhythm groups than within rhythm groups. Our results show for the first time that temporal Gestalt induces auditory duration illusions in typical listeners, but that musical experts are not susceptible to this effect of rhythmic grouping.     

Most and Least Preferred Colours Differ According to Object Context: New Insights from an Unrestricted Colour Range

Humans like some colours and dislike others, but which particular colours and why remains to be understood. Empirical studies on colour preferences generally targeted most preferred colours, but rarely least preferred (disliked) colours. In addition, findings are often based on general colour preferences leaving open the question whether results generalise to specific objects. Here, 88 participants selected the colours they preferred most and least for three context conditions (general, interior walls, t-shirt) using a high-precision colour picker. Participants also indicated whether they associated their colour choice to a valenced object or concept. The chosen colours varied widely between individuals and contexts and so did the reasons for their choices. Consistent patterns also emerged, as most preferred colours in general were more chromatic, while for walls they were lighter and for t-shirts they were darker and less chromatic compared to least preferred colours. This meant that general colour preferences could not explain object specific colour preferences. Measures of the selection process further revealed that, compared to most preferred colours, least preferred colours were chosen more quickly and were less often linked to valenced objects or concepts. The high intra- and inter-individual variability in this and previous reports furthers our understanding that colour preferences are determined by subjective experiences and that most and least preferred colours are not processed equally.     

A Novel Paradigm for Nonassociative Long-Term Memory in Drosophila: Predator-Induced Changes in Oviposition Behavior

Learning processes in Drosophila have been studied through the use of Pavlovian associative memory tests, and these paradigms have been extremely useful in identifying both genetic factors and neuroanatomical structures that are essential to memory formation. Whether these same genes and brain compartments also contribute to memory formed from nonassociative experiences is not well understood. Exposures to environmental stressors such as predators are known to induce innate behavioral responses and can lead to new memory formation that allows a predator response to persist for days after the predator threat has been removed. Here, we utilize a unique form of nonassociative behavior in Drosophila where female flies detect the presence of endoparasitoid predatory wasps and alter their oviposition behavior to lay eggs in food containing high levels of alcohol. The predator-induced change in fly oviposition preference is maintained for days after wasps are removed, and this persistence in behavior requires a minimum continuous exposure time of 14 hr. Maintenance of this behavior is dependent on multiple long-term memory genes, including orb2, dunce, rutabaga, amnesiac, and Fmr1. Maintenance of the behavior also requires intact synaptic transmission of the mushroom body. Surprisingly, synaptic output from the mushroom body (MB) or the functions of any of these learning and memory genes are not required for the change in behavior when female flies are in constant contact with wasps. This suggests that perception of this predator that leads to an acute change in oviposition behavior is not dependent on the MB or dependent on learning and memory gene functions. Because wasp-induced oviposition behavior can last for days and its maintenance requires a functional MB and the wild-type products of several known learning and memory genes, we suggest that this constitutes a paradigm for a bona fide form of nonassociative long-term memory that is not dependent on associated experiences.     

The Biodiversity Discourse: Categorisation of Indigenous People in a Mexican Bio-prospecting Case

Indigenous knowledge is often portrayed as static and traditional, while indigenous people are considered victims of exploitation. In the name of development and empowerment NGOs as well as scientists may run the risk of representing indigenous communities that fit their definition of the “correct” way to be indigenous. However, for indigenous people knowledge is not necessarily a static condition in a binary position to science or the ‘modern’ world. Rather, it is a dynamic condition that draws from experience and adapts to a changing environment. The perspective advanced in this paper is that all forms of knowledge, including indigenous knowledge(s), are situated and hybrid. Our argument draws from research carried out in Chiapas, Mexico, regarding the ICBG-Maya bio-prospecting project that was initiated in the 1990s and later terminated due to accusations of bio-piracy.     

Proteomics: A Paradigm Shift

ABSTRACT

Proteome—the protein complement of a genome—has become the protein renaissance and a key research tool in the post-genomic era. The basic technology involves the routine usage of gel electrophoresis and spectrometry procedures for deciphering the primary protein sequence/structure as well as knowing certain unique post-translational modifications that a particular protein has undergone to perform a specific function in the cell. However, the recent advancements in protein analysis have ushered this science to provide deeper, bigger and more valuable perspectives regarding performance of subtle protein-protein interactions. Applications of this branch of molecular biology are as vast as the subject is and include clinical diagnostics, pharmaceutical and biotechnological industries. The 21st century hails the use of products, procedures and advancements of this science as finer touches required for the grooming of fast-paced technology.     

A Novel Light Damage Paradigm for Use in Retinal Regeneration Studies in Adult Zebrafish

Light-induced retinal degeneration (LIRD) is commonly used in both rodents and zebrafish to damage rod and cone photoreceptors. In adult zebrafish, photoreceptor degeneration triggers Müller glial cells to re-enter the cell cycle and produce transient-amplifying progenitors. These progenitors continue to proliferate as they migrate to the damaged area, where they ultimately give rise to new photoreceptors. Currently, there are two widely-used LIRD paradigms, each of which results in varying degrees of photoreceptor loss and corresponding differences in the regeneration response. As more genetic and pharmacological tools are available to test the role of individual genes of interest during regeneration, there is a need to develop a robust LIRD paradigm. Here we describe a LIRD protocol that results in widespread and consistent loss of both rod and cone photoreceptors in which we have combined the use of two previously established LIRD techniques. Furthermore, this protocol can be extended for use in pigmented animals, which eliminates the need to maintain transgenic lines of interest on the albino background for LIRD studies.     

Neural Correlates of the Perception for Novel Objects

Perception of novel objects is of enormous importance in our lives. People have to perceive or understand novel objects when seeing an original painting, admiring an unconventional construction, and using an inventive device. However, very little is known about neural mechanisms underlying the perception for novel objects. Perception of novel objects relies on the integration of unusual features of novel objects in order to identify what such objects are. In the present study, functional Magnetic Resonance Imaging (MRI) was employed to investigate neural correlates of perception of novel objects. The neuroimaging data on participants engaged in novel object viewing versus ordinary object viewing revealed that perception of novel objects involves significant activation in the left precuneus (Brodmann area 7) and the right visual cortex. The results suggest that the left precuneus is associated with the integration of unusual features of novel objects, while the right visual cortex is sensitive to the detection of such features. Our findings highlight the left precuneus as a crucial component of the neural circuitry underlying perception of novel objects.     

Tetrapod Ichnofacies: A New Paradigm

We recognize three fundamental terms in ichnology: (1) ichnoassemblage, which is an assemblage of ichnofossils conceptually equivalent to an assemblage of body fossils; (2) ichnocoenosis, which is a trace fossil assemblage produced by a biological community that can be characterized by morphological criteria; and (3) ichnofacies, which refers to recurrent ichnocoenoses that represent a significant portion of Phanerozoic time. There are two different kinds of ichnofacies, ethoichnofacies (mostly invertebrate ichnofacies) and biotaxonichnofacies (mostly tetrapod ichnofacies). Nonmarine invertebrate ichnologists now recognize five archetypal ichnofacies (Mermia, Skolithos, Scoyenia, Coprinisphaera, Psilonichnus) to which we add the Octopodichnus ichnofacies. We propose a coherent and consistent classification and nomenclature for tetrapod ichnofacies. We name five archetypal vertebrate ichnofacies for nonmarine environments: Chelichnus, Grallator, Brontopodus, Batrachichnus and Characichnos ichnofacies.     

Novel and Transgenic Food Crops: Overview of Scientific Versus Public Perception

Recombinant DNA technology offers opportunities to develop new products in many different fields, including agriculture and the agro-food area. Transgenic plants with improved agronomic traits currently grow in field trials and a few varieties have already reached the European market. By and large, new technologies raise both concerns and expectations and modern biotechnology is no exception. Indeed, a voluntary moratorium on experiments involving recombinant DNA molecules was called for in 1974. At the present time, although a majority of academic and industrial scientists agree that transgenic food crops pose no risk for the environment or human health, some others believe that certain applications of modern plant biotechnology are hazardous. In particular, deliberate releases of genetically modified plants are regarded as risky. There is also a disparity between expert and lay perception of r-DNA technology applications to food crops, which makes public information a difficult task. This paper aims at exposing these conflicting points of view on the agricultural applications of modern biotechnology. We also propose some recommendations pertaining to public information in Europe. It appears that consensus conferences might be a good approach to stimulate public information and public debate in Europe, although this approach has to be adapted to the cultural context of each country.     

Noise-Induced Inner Hair Cell Ribbon Loss Disturbs Central Arc Mobilization: A Novel Molecular Paradigm for Understanding Tinnitus

Increasing evidence shows that hearing loss is a risk factor for tinnitus and hyperacusis. Although both often coincide, a causal relationship between tinnitus and hyperacusis has not been shown. Currently, tinnitus and hyperacusis are assumed to be caused by elevated responsiveness in subcortical circuits. We examined both the impact of different degrees of cochlear damage and the influence of stress priming on tinnitus induction. We used (1) a behavioral animal model for tinnitus designed to minimize stress, (2) ribbon synapses in inner hair cells (IHCs) as a measure for deafferentation, (3) the integrity of auditory brainstem responses (ABR) to detect differences in stimulus-evoked neuronal activity, (4) the expression of the activity-regulated cytoskeletal protein, Arc, to identify long-lasting changes in network activity within the basolateral amygdala (BLA), hippocampal CA1, and auditory cortex (AC), and (5) stress priming to investigate the influence of corticosteroid on trauma-induced brain responses. We observed that IHC ribbon loss (deafferentation) leads to tinnitus when ABR functions remain reduced and Arc is not mobilized in the hippocampal CA1 and AC. If, however, ABR waves are functionally restored and Arc is mobilized, tinnitus does not occur. Both central response patterns were found to be independent of a profound threshold loss and could be shifted by the corticosterone level at the time of trauma. We, therefore, discuss the findings in the context of a history of stress that can trigger either an adaptive or nonadaptive brain response following injury.