Calcium and salinity as selective factors in plate morph evolution of the three-spined stickleback (Gasterosteus aculeatus).

Identifying the causal factors underlying natural selection remains a key challenge in evolutionary biology. Although the genetic basis for the plate morph evolution of three-spined stickleback (Gasterosteus aculeatus) is well described, the environmental variables that form the basis for different morphs are not understood. We measured the effects of dissolved calcium and salinity on the growth of sticklebacks with different plate morphs from Scotland and Poland. There was a significant interaction of calcium with plate morph for fish from both regions, with complete morph sticklebacks growing more slowly at low calcium concentrations and low morph sticklebacks showing divergent responses to calcium concentration. A Scottish anadromous population showed evidence of local adaptation to high salinity, which was independent of plate morph. Polish and Scottish populations diverged in their response to salinity, suggesting a difference in osmotic regulation. The results implicate a role for calcium in selecting for plate morph evolution in sticklebacks, possibly as a limiting element in skeletal growth.

Effect of spawning number and ration on reproductive performance of the batch-spawning three-spined stickleback Gasterosteus aculeatus.

An experiment quantified the effect of food ration and spawning number on the breeding season reproductive performance of batch-spawning, female three-spined sticklebacks Gasterosteus aculeatus. Individually housed females were maintained on fixed rations of 2, 4, 8 or 16% of their initial postspawning mass of live enchytraeid worms from immediately after their first spawning until they ceased spawning. Number of spawnings correlated positively with ration. Total breeding season reproductive investment (total wet mass of eggs produced as a percentage of initial postspawning female mass) ranged from 38% at the 2% ration to 147% at the 16% ration. At the lower rations, postspawning mass, batch fecundity and wet and dry masses of the batch declined over successive spawnings, with the rate of decline inversely related to ration. At the highest ration, there was no decline in batch fecundity and postspawning mass increased over successive spawnings. Mean reproductive investment per inter-spawning interval was higher at the highest ration, but at all rations declined over successive spawnings. Mean reproductive effort per inter-spawning interval (wet mass of eggs spawned as a percentage of the wet mass of food consumed over the inter-spawning interval) was inversely related to ration. At the higher rations, reproductive effort showed no trend over successive spawnings. Neither spawning number nor ration had a systematic effect on egg diameter, wet mass per egg, dry mass per egg or total lipid content of the eggs. If the rate of food intake was insufficient, although batch fecundity declined, the main adjustment was a reduction in the number of spawnings in the breeding season.

The Darwinian stickleback Gasterosteus aculeatus: a history of evolutionary studies.

The history of studies on the taxonomy and evolutionary biology of the three-spined stickleback Gasterosteus aculeatus from the 18th century to the present is reviewed. After the publication of Darwin's Origin of the Species, four important dates, 1925, 1947, 1967 and 2001, are identified as marking major gains in the understanding of the evolution of the diversity in morphological, life-history, physiological and behavioural traits that characterizes G. aculeatus. The period 1925-1970 led to the identification of the main themes of research: status and adaptive significance of lateral-plate morphs; inter and intrapopulation trait variation in freshwater resident G. aculeatus and the adaptive significance of the variation. Between 1970 and 2001, these themes were investigated using variation observed particularly along the Pacific coast of the U.S.A. and Canada, notably in the Cook Inlet region of Alaska and the Haida Gwaii Archipelago. Studies on adaptive radiation and reproductive isolation in lacustrine, ecomorph pairs (limnetics and benthics) discovered in the Strait of Georgia region have been particularly productive. From 2001, the application of genomic studies to these problems began to open up the study of the relationships between genotype, phenotype and selective advantage to causal analysis.

Detailed optical study of the transparent wing membranes of the dragonfly Aeshna cyanea.

The optical properties of transparent single membranes on the wings of the dragonfly Aeshna cyanea have been investigated. These membranes comprise one central thick cuticular layer covered dorsally and ventrally with typical odonatan wax pruinosity. Optical characterisation of individual membranes reveals they can support optical guided modes comprising differential polarisation reflection. We suggest this may offer an intraspecific signalling channel. The guided modes' characteristics depend on membrane thickness and the nature of the wax pruinosity. We accurately modelled multiple optical data sets simultaneously, thereby inaugurally quantifying the roughness of the pruinosity and the complex refractive indices of the wax and the odonatan cuticle.

Remarkable iridescence in the hindwings of the damselfly Neurobasis chinensis chinensis (Linnaeus) (Zygoptera: Calopterygidae).

The bright green dorsal iridescence of the hindwings of Neurobasis chinensis chinensis males, very rare in Odonata, is known to play a significant role in their courtship behaviour. The mechanism responsible for such high contrast and spectrally pure colour has been investigated and found to be optical interference, producing structural colour from distinct laminations in the wing membrane cuticle. The ventral sides of these iridescent wings are dark brown in colour. In a single continuous membrane of wing cuticle, this is an effect that requires a specialized structure. It is accomplished through the presence of high optical absorption (kappa = 0.13) within two thick layers near the ventral surface of the wing, which leads to superior dorsal colour characteristics. By simultaneously fitting five sets of optical reflectivity and transmissivity spectra to theory, we were able to extract very accurate values of the complex refractive index for all three layer types present in the wing. The real parts of these are n = 1.47, 1.68 and 1.74. Although there is often similarly significant dorsal and ventral colour contrast in other structurally coloured natural systems, very few system designs comprise only a single continuous membrane.

Approaches to the structural modelling of insect wings.

Insect wings lack internal muscles, and the orderly, necessary deformations which they undergo in flight and folding are in part remotely controlled, in part encoded in their structure. This factor is crucial in understanding their complex, extremely varied morphology. Models have proved particularly useful in clarifying the facilitation and control of wing deformation. Their development has followed a logical sequence from conceptual models through physical and simple analytical to numerical models. All have value provided their limitations are realized and constant comparisons made with the properties and mechanical behaviour of real wings. Numerical modelling by the finite element method is by far the most time-consuming approach, but has real potential in analysing the adaptive significance of structural details and interpreting evolutionary trends. Published examples are used to review the strengths and weaknesses of each category of model, and a summary is given of new work using finite element modelling to investigate the vibration properties and response to impact of hawkmoth wings.

Limited-view iridescence in the butterfly Ancyluris meliboeus.

Few mechanisms exist in nature that effect colour reflectivity, simultaneously high in spectral purity and in intensity, over a strictly limited portion of solid angle above a surface. Fewer still bring about such colour reflectivity with an angle dependence that is distinct from the colour transition associated with conventional multilayer interference. We have discovered that the ventral wings of the butterfly Ancyluris meliboeus exhibit these optical effects, and that they result from remarkable nano-scale architecture on the wing scales of the butterfly. This nano-structure is in the form of high-tilt multilayering that, as a result of abrupt termination of the multilayers, brings about diffraction concurrently with interference. The product is bright structural colour in a limited angular region over the ventral wing surface that enables remarkably strong flicker and colour contrast through minimal wing movement. The visibility effects associated with its colour, in terms of bright and dark zones of the observation hemisphere over the wing surface, are described. We suggest the purpose of the high-contrast ventral wing visibility associated with A. meliboeus is at-rest signalling; this is distinct from the dorsal wing visibility of other species such as those of the genus Morpho, the function of which is largely for in-flight signalling.

The hind wing of the desert locust (Schistocerca gregaria Forskål). I. Functional morphology and mode of operation.

Detailed morphological investigation, mechanical testing and high-speed cinematography and stroboscopic examination of desert locusts, Schistocerca gregaria, in flight show that their hind wings are adapted to deform cyclically and automatically through the wing stroke and that the deformations are subtly dependent on the wings' structure: their shape, venation and vein design and the local properties of the membrane. The insects predominantly fly fast forwards, generating most force on the downstroke, and the hind wings generate extra lift by peeling apart at the beginning of the downstroke and by developing a cambered section during the stroke's translation phase through the 'umbrella effect' - an automatic consequence of the active extension of the wings' expanded posterior fan. Bending experiments indicate that most of the hind wing is more rigid to forces from below than from above and demonstrate that the membrane acts as a stressed skin to stiffen the structure.

The hind wing of the desert locust (Schistocerca gregaria Forskål). II. Mechanical properties and functioning of the membrane.

As part of an investigation of the functional mechanics of the hind wing of the desert locust Schistocerca gregaria, the Young's modulus of the membrane was measured using a newly developed universal materials test machine capable of testing very small specimens of cuticle, down to 1 mm gauge length. Strain was measured optically. Specimens were cut from various locations around the wing and tested under controlled temperature and humidity. The modulus of the membrane was typically between 1 and 5 GPa, but both this and the membrane thickness varied around the wing, with the remigium and the anal fan showing markedly different properties. The membrane was tested for chitin using two methods: a gas pyrolysis/mass spectrometry assay, and a gold-labelled immunoassay specific to chitin. None was detected, and the membrane may consist of epicuticle alone. The wings were examined for evidence of crystalline material using standard polarising microscopy and an advanced technique that distinguishes between three components of the polarised image. Birefringence was detected in the membrane of the anterior part of the wing, but vanished when the membrane was separated from the surrounding veins, suggesting that it was due to pre-stress rather than to ultrastructure. The implications are discussed.

The hind wing of the desert locust (Schistocerca gregaria Forskål). III. A finite element analysis of a deployable structure.

Finite element analysis is used to model the automatic cambering of the locust hind wing during promotion: the umbrella effect. It was found that the model required a high degree of sophistication before replicating the deformations found in vivo. The model has been validated using experimental data and the deformations recorded both in vivo and ex vivo. It predicts that even slight modifications to the geometrical description used can lead to significant changes in the deformations observed in the anal fan. The model agrees with experimental data and produces deformations very close to those seen in free-flying locusts. The validated model may be used to investigate the varying geometries found in orthopteran anal fans and the stresses found throughout the wing when loaded.

Flight adaptations in Palaeozoic Palaeoptera (Insecta).

The use of available morphological characters in the interpretation of the flight of insects known only as fossils is reviewed, and the principles are then applied to elucidating the flight performance and techniques of Palaeozoic palaeopterous insects. Wing-loadings and pterothorax mass/total mass ratios are estimated and aspect ratios and shape-descriptors are derived for a selection of species, and the functional significance of wing characters discussed. Carboniferous and Permian ephemeropteroids ('mayflies') show major differences from modern forms in morphology and presumed flight ability, whereas Palaeozoic odonatoids ('dragonflies') show early adaptation to aerial predation on a wide size-range of prey, closely paralleling modern dragonflies and damselflies in shape and wing design but lacking some performance-related structural refinements. The extensive adaptive radiation in form and flight technique in the haustellate orders Palaeodictyoptera, Megasecoptera, Diaphanopterodea and Permothemistida is examined and discussed in the context of Palaeozoic ecology.

Elastic joints in dermapteran hind wings: materials and wing folding.

Representatives of Dermaptera probably have the most unusual hind wing venation and folding pattern among insects. Both correlate with unusual wing folding mechanics, in which folding is achieved from within the wing and unfolding is done by the cerci. In this account, the hind wings of the earwig Forficula auricularia were studied by means of bright field and fluorescence microscopy. Resilin, a rubber-like protein, was revealed in several, clearly defined patches. It occurs dorsally in the radiating veins, but ventrally in the intercalary vein. This distribution determines the folding direction, and resilin is the major driving mechanism for wing folding. Resilin stores elastic energy in broadened vein patches and along the folds. At the other locations, the mid-wing mechanism and central area, the primary function of resilin is suggested to be prevention of material failure. The arrangement of resilin patches is such that the wing cannot be unfolded from the thorax proper but must be unfolded by the cerci. In Dermaptera, the antagonistic movements of folding and unfolding are achieved in two different ways, resilin and cerci. To our knowledge this is unique.

Invertebrate paraxial locomotory appendages: design, deformation and control.

Some principles governing the design of invertebrate paired propulsive appendages are discussed, with particular reference to the extent to which information encoded in their skeletal structure determines their instantaneous shape in locomotion. The hydrostatic paired fins of some cephalopods and marine gastropods, polychaete parapodia and onychophoran lobopodia rely entirely on musculature for shape control. The deformations of walking limbs, though still under muscular control, are strongly influenced by the nature and sequence of movement of the joints. Limbs adapted for walking in air are effectively point-loaded, and their rigid components need to resist axial forces as well as bending and torsional moments. Aquatic walking limbs have little axial loading, while swimming appendages and wings experience only bending and torsional moments, and can exploit these to assist in the deformations that are necessary to gain force asymmetry between half-strokes. Swimming appendages normally employ both muscles and drag, but the wings of insects lack internal muscles, and their changes in shape are largely complex aeroelastic responses to the constantly changing aerodynamic and inertial loads, moderated by muscles inserted at the base. For illustration, wings modelled as thin shells with flexible hinge-lines are used to investigate how transverse distal flexion, essential for controlling the angle of attack in the upstroke, is remotely controlled by the indirect flight muscles.

An immunological assessment of group-housed rabbits.

Laboratory rabbits kept in barren 'traditional' cages tend to develop stereotypic behaviours and bone deformities. We have used an alternative regime, housing adult does as groups of four or five in floor pens (2.5-3 m2) supplied with hiding places and bedding. High- and low-ranking members of each group were identified, and their immunological status compared in terms of blood leucocyte function (chemiluminescence and mitogen tests), complement activity, and antibody production to soluble and cellular antigens. We found no evidence of immunosuppression, either in groups of a 'docile' breed (New Zealand White) or Dutch crosses. These results, together with the animals' general health and ease of handling, lead us to conclude that group-housed does are suitable for raising antisera and other purposes, provided that they are adequately monitored.

Effect of water pH and salinity on the survival of eggs and larvae of the euryhaline teleost, Gasterosteus aculeatus L.

The effect of water acidification and salinity on the survival of the eggs and larvae of the euryhaline teleost, Gasterosteus aculeatus, was studied using tap water that was low in calcium and high in total aluminium as the basic medium. The survival of eggs from fertilisation to hatching increased with an increase in pH from 4.5 to 6.5. Survival was higher at a given pH at higher salinities (equivalent to 5% and 10% seawater) than in tap water. The salinity experienced by the female prior to spawning also had an effect on egg survival. Survival for 7 days after hatching was high except at the lowest pH levels. The salinity experienced by the female had no significant effect on larval survival.

Dramatic religious conversion and schizophrenic decompensation.

The similarities between dramatic religious and psychotic experiences have long been observed and, just as long, have proved a source of confusion and misunderstanding. Recent surveys on decompensation to schizophrenic psychosis offer not only striking comparisons to the phenomenon of sudden and dramatic religious conversion but clues to the limits of continuity between these two mental processes. Using Docherty and his associates model of the stages of onset of schizophrenic psychosis and their own review of the literature of religious conversion, the authors suggest three principal similarities and the point of departure between the two phenomena.

Motivation dependence of brain self-stimulation in the pigeon.

Several brain sites in the pigeon were identified as maintaining electrical brain self-stimulation. Depending on the site, stimulus currents yielding maximal responding varied from 20 to 160 µA. A high proportion of the sites only yielded self-stimulation behaviour if the subjects were deprived of food; when the birds were at full weight there was only one site at which the stimulation continued to be rewarding. Some, but weak, evidence of stimulus satiation was found. Overt behaviour elicited by non-contingent stimulation did not correlate with the reinforcing or neutral nature of the sites tested. While some positive sites were associated with structures known to be involved in the control of feeding, others were not. The hypothesis that stimulation at the hunger-dependent sites might have elicited temporary satiation signals is considered.