Finding an assay that reveals effects of sleep deprivation on decision making in Drosophila

This study makes use of cutting-edge technology to tackle the intricate links between decision making and sleep in the Drosophila Melanogaster fly using various innovative behavioural paradigms. The assays developed are iteratively improved to be suitable for high-throughput experiments and automatic video tracking of desired features. The final paradigm presents the fly with the simple decision of passing through two holes of different sizes: a large hole through which it can pass easily and a smaller one through which it can pass with some difficulty. Independently of the external conditions such as light, shape of the assay and time of the day or of the internal states such as genetic background and sleep state, all the flies choose to make multiple passages through both holes and unanimously show a preference for the bigger hole. Our paradigm is unique in that it allow us to assess flies decisions independently of the locomotion state by evaluating the proportion of passages through the two holes. Remarkably, this parameter is conserved in the same genetic background. Moreover, our results confirm and strengthen previous studies showing that locomotion is increased by space restriction in males. When faced with our non-conventional paradigms, after prolonged sleep deprivation, flies suppress their sleep rebound. In addition, they show no behavioural differences to control flies. It appears that the sleep pressure built up through homeostatic regulation is not important enough to counteract the in- creased arousal state resulted from space restriction in order to trigger sleep. However, when experiments are performed in the afternoon during flies ”siesta”, they fall asleep, indicating that the sleep pressure arising from circadian regulation is more significant than the sleep pressure coming from homeostatic regulation.Open Acces

Diversity and Evolution of Butterfly Wing Patterns: An Integrative Approach

nymphalid; ecology; evolution; genetics; mimicr

Novel morphological and physiological scaling relationships in the southern red wood ant

Red wood ants (Formica rufa) are visual navigators whose colonies contain workers that differ substantially in size. By investigating the allometry of the ants’ compound eyes, and the regions within them, I showed that facets in particular regions scaled differently: both grade and slope shifts occurred. Facets in some eye regions were absolutely larger than others, while other facet regions scaled at different rates with body size. I next compared eye scaling between nests from the same population. Nevertheless, the method by which ants increased their eye size differed between nests. I found that ants from some nests primarily increased eye size through facet number and others through facet diameter. This showed that scaling rules at the cellular levels can differ even within a single population. Comparisons among Formica species revealed that differential eye scaling was not restricted to just F. rufa. Differential scaling was found in F. sanguinea but not F. lugubris or F. fusca. Surprisingly, scaling between facet diameter and number was conserved across all four species, demonstrating that whole-organ scaling among species can be conservative whilst differing vastly between organ-regions. Moving beyond morphology, I next investigated whether physiological scaling was equally as variable among nests. Metabolic rate scaling was negatively allometric and the same among four nests. Respiratory water loss was found to be determined solely by metabolic rate. Metabolic rate co-varies with different ventilation types, however, switches in ventilation type are driven by movement. This demonstrates that increases in metabolic rate are not sufficient to explain changes in ventilation type but are sufficient to explain respiratory water loss

The role of visual adaptation in cichlid fish speciation

D. Shane Wright (1) , Ole Seehausen (2), Ton G.G. Groothuis (1), Martine E. Maan (1) (1) University of Groningen; GELIFES; EGDB(2) Department of Fish Ecology & Evolution, EAWAG Centre for Ecology, Evolution and Biogeochemistry, Kastanienbaum AND Institute of Ecology and Evolution, Aquatic Ecology, University of Bern.In less than 15,000 years, Lake Victoria cichlid fishes have radiated into as many as 500 different species. Ecological and sexual sel ection are thought to contribute to this ongoing speciation process, but genetic differentiation remains low. However, recent work in visual pigment genes, opsins, has shown more diversity. Unlike neighboring Lakes Malawi and Tanganyika, Lake Victoria is highly turbid, resulting in a long wavelength shift in the light spectrum with increasing depth, providing an environmental gradient for exploring divergent coevolution in sensory systems and colour signals via sensory drive. Pundamilia pundamila and Pundamilia nyererei are two sympatric species found at rocky islands across southern portions of Lake Victoria, differing in male colouration and the depth they reside. Previous work has shown species differentiation in colour discrimination, corresponding to divergent female preferences for conspecific male colouration. A mechanistic link between colour vision and preference would provide a rapid route to reproductive isolation between divergently adapting populations. This link is tested by experimental manip ulation of colour vision - raising both species and their hybrids under light conditions mimicking shallow and deep habitats. We quantify the expression of retinal opsins and test behaviours important for speciation: mate choice, habitat preference, and fo raging performance

Models of self-organization in biological development

Bibliography: p. 297-320.In this thesis we thus wish to consider the concept of self-organization as an overall paradigm within which various theoretical approaches to the study of development may be described and evaluated. In the process, an attempt is made to give a fair and reasonably comprehensive overview of leading modelling approaches in developmental biology, with particular reference to self-organization. The work proceeds from a physical or mathematical perspective, but not unduly so - the major mathematical derivations and results are relegated to appendices - and attempts to fill a perceived gap in the extant review literature, in its breadth and attempted impartiality of scope. A characteristic of the present account is its markedly interdisciplinary approach: it seeks to place self-organization models that have been proposed for biological pattern formation and morphogenesis both within the necessary experimentally-derived biological framework, and in the wider physical context of self-organization and the mathematical techniques that may be employed in its study. Hence the thesis begins with appropriate introductory chapters to provide the necessary background, before proceeding to a discussion of the models themselves. It should be noted that the work is structured so as to be read sequentially, from beginning to end; and that the chapters in the main text were designed to be understood essentially independently of the appendices, although frequent references to the latter are given. In view of the vastness of the available information and literature on developmental biology, a working knowledge of embryological principles must be assumed. Consequently, rather than attempting a comprehensive introduction to experimental embryology, chapter 2 presents just a few biological preliminaries, to 'set the scene', outlining some of the major issues that we are dealing with, and sketching an indication of the current status of knowledge and research on development. The chapter is aimed at furnishing the necessary biological, experimental background, in the light of which the rest of the thesis should be read, and which should indeed underpin and motivate any theoretical discussions. We encounter the different hierarchical levels of description in this chapter, as well as some of the model systems whose experimental study has proved most fruitful, some of the concepts of experimental embryology, and a brief reference to some questions that will not be addressed in this work. With chapter 3, we temporarily move away from developmental biology, and consider the wider physical and mathematical concepts related to the study of self-organization. Here we encounter physical and chemical examples of spontaneous structure formation, thermodynamic considerations, and different approaches to the description of complexity. Mathematical approaches to the dynamical study of self-organization are also introduced, with specific reference to reaction-diffusion equations, and we consider some possible chemical and biochemical realizations of self-organizing kinetics. The chapter may be read in conjunction with appendix A, which gives a somewhat more in-depth study of reaction-diffusion equations, their analysis and properties, as an example of the approach to the analysis of self-organizing dynamical systems and mathematically-formulated models. Appendix B contains a more detailed discussion of the Belousov-Zhabotinskii reaction, which provides a vivid chemical paradigm for the concepts of symmetry-breaking and self-organization. Chapter 3 concludes with a brief discussion of a model biological system, the cellular slime mould, which displays rudimentary development and has thus proved amenable to detailed study and modelling. The following two chapters form the core of the thesis, as they contain discussions of the detailed application of theoretical concepts and models, largely based on self-organization, to various developmental situations. We encounter a diversity of models which has arisen largely in the last quarter century, each of which attempts to account for some aspect of biological pattern formation and morphogenesis; an aim of the discussion is to assess the extent of the underlying unity of these models in terms of the self-organization paradigm. In chapter 4 chemical pre-patterns and positional information are considered, without the overt involvement of cells in the patterning. In chapter 5, on the other hand, cellular interactions and activities are explicitly taken into account; this chapter should be read together with appendix C, which contains a brief introduction to the mathematical formulation and analysis of some of the models discussed. The penultimate chapter, 6, considers two other approaches to the study of development; one of these has faded away, while the other is still apparently in the ascendant. The assumptions underlying catastrophe theory, the value of its applications to developmental biology and the reasons for its decline in popularity, are considered. Lastly, discrete approaches, including the recently fashionable cellular automata, are dealt with, and the possible roles of rule-based interactions, such as of the so-called L-systems, and of fractals and chaos are evaluated. Chapter 7 then concludes the thesis with a brief assessment of the value of the self-organization concept to the study of biological development