Biomedical subjects

Rodrigo J De Marco

Publications and source records attributed to Rodrigo J De Marco.

5 recordsLinked to original sources

PubMed2006

Spatial memory, navigation and dance behaviour in Apis mellifera.

Navigation and dance communication in Apis mellifera have been extensively studied on the level of sensory processing, but the structure and content of the spatial memory underlying such phenomena have yet to be addressed. Here we survey new findings indicating that the memory used by bees to navigate within the range of their orientation flights is much more complex than hitherto thought. It appears to allow them to decide between at least two goals in the field, and to steer towards them over considerable distances. Two models concerning the structure of bees' spatial memory are developed from new empirical evidence. The first one relies on the integration of at least two flight vectors, while the second assumes the existence of a 'functional' map based on the information available on-site. These findings also raise questions about the process of encoding and decoding information in the context of the waggle dance. We review published data and recent evidence indicating that memories of topographical features might also be involved in dance communication, and point out what needs to be addressed to elucidate the corresponding memory demands. The flight paths of recruited bees can now be traced by means of radar techniques, and thus tools are available to tackle these questions.

Animal Communication↗

PubMed2006

Apis mellifera bees acquire long-term olfactory memories within the colony.

Early studies indicate that Apis mellifera bees learn nectar odours within their colonies. This form of olfactory learning, however, has not been analysed by measuring well-quantifiable learning performances and the question remains whether it constitutes a 'robust' form of learning. Hence, we asked whether bees acquire long-term olfactory memories within the colony. To this end, we used the bee proboscis extension response. We found that within-the-nest bees do indeed associate the odour (as the conditioned stimulus) with the sugar (as the unconditioned stimulus) present in the incoming nectar, and that the distribution of scented nectar within the colony allows them to establish long-term olfactory memories. This finding is discussed in the context of efficient foraging.

Animals↗

PubMed2006

How bees tune their dancing according to their colony's nectar influx: re-examining the role of the food-receivers' 'eagerness'.

Apis mellifera bees perform dances to communicate the presence of desirable nectar sources. The regulation of these dances does not depend exclusively on properties of the nectar sources, but also upon certain stimuli derived from the foraging status of the colony as a whole; i.e. bees exploiting a source of constant profitability are more likely to dance when the colony's nectar intake rate is low. Based on these stimuli, individual bees tune their dances according to their colony's nectar influx without visiting alternative nectar sources. Division of labour, in addition, is a common feature in honeybees. Upon returning to the nest, successful foragers transfer the content of their crops to food-receivers by means of a common behaviour in social insects called trophallaxis, i.e. the transfer of liquid food by mouth. Martin Lindauer stated that a returned forager may sense the foraging status of its colony on the basis of the food transfer process by computing how quickly and eagerly the food-receivers unload its crop. This study focuses on the forager's experience during the food transfer process, its variability based on the colony's nectar influx, and the separate effects that the 'ease' and the 'eagerness' of the food-unloading have on the tuning of recruitment dances. Results indicate that foragers can rapidly sense variations in the colony's nectar influx, even when they experience no variation in the time interval between their return to the hive and the beginning of the food transfer. To accomplish this task they appear to use stimuli derived from the number of food-receivers, which enable them, in turn, to set their dance thresholds in relation to the nectar influx of their colony. The relevance of these findings is discussed in the context of communication and successful foraging.

Animal Communication↗

PubMed2005

Does an increase in reward affect the precision of the encoding of directional information in the honeybee waggle dance?

Apis mellifera foragers perform waggle dances to communicate the presence of highly desirable nectar sources to their forager-mates. Each waggle dance consists of several waggle-runs (straight movements of the dancer closely aligned on the comb surface) that carry spatial information that the dance followers can use to locate the food source being advertised. To address how this complex motor display responds to unpredictable fluctuations in its main triggering stimulus, i.e., sucrose stimulation, we analyzed the effects of an increase in reward on the direction of consecutive waggle-runs as well as other components of the waggle dance. Results show that a sudden increase in reward may increase the directional scatter among consecutive waggle-runs, especially those performed at the beginning of the dance. However, a simultaneous and rapid increase in the duration of the signal--together with a more regular alignment of the later waggle-runs within the signal--seems to compensate the initial increase in directional scatter so that the transfer of directional information remains effective. These results point out that the regulation of dance maneuvers depends on the dancer's motivation to forage.

Animals↗

PubMed2005

Olfactory learning by means of trophallaxis in Apis mellifera.

Early reports indicate that trophallaxis, i.e. the exchange of liquid food by mouth, may allow honeybees to assign nectar odours with predictive values to anticipate biological meaningful reward stimuli. Nevertheless, this type of learning has not been addressed directly. In the present study, pairs of animals were isolated to induce trophallaxis under controlled conditions and, afterwards, the honeybee proboscis extension reflex was used to investigate the possible role of trophallaxis in learning olfactory cues. The results demonstrate unambiguously that associative learning actually occurs by means of trophallaxis. Animals associate the odour (as the conditioned stimulus or CS) and the sucrose (as the unconditioned stimulus or US) present in the solution they receive through trophallaxis. Moreover, this particular kind of learning leads to long-term olfactory memories after a single learning trial, even when trophallaxis is brief. In addition, we found that the strength of association is clearly affected by CS and US intensity as well as the recent previous foraging experiences of the animals. Comparisons are presented among several features of the learning during trophallaxis and the classical conditioning of the proboscis extension reflex with restrained subjects. Finally, the relevance of learning through trophallaxis in the task of successful foraging is discussed.

Analysis of Variance↗