Functional morphology of the visual system and mating strategies in bumblebees (Hymenoptera,Apidae, Bombus)

Bumblebee mating behaviour intrigued Darwin over 150 years ago and has elicited much interest since. Despite our increasing knowledge about male mating strategies, we still know little about the signals and cues involved, the sender‐receiver relationship and the functional adaptations of the involved sensory systems. Although several authors have noticed a close relationship between the mating system and male‐specific elaboration of the visual system, studies on the functional adaptations have yet to be conducted. We investigated the functional morphology of the compound eyes in 11 species of Bombus from various subgenera in detail. Of these, four species (Bombus confusus, Bombus melaleucus, Bombus mendax, Bombus niveatus) have enlarged male eyes, characterized by a higher number of ommatidia compared with worker eyes and a frontal zone with enlarged facets, which is likely to be associated with improved spatial resolution and contrast sensitivity. In these species, perching mating strategies are found. In contrast, males of species that patrol scent routes (Bombus hortorum, Bombus lapidarius, Bombus pascuorum, Bombus pratorum, Bombus soroeensis, Bombus terrestris, Bombus wurflenii) show no distinct eye adaptations, and their eye morphology closely resembles that of the workers. A phylogenetic analysis of male eye structure indicates that enlarged males eyes may have been the ancestral state in Bombus. © 2014 The Linnean Society of London     

Neurotransplantation of the Biological Clock in Mammals,Importance and Perspectives

The tool of neurotransplantation has been successfully introduced in the chronobiology of mammals. Grafting of the foetal suprachiasmatic nucleus (SCN) in the IIIrd ventricle of the brain of SCN-lesioned arhythmic rodents restored free-running circadian activity patterns. This ultimately proves the SCN to be the central circadian pacemaker system. However, recovery is not seen in all animals with a surviving SCN implant and the rhythm is usually not as robust as seen for the intact system. Moreover, the grafted foetal SCN has a partially deviant development, whereas the structure-function relationship after restoration of circadian rhythm was reported to differ in the various studies. This has led to two possible mechanisms of graft action: the one a circadian humoral signal diffusing into the SCN-lesioned host brain, and the other a neuritic afferent outgrowth into the brain. There is, moreover, doubt about the integration of the ‘new’ SCN in terms of afferent input. Given the fact that the in situ SCN has an extensive efferent and afferent system in the intact brain, the SCN grafting experiments seem to indicate that only limited aspects of the SCN can drive circadian physiological rhythms. However, on the basis of current knowledge on grafting results the present paper recommends performing more sophisticated SCN grafting experiments to contribute to the knowledge on the SCN clock system.     

Melanic moths and charges in epiphytic vegetation in north-west England and north Wales

In 1973 the appearance and epiphyte cover of tree trunks was examined along a 125 km cline of melanic frequency in the peppered moth in NW England and N Wales. The sampled sites were resurveyed in 1986. There has been a marked increase in the crustose lichen Lecanora conizaeoides at the eastern end of the transect, an increase in lichen diversity in the middle of the transect and a possible decline in large foliose forms at the western end. These changes are discussed in relation to the eastward shift of the cline in melanic frequencies in the moth.     

When assumptions on visual system evolution matter: nestling colouration and parental visual performance in birds

Comparative studies in visual ecology of birds often rely on several assumptions on the evolution of avian vision. In this study, we show that when these assumptions are not upheld, conclusions may be strongly affected. To illustrate this purpose, we reanalysed the data of Avilés & Soler (J. Evol. Biol. 22 : 376–386, 2009) who demonstrated that nestling gape colouration in altricial birds is associated with visual system. We show that a slight change in analysis methodology leads to opposite conclusions. Such conflicting result raises the problem of applying powerful methods developed for continuous variables to a small sample and a small number of independent events of qualitative visual system shift in comparative analyses. Further, we show that the current trend to assume strong phylogenetic inertia of avian visual systems is contradicted by data and that the sequencing of the SWS1 opsin gene should be considered as an alternative approach.     

Habituation to a danger stimulus in two semiterrestrial crabs: ontogenic,ecological and opioid modulation correlates

Previous research on the habituation of the crab Chasmagnathus granulatus to an iterated visual danger stimulus disclosed two remarkable features of this mnemonic process: a) the ready acquisition and long-lasting nature of the habituated response, and b) the likely endogenous opioid modulation of the shortterm habituation, whose potential adaptive value was studied here. Both the habituation ability and the opioid modulation of such ability were analysed in Chasmagnathus granulatus and Pachygrapsus marmoratus, two closely related grapsid species that diverge widely in ecology. Results indicate that Chasmagnathus has a much greater capacity to habituate than Pachygrapsus, showing a more pronounced short-term habituation which seems to some extent mediated by an endogenous opioid mechanism, and a faster acquisition of a greater longterm habituation partially mediated by memorial representation of the contextual cues. A correlation between these differences and those related with the ecological pressure was discussed. The capacity of acquiring longterm habituation in crabs of the same species but different age was also assessed, showing that old animals clearly exhibit lower retention of the habituated response than young crabs. The possible correlation between this age-dependent change and an ontogenetic shift of habitat was discussed.     

Local adaptation and divergence in colour signal conspicuousness between monomorphic and polymorphic lineages in a lizard

Population differences in visual environment can lead to divergence in multiple components of animal coloration including signalling traits and colour patterns important for camouflage. Divergence may reflect selection imposed by different receivers (conspecifics, predators), which depends in turn on the location of the colour patch. We tested for local adaptation of two genetically and phenotypically divergent lineages of a rock‐inhabiting lizard, Ctenophorus decresii, by comparing the visual contrast of colour patches to different receivers in native and non‐native environments. The lineages differ most notably in male throat coloration, which is polymorphic in the northern lineage and monomorphic in the southern lineage, but also differ in dorsal and lateral coloration, which is visible to both conspecifics and potential predators. Using models of animal colour vision, we assessed whether lineage‐specific throat, dorsal and lateral coloration enhanced conspicuousness to conspecifics, increased crypsis to birds or both, respectively, when viewed against the predominant backgrounds from each lineage. Throat colours were no more conspicuous against native than non‐native rock but contrasted more strongly with native lichen, which occurs patchily on rocks inhabited by C. decresii. Conversely, neck coloration (lateral) more closely matched native lichen. Furthermore, although dorsal coloration of southern males was consistently more conspicuous to birds than that of northern males, both lineages had similar absolute conspicuousness against their native backgrounds. Combined, our results are consistent with local adaptation of multiple colour traits in relation to multiple receivers, suggesting that geographic variation in background colour has influenced the evolution of lineage‐specific coloration in C. decresii.     

An Effective Method for Detection and Analysis of DNA Damage Induced by Heavy-Ion Beams

We have developed an efficient system to detect and analyze DNA mutations induced by heavy-ion beams in Arabiopsis thaliana. In this system, a stable transgenic Arabidopsis line that constitutively expresses a yellow fluorescent protein (YFP) by a single-copy gene at a genomic locus was constructed and irradiated with heavy-ion beams. The YFP gene is a target of mutagenesis, and its loss of function or expression can easily be detected by the disappearance of YFP signals in planta under microscopy. With this system, a ¹²C⁶⁺-induced mutant with single deletion and multiple base changes was isolated.     

Rhodopsin photoproducts in 2D crystals

The published electron microscope and X-ray structures of rhodopsin have made available a detailed picture of the inactive dark state of rhodopsin. Yet, the photointermediates of rhodopsin that ultimately lead to the activated receptor species still await a similar analysis. Such an analysis first requires the generation and characterization of the photoproducts that can be obtained in crystals of rhodopsin. We therefore studied with Fourier-transform infrared (FTIR) difference spectroscopy the photoproducts in 2D crystals of bovine rhodopsin in a p22(1)2(1) crystal form. The spectra obtained by cryotrapping revealed that in this crystal form the still inactive early intermediates batho, lumi, and meta I are similar to those obtained from rhodopsin in native disk membranes, although the transition from lumi to meta I is shifted to a higher temperature. However, at room temperature, the formation of the active state, meta II, is blocked in the crystalline environment. Instead, an intermediate state is formed that bears some features of meta II but lacks the specific conformational changes required for activity. Despite being unable to activate its cognate G protein, transducin, to a significant extent, this intermediate state is capable of interacting with functional transducin-derived peptides to a limited extent. Therefore, while unable to support formation of rhodopsin's active state meta II, 2D p22(1)2(1) crystals proved to be very suitable for determining 3D structures of its still inactive precursors, batho, lumi, and meta I. In future studies, FTIR spectroscopy may serve as a sensitive assay to screen crystals grown under altered conditions for potential formation of the active state, meta II.     

Effect of Sahaja Yoga Meditation on Auditory Evoked Potentials (AEP) and Visual Contrast Sensitivity (VCS) in Epileptics

The effect of Sahaja yoga meditation on 32 patients with primary idiopathic epilepsy on regular and maintained antiepileptic medication was studied. The patients were randomly divided into 3 groups: group I practiced Sahaja Yoga meditation twice daily for 6 months under proper guidance; group II practiced postural exercises mimicking the meditation for the same duration; and group III was the control group. Visual Contrast Sensitivity (VCS), Auditory Evoked Potentials (AEP), Brainstem Auditory Evoked Potentials (BAEP), and Mid Latency Responses (MLR) were recorded initially (0 month) and at 3 and 6 months for each group. There was a significant improvement in VCS following meditation practice in group I participants. Na, the first prominent negative peak of MLR and Pa, the positive peak following Na did not register changes in latency. The Na-Pa amplitude of MLR also showed a significant increase. There were no significant changes in the absolute and interpeak latencies of BAEP. The reduced level of stress following meditation practice may make patients more responsive to specific stimuli. Sahaja Yoga meditation appears to bring about changes in some of the electrophysiological responses studied in epileptic patients.