Biomedical subjects

Jürgen Tautz

Publications and source records attributed to Jürgen Tautz.

11 recordsLinked to original sources

PubMed2006

The parasitic mite Varroa destructor affects non-associative learning in honey bee foragers, Apis mellifera L.

The parasitic mite Varroa destructor influences flight behavior, orientation and returning success of forager honeybees (Apis mellifera) infested as adults. As impaired orientation toward the nest entrance might be due to deficiency in recognition and responsiveness to stimuli in the environment, we examined effects of V. destructor on sensory responsiveness, non-associative and associative learning of honey bee foragers by using proboscis extension reaction paradigm (PER). Although infested and uninfested workers were initially equally responsive to different concentrations of sugar water, we found differences in non-associative learning. In habituation, PER to repeated sugar stimulation of the antennae occurred faster in infested foragers compared to uninfested foragers. In sensitization, infested foragers showed a lower response to an odor stimulus following sugar stimulation than non-infested foragers. Differences in non-associative paradigms were more pronounced in bees with lower responsiveness to sucrose. In conditioning learning experiments, a significant reduction in proboscis extension response was found 1 min but not 12 min after a single conditioning trial indicating that V. destructor predominantly affects the non-associative components of learning and its underlying neural and molecular processes.

Animals↗

PubMed2006

Beyond 9-ODA: sex pheromone communication in the European honey bee Apis mellifera L.

The major component of the mandibular gland secretion of queen honeybees (Apis mellifera L.), 9-ODA ((2E)-9-oxodecenoic acid), has been known for more than 40 yr to function as a long-range sex pheromone, attracting drones at congregation areas and drone flyways. Tests of other mandibular gland components failed to demonstrate attraction. It remained unclear whether these components served any function in mating behavior. We performed dual-choice experiments, using a rotating drone carousel, to test the attractiveness of 9-ODA compared to mixtures of 9-ODA with three other most abundant components in virgin queen mandibular gland secretions: (2E)-9-hydroxydecenoic acid (9-HDA), (2E)-10-hydroxydecenoic acid (10-HDA), and p-hydroxybenzoate (HOB). We found no differences in the number of drones attracted to 9-ODA or the respective mixtures over a distance. However, adding 9-HDA and 10-HDA, or 9-HDA, 10-HDA, and HOB to 9-ODA increased the number of drones making contact with the baited dummy. On the basis of these results, we suggest that at least 9-HDA and 10-HDA are additional components of the sex pheromone blend of A. mellifera.

Animal Communication↗

PubMed2006

Do honeybees detect colour targets using serial or parallel visual search?

In humans, visual search tasks are commonly used to address the question of how visual attention is allocated in a specific task and how individuals search for a specific object (;target') among other objects (;distractors') that vary in number and complexity. Here, we apply the methodology of visual search experiments to honeybees, which we trained to choose a coloured disc (target) among a varying number of differently coloured discs (distractors). We measured accuracy and decision time as a function of distractor number and colour. We found that for all colour combinations, decision time increased and accuracy decreased with increasing distractor number, whereas performance increased when more targets were present. These findings are characteristic of a serial search in primates, when stimuli are examined sequentially. We found no evidence for parallel search in bees, which would be characterized by a ;pop out' effect, in which the slope of decision time (and accuracy) over distractor number would be near zero. Additionally, we found that decision time and number of errors were significantly higher when bees had to choose a blue target among yellow distractors compared with the inverse colour combination, a phenomenon known as search asymmetry in humans.

Animals↗

PubMed2004

Egg viability and worker policing in honey bees.

In many species of social Hymenoptera, unmated workers can lay eggs that will produce males by parthenogenesis. Nevertheless, in queenright honey bee colonies (Apis mellifera), worker reproduction is low. One possible mechanism for this difference is worker policing, the removal of worker-laid eggs by other workers. This behavior can evolve in species in which queens are multiply mated, where workers are more closely related to the sons of their mother than those of their sisters. Another possible mechanism of the low level of worker reproduction is worker-laid eggs being less viable than queen-laid eggs. We show that this difference in quality is the case for honey bees.

Animals↗

PubMed2004

Synaptic organization in the adult honey bee brain is influenced by brood-temperature control during pupal development.

Recent studies have shown that the behavioral performance of adult honey bees is influenced by the temperature experienced during pupal development. Here we explore whether there are temperature-mediated effects on the brain. We raised pupae at different constant temperatures between 29 and 37 degrees C and performed neuroanatomical analyses of the adult brains. Analyses focused on sensory-input regions in the mushroom bodies, brain areas associated with higher-order processing such as learning and memory. Distinct synaptic complexes [microglomeruli (MG)] within the mushroom body calyces were visualized by using fluorophore-conjugated phalloidin and an antibody to synapsin. The numbers of MG were different in bees that had been raised at different temperatures, and these differences persisted after the first week of adult life. In the olfactory-input region (lip), MG numbers were highest in bees raised at the temperature normally maintained in brood cells (34.5 degrees C) and significantly decreased in bees raised at 1 degrees C below and above this norm. Interestingly, in the neighboring visual-input region (collar), MG numbers were less affected by temperature. We conclude that thermoregulatory control of brood rearing can generate area- and modality-specific effects on synaptic neuropils in the adult brain. We propose that resulting differences in the synaptic circuitry may affect neuronal plasticity and may underlie temperature-mediated effects on multimodal communication and learning.

Animals↗

PubMed2003

Thorough warm-up before take-off in honey bee swarms.

In a bivouacked swarm of honey bees, most individuals are quiescent while a small minority (the scouts) are active in choosing the swarm's future nest site. This study explores the way in which the members of a swarm warm their flight muscles for take-off when the swarm eventually decamps. An infrared camera was used to measure the thoracic (flight muscle) temperatures of individual bees on the surface of a swarm cluster. These are generally the coolest bees in a swarm. The warming of the surface-layer bees occurred mainly in the last 10 min before take-off. By the time a take-off began, 100% of the bees had their flight muscles heated to at least 35 degrees C, which is sufficient to support rapid flight. Take-offs began only a few seconds after all the surface-layer bees had their flight muscles warmed to at least 35 degrees C, but exactly how take-offs are triggered remains a mystery.

Animals↗

PubMed2003

Automatic life-long monitoring of individual insect behaviour now possible.

Automatic tracking and identification of individuals has the potential to revolutionize the study of insects, especially social insects, by opening up options for questions which could not be asked before. To achieve this we developed a reliable and cost-sensible RFID (Radio-Frequency Identification) based solution that automatically recognises a virtually unlimited number (18 x 10(18) possible ID numbers) of individual insects down to the size of bees and ants. The data are collected automatically for any desired time span (if interesting, up to the entire life of the individual), pre-processed and saved in a database for further analysis. The usage of database techniques allows parallel data processing with a virtually unlimited number of parameter connections. ID numbers can be linked to any simultaneously recorded parameters of interest, e.g. spatial and temporal information as shown here for a bumblebee colony.

Journal Article↗

PubMed2003

The spectral input to honeybee visual odometry.

Bees returning from a feeder placed in a narrow tunnel that is lined with a chequered pattern will strongly overestimate travel distance. This finding supports the view that their distance estimation is based on integrating optic flow experienced during flight. Here, we use chequered tunnels with various colour combinations as a tool to identify the spectral channel used by bees to gauge travel distance. The probability of bees performing waggle dances after a short travel distance correlates only with the low range of the green contrast of the pattern in the tunnel. But it does not correlate with the pattern's chromatic contrast or brightness contrast. Distance estimation is therefore colour blind. We also evaluated the waggle runs as a function of colour pattern. Their duration is the code for the food source distance. Waggle run duration is entirely independent of the colour pattern used, implying that once green contrast is above detection threshold, distance estimation depends solely on the angular motion of the landscape passed in flight.

Animal Communication↗

PubMed2003

Hot bees in empty broodnest cells: heating from within.

Honeybee colonies maintain brood nest temperatures of 33-36 degrees C. We investigated brood nest thermoregulation at the level of individual worker behaviour and the transfer of heat from workers to the brood. Worker bees contribute to the regulation of brood nest temperature by producing heat while sitting motionless on the caps of brood cells. We report here an additional, newly observed heating strategy where heating bees enter empty cells between sealed brood cells and remain there motionless for periods of up to 45 min. Individually marked worker bees on the surface of sealed brood cells maintained thorax temperatures (T(th)) between 32.2+/-1.0 degrees C and 38.1+/-2.5 degrees C (mean +/- S.D.; N=20 bees) with alternating warming and cooling periods. Most of the observed bees made one or several long-duration visits (>2 min) to empty cells within the sealed brood area. T(th) at the time bees entered a cell [T(th(entry))] was 34.1-42.5 degrees C (N=40). In 83% of these cell visits, T(th(entry)) was higher (up to 5.9 degrees C; mean 2.5+/-1.5 degrees C; N=33) than the mean T(th) of the same bee. High values of T(th(entry)) resulted from preceding heating activity on the comb surface and from warm-ups just prior to cell visits during which T(th) increased by up to +9.6 degrees C. Bees inside empty cells had mean T(th) values of 32.7+/-0.1 degrees C (resting bees) to 40.6+/-0.7 degrees C (heat-producing bees) during long-duration cell visits without performing any visible work. Heating behaviour inside cells resembles heating behaviour on the brood cap surface in that the bees appear to be inactive, but repeated warmings and coolings occur and T(th) does not fall below the optimum brood temperature. Bees staying still inside empty cells for several minutes have previously been considered to be 'resting bees'. We find, however, that the heating bees can be distinguished from the resting bees not only by their higher body temperatures but also by the continuous, rapid respiratory movements of their abdomens. By contrast, abdominal pumping movements in resting bees are discontinuous and interrupted by long pauses. Heat transfer to the brood from individual bees on the comb surface and from bees inside empty cells was simulated under controlled conditions. Heating on the comb surface causes a strong superficial warming of the brood cap by up to 3 degrees C within 30 min. Heat transfer is 1.9-2.6 times more efficient when the thorax is in touch with the brood cap than when it is not. Heating inside empty cells raises the brood temperature of adjacent cells by up to 2.5 degrees C within 30 min. Heat flow through the comb was detectable up to three brood cells away from the heated thorax.

Animals↗

PubMed2002

Hot spots in the bee hive.

Honeybee colonies (Apis mellifera) maintain temperatures of 35-36 degrees C in their brood nest because the brood needs high and constant temperature conditions for optimal development. We show that incubation of the brood at the level of individual honeybees is done by worker bees performing a particular and not yet specified behaviour: such bees raise the brood temperature by pressing their warm thoraces firmly onto caps under which the pupae develop. The bees stay motionless in a characteristic posture and have significantly higher thoracic temperatures than bees not assuming this posture in the brood area. The surface of the brood caps against which warm bees had pressed their thorax were up to 3.2 degrees C warmer than the surrounding area, confirming that effective thermal transfer had taken place.

Animals↗

PubMed2002

Worker piping triggers hissing for coordinated colony defence in the dwarf honeybee Apis florea.

Defending a large social insect colony containing several thousands of workers requires the simultaneous action of many individuals. Ideally this action involves communication between the workers, enabling coordinated action and a fast response. The Asian dwarf honeybee, Apis florea, is a small honeybee with an open nesting habit and a comparatively small colony size, features that leave them particularly exposed to predators. We describe here a novel defence response of these bees in which the emission of an initial warning signal from one individual ("piping") is followed 0.3 to 0.7 seconds later by a general response from a large number of bees ("hissing"). Piping is audible to the human ear, with a fundamental frequency of 384 +/- 31Hz and lasting for 0.82 +/- 0.35 seconds. Hissing is a broad band, noisy signal, clearly audible to the human observer and produced by slight but visible movements of the bees' wings. Hissing begins in individuals close to the piping bee, spreads rapidly to neighbours and results in an impressive coordinated crescendo occasionally involving the entire colony. Piping and hissing are accompanied by a marked decrease, or even cessation, of worker activities such as forager dancing and departures from the colony. We show that whereas hissing of the colony can be elicited without piping, the sequential and correlated piping and hissing response is specific to the presence of potential predators close to the colony. We suggest that the combined audio-visual effect of the hissing might deter small predators, while the cessation of flight activity could decrease the risk of predation by birds and insects which prey selectively on flying bees.

Journal Article↗