Honeybees are able to represent very high flow-rates through trophallactic food-exchange contacts

WAINSELBOIM, ALEJANDRO JAVIER; FARINA, WALTER MARCELO

Göttingen, Alemania

Congreso; 26th Göttingen Neurobiology Conference; 1998

Honeybee foragers collecting nectar reach different crop loads depending on the sucrose flow delivered by the food source (Núñez, 1966. Z. vergl. Physiol. 53, 142-164). However, this relationship is found only within a certain range of sucrose flow exploited at nectar sources. For flow rates higher than 5 mg of sugar per minute, foragers attain maximal crop loads (approx. 65 µl), independently of sugar concentration. Once the foraging visit is complete, bees arrive at the hive and unload their nectar crop load to fellow hive-mates by means of mouth to mouth exchange contacts (trophallaxis). It has been shown that the rate at which the collected liquid is transferred to the recipient animals depends on the sucrose flow present at the feeding site (Wainselboim & Farina, 1997, in preparation). Therefore it was suggested that transfer rate modulation depends on the degree of abdominal distension (abdominal volume), which in turn is determined by the sucrose flow of the exploited food source. This implies that bees are able to detect the sucrose flow while ingesting the offered solution and to represent the source’s profitability in these terms once in the hive, yet the range of sucrose flow detection and representation is still unknown.  In order to address this question, donor honeybees were offered 50% w/w (1.8 M) sucrose solution at either 10.1; 20.6 or 40.0 mg/min by means of a regulated flow artificial feeder. Trophallactic contacts were recorded inside an experimental arena between the satiated donor bee and an unfed recipient bee.   Even though time spent ingesting solution at the feeder decreased significantly with increasing flow, bees attained maximum crop loads with either three (Fig. 1A). Trophallactic transfer rate was found to increase along with the flow rate presented at the feeder (Fog. 1B).              These results give behavioural evidence suggesting bees are both capable of detecting sucrose flow rates and representing them within a far wider range than previously considered. It also suggests that trophallactic transfer rate does not depend on abdominal volume, for even when all bees attained similar maximal loads, transfer rate increased along with the offered sucrose flow. An interesting question opens, concerning the nature of the neurological basis underlying sucrose flow detection both at peripheral and central levels.