Spider Movement, UV Reflectance and Size, but Not Spider Crypsis, Affect the Response of Honeybees to Australian Crab Spiders

According to the crypsis hypothesis, the ability of female crab spiders to change body colour and match the colour of flowers has been selected because flower visitors are less likely to detect spiders that match the colour of the flowers used as hunting platform. However, recent findings suggest that spider crypsis plays a minor role in predator detection and some studies even showed that pollinators can become attracted to flowers harbouring Australian crab spider when the UV contrast between spider and flower increases. Here we studied the response of Apis mellifera honeybees to the presence of white or yellow Thomisus spectabilis Australian crab spiders sitting on Bidens alba inflorescences and also the response of honeybees to crab spiders that we made easily detectable painting blue their forelimbs or abdomen. To account for the visual systems of crab spider's prey, we measured the reflectance properties of the spiders and inflorescences used for the experiments. We found that honeybees did not respond to the degree of matching between spiders and inflorescences (either chromatic or achromatic contrast): they responded similarly to white and yellow spiders, to control and painted spiders. However spider UV reflection, spider size and spider movement determined honeybee behaviour: the probability that honeybees landed on spider-harbouring inflorescences was greatest when the spiders were large and had high UV reflectance or when spiders were small and reflected little UV, and honeybees were more likely to reject inflorescences if spiders moved as the bee approached the inflorescence. Our study suggests that only the large, but not the small Australian crab spiders deceive their preys by reflecting UV light, and highlights the importance of other cues that elicited an anti-predator response in honeybees

Elevated arousal at time of decision-making is not the arbiter of risk avoidance in chickens

The somatic marker hypothesis proposes that humans recall previously experienced physiological responses to aid decision-making under uncertainty. However, little is known about the mechanisms used by non-human animals to integrate risk perception with predicted gains and losses. We monitored the behaviour and physiology of chickens when the choice between a high-gain (large food quantity), high-risk (1 in 4 probability of receiving an air-puff) option (HGRAP) or a low-gain (small food quantity), no-risk (of an air-puff) (LGNAP) option. We assessed when arousal increased by considering different stages of the decision-making process (baseline, viewing, anticipation, reward periods) and investigated whether autonomic responses influenced choice outcome both immediately and in the subsequent trial. Chickens were faster to choose and their heart-rate significantly increased between the viewing and anticipation (post-decision, pre-outcome) periods when selecting the HGRAP option. This suggests that they responded physiologically to the impending risk. Additionally, arousal was greater following a HGRAP choice that resulted in an air-puff, but this did not deter chickens from subsequently choosing HGRAP. In contrast to human studies, we did not find evidence that somatic markers were activated during the viewing period, suggesting that arousal is not a good measure of avoidance in non-human animals

Do Queens of Bumblebee Species Differ In Their Choice Of Flower Colour Morphs Of Corydalis Cava (Fumariaceae)?

International audienceAbstractBumblebee queens require a continuous supply of flowering food plants from early spring for the successful development of annual colonies. Early in spring, Corydalis cava provides essential nectar and pollen resources and a choice of flower colour. In this paper, we examine flower colour choice (purple or white) in C. cava and verify the hypothesis that bumblebee queens differ in their choice of flower colour. A total of 10,615 observations of flower visits were made in spring 2011 and spring 2014 near Poznań, western Poland. Our results suggest that Bombus lucorum/cryptarum used purple flowers less, while Bombus terrestris used purple flowers more and Bombus hortorum showed no preference. Therefore, the colour morphs of C. cava are probably co-evolutionary adaptations to the development of another part of the insect community which has different colour preferences

Effect of invader removal: pollinators stay but some native plants miss their new friend

Removal of invasive species often benefits biological diversity allowing ecosystems’ recovery. However, it is important to assess the functional roles that invaders may have established in their new areas to avoid unexpected results from species elimination. Invasive animal-pollinated plants may affect the plant–pollination interactions by changing pollinator availability and/or behaviour in the community. Thus, removal of an invasive plant may have important effects on pollinator community that may then be reflected positive or negatively on the reproductive success of native plants. The objective of this study was to assess the effect of removing Oxalis pescaprae, an invasive weed widely spread in the Mediterranean basin, on plant–pollinator interactions and on the reproductive success of co-flowering native plants. For this, a disturbed area in central Portugal, where this species is highly abundant, was selected. Visitation rates, natural pollen loads, pollen tube growth and natural fruit set of native plants were compared in the presence of O. pes-caprae and after manual removal of their flowers. Our results showed a highly resilient pollination network but also revealed some facilitative effects of O. pes-caprae on the reproductive success of co-flowering native plants. Reproductive success of the native plants seems to depend not only on the number and diversity of floral visitors, but also on their efficiency as pollinators. The information provided on the effects of invasive species on the sexual reproductive success of natives is essential for adequate management of invaded areas.This work is financed by FEDER funds through the COMPETE Program and by Portuguese Foundation for Science and Technology (FCT) funds in the ambit of the project PTDC/ BIA-BIC/110824/2009, by CRUP Acc¸o˜es Integradas Luso- Espanholas 2010 with the project E10/10, by MCI-Programa de Internacionalizacio´n de la I ? D (PT2009-0068) and by the Spanish DGICYT (CGL2009-10466), FEDER funds from the European Union, and the Xunta de Galicia (INCITE09- 3103009PR). FCT also supported the work of S. Castro (FCT/ BPD/41200/2007) and J. Costa (CB/C05/2009/209; PTDC/ BIA-BIC/110824/2009). The work of V. Ferrero was supported by the Fundacio´n Ramo´n Areces

Migration control: A distance compensation strategy in ants

©The Author(s) 2016. This article is published with open access at Springerlink.com. Migratory behaviour forms an intrinsic part of the life histories of many organisms but is often a high-risk process. Consequently, varied strategies have evolved to negate such risks, but empirical data relating to their functioning are limited. In this study, we use the model system of the househunting ant Temnothorax albipennis to demonstrate a key strategy that can shorten migration exposure times in a group of social insects. Colonies of these ants frequently migrate to new nest sites, and due to the nature of their habitat, the distances over which they do so are variable, leading to fluctuating potential costs dependent on migration parameters. We show that colonies of this species facultatively alter the dynamics of a migration and so compensate for the distance over which a given migration occurs. Specifically, they achieve this by modulating the rate of ‘tandem running’, in which workers teach each other the route to a new nest site. Using this method, colonies are able to engage a larger number of individuals in the migration process when the distance to be traversed is greater, and furthermore, the system appears to be based on perceived encounter rate at the individual level. This form of decentralised control highlights the adaptive nature of a behaviour of ecological importance, and indicates that the key to its robustness lies in the use of simple rules. Additionally, our results suggest that such coordinated group reactions are central to achieving the high levels of ecological success seen in many eusocial organisms

Insect Bio-inspired Neural Network Provides New Evidence on How Simple Feature Detectors Can Enable Complex Visual Generalization and Stimulus Location Invariance in the Miniature Brain of Honeybees

This work was supported by a Human Frontier Science Program Grant RGP0022/2014 to LC and Queen Mary University of London Scholarship to MR. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

The p75 neurotrophin receptor is expressed by adult mouse dentate progenitor cells and regulates neuronal and non-neuronal cell genesis

<p>Abstract</p> <p>Background</p> <p>The ability to regulate neurogenesis in the adult dentate gyrus will require further identification and characterization of the receptors regulating this process. <it>In vitro </it>and <it>in vivo </it>studies have demonstrated that neurotrophins and the p75 neurotrophin receptor (p75^NTR) can promote neurogenesis; therefore we tested the hypothesis that p75^NTRis expressed by adult dentate gyrus progenitor cells and is required for their proliferation and differentiation.</p> <p>Results</p> <p>In a first series of studies focusing on proliferation, mice received a single BrdU injection and were sacrificed 2, 10 and 48 hours later. Proliferating, BrdU-positive cells were found to express p75^NTR. In a second series of studies, BrdU was administered by six daily injections and mice were sacrificed 1 day later. Dentate gyrus sections demonstrated a large proportion of BrdU/p75^NTRco-expressing cells expressing either the NeuN neuronal or GFAP glial marker, indicating that p75^NTRexpression persists at least until early stages of maturation. In p75^NTR(-/-) mice, there was a 59% decrease in the number of BrdU-positive cells, with decreases in the number of BrdU cells co-labeled with NeuN, GFAP or neither marker of 35%, 60% and 64%, respectively.</p> <p>Conclusions</p> <p>These findings demonstrate that p75^NTRis expressed by adult dentate progenitor cells and point to p75^NTRas an important receptor promoting the proliferation and/or early maturation of not only neural, but also glial and other cell types.</p

Relative Role of Flower Color and Scent on Pollinator Attraction: Experimental Tests using F1 and F2 Hybrids of Daylily and Nightlily

The daylily (Hemerocallis fulva) and nightlily (H. citrina) are typical examples of a butterfly-pollination system and a hawkmoth-pollination system, respectively. H. fulva has diurnal, reddish or orange-colored flowers and is mainly pollinated by diurnal swallowtail butterflies. H. citrina has nocturnal, yellowish flowers with a sweet fragrance and is pollinated by nocturnal hawkmoths. We evaluated the relative roles of flower color and scent on the evolutionary shift from a diurnally flowering ancestor to H. citrina. We conducted a series of experiments that mimic situations in which mutants differing in either flower color, floral scent or both appeared in a diurnally flowering population. An experimental array of 6×6 potted plants, mixed with 24 plants of H. fulva and 12 plants of either F1 or F2 hybrids, were placed in the field, and visitations of swallowtail butterflies and nocturnal hawkmoths were recorded with camcorders. Swallowtail butterflies preferentially visited reddish or orange-colored flowers and hawkmoths preferentially visited yellowish flowers. Neither swallowtail butterflies nor nocturnal hawkmoths showed significant preferences for overall scent emission. Our results suggest that mutations in flower color would be more relevant to the adaptive shift from a diurnally flowering ancestor to H. citrina than that in floral scent

Toxic but Drank: Gustatory Aversive Compounds Induce Post-ingestional Malaise in Harnessed Honeybees

BACKGROUND: Deterrent substances produced by plants are relevant due to their potential toxicity. The fact that most of these substances have an unpalatable taste for humans and other mammals contrasts with the fact that honeybees do not reject them in the range of concentrations in which these compounds are present in flower nectars. Here we asked whether honeybees detect and ingest deterrent substances and whether these substances are really toxic to them. RESULTS: We show that pairing aversive substances with an odor retards learning of this odor when it is subsequently paired with sucrose. Harnessed honeybees in the laboratory ingest without reluctance a considerable volume (20 µl) of various aversive substances, even if some of them induce significant post-ingestional mortality. These substances do not seem, therefore, to be unpalatable to harnessed bees but induce a malaise-like state that in some cases results in death. Consistently with this finding, bees learning that one odor is associated with sugar, and experiencing in a subsequent phase that the sugar was paired with 20 µl of an aversive substance (devaluation phase), respond less than control bees to the odor and the sugar. Such stimulus devaluation can be accounted for by the malaise-like state induced by the aversive substances. CONCLUSION: Our results indicate that substances that taste bitter to humans as well as concentrated saline solutions base their aversive effect on the physiological consequences that their ingestion generates in harnessed bees rather than on an unpalatable taste. This conclusion is only valid for harnessed bees in the laboratory as freely-moving bees might react differently to aversive compounds could actively reject aversive substances. Our results open a new possibility to study conditioned taste aversion based on post-ingestional malaise and thus broaden the spectrum of aversive learning protocols available in honeybees