Honey Bee Foraging Dances Karl von Frisch Munich, Germany 1940’s

Foraging in bees Foraging behavior of bees changes over developmental time.

What is the genetic and molecular basis for this change in behavior? Researchers used microarray technology to ask how the expression of the genome changed over time, specifically between the nursing and foraging phases About 1/3 of examined genes were found to change their expression over time Does this rule out environmental signaling events in determining foraging behavior?

Microarray results

Juvenile hormone High in foragers, low in nurses Experimentally manipulate: Treat young bees with JH, they start foraging early Knockout the gland that produces JH, they never forage JH replacement therapy can restore foraging What controls JH? Age dependent gene-environment interactions Social cues/behavioral interactions

Behavioral interactions influence gene expression In colonies of uniform age, young nurses have no contact with older foragers, and a greater proportion of them develop precocious foraging behavior. Addition of older bees to the colony inhibits this phenotype, suggesting that exposure to some cue from foragers INHIBITS foraging (onset of JH) in young nurse bees. The cue has been identified as ethyl oleate.

The for gene

The for gene: DQ Devise an experiment to distinguish between the possibilities that 1) for simply increases with age and 2) for is essential for the transition to leaving the hive to collect pollen. Can your hypothesis integrate gene and social factors that mediate this switch?

Homologs of for in other species C. elegans egl-4 Roaming or dwelling Drosophila for Roving or sitting (larvae) Human PKG

Why we study honey bee dances Why do bees “dance”? How did “dancing” evolve and change over time? What is the adaptive value of such a complex behavior? What can we learn about neural processing and circuits?

Who performs Female worker bees leave the hive, forage for pollen or nectar, bring it back to the hive Return recruits other workers to gather around Movement Buzzing of wings Scent of flowers Pheromone

Why are dances performed? Convey information about where the pollen is Distance from hive Direction from hive Round dance: food is close Waggle dance: food is far, >50m Watchers imitate the dance, presumably as a way to learn the information provided

The round dance

The waggle dance The waggle dance performed in on a lit horizontal surface allows the dancer to just line up with the angle of the sun. In the dark hive, the direction of the sun is the vertical. If the hive is laid on its side and gravity cannot be used to orient the dance, workers will not be recruited.

How good are the dancers? Scouts trained to go to “F”, where most new bees arrived. All other feeding stations had equally attractive food, but fewer bees went to them, indicating they listen to the scouts Scouts trained to go to a feeder 750m from the hive, then new bees were collected at feeders placed at various distances from the hive. Majority were found closest to 750m, again showing that the distance information from the scouts was accurate and was interpreted by the new bees.

DQ Bees learn the location of a good food source and go to it. But food sources may become depleted. In this experiment, the bees were trained to go to a feeder that was subsequently removed. The flight path of the bees was tracked by radar. Describe the bees flight path(s). How can you know whether this response is adaptive?

How do bees measure distance? The scout passed through a narrow tunnel to get to the flowers which were only about 6m away, but she returned and danced the information that the flowers were 70m away. Bees flocked to the feeder located 70m away, again demonstrating that the follower workers listen to the scout. But why did the scout think the food was so far away? The increased visual stimulation from being in the tunnel apparently was more in line with a long journey because objects were so close.

Foragers send sound information through the air Returning foragers vibrate their wings causing changes in local air pressure that are detected by nearby bees Observers also use sound vibrations to signal the forager They vibrate their chest against the hive, which actually produces small shakes to the hive This indicates they want the forager to stop dancing and give out samples of the pollen or nectar she collected Thus, these two auditory signals do not drown each other out

Wing vibration is essential for recruitment of workers Foragers with clipped wings fly and dance normally, but do not recruit followers “diminutive” winged mutants also fly and forage and dance normally but do not recruit workers to the food source

Both sound and movement are required (robot dancer)

Bees have ears and hear well in the frequency associated with the dancing

Proving bees can hear Aversive learning Reinforcement Pair a CS, a low frequency air vibration similar to the waggle dance sound, with electric shock (US) Measure CR, whether the bee will leave the tube upon hearing the sound before the shock Yes, they learn, but slowly Proves they can hear the sound Reinforcement Y shaped maze, play a sound from one arm, reward bee with sugar water if she turns toward it Bees quickly learn to turn toward the arm with the sound

Johnston’s Organ Located in the second joint of the antenna Chordotonal organ similar to mosquitos

Ai et al 2007

DL-1 interneuron in dorsal lobe (receives synapse from JO) When the basal firing rate is low, vibrational stimuli cause a phasic firing rate. When the basal rate is high, vibration causes tonic inhibition Ai et al 2009

Odor may act to sensitize the DL-1 interneuron to vibration—the tonic inhibition is stronger when the prior firing rate is high. Modest firing as seen in B leads to phasic response when vibration is added.