Life expectancy and onset of foraging in the honeybee (Apis mellifera) |
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Authors: | M Woyciechowski D Moroń |
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Institution: | (1) Institute of Environmental Sciences, Jagiellonian University, Gronostajowa 7, 30-387 Kraków, Poland;(2) Institute of Systematics and Evolution of Animals, Polish Academy of Sciences, Sławkowska 17, 31-016 Kraków, Poland |
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Abstract: | Predictions that precocious foraging in honeybee workers is a result of shortening of their life expectancy were tested in
both laboratory and field experiments. In the laboratory experiment, we assessed the impact of anaesthesia with CO2 and infection with Nosema apis on the lifespan of workers. In the field experiment, the age at onset of foraging was observed in groups of workers with
different expected lifespans. In both the experiments, workers originating from one queen inseminated with the semen of one
drone were divided into five groups. The first group was anaesthetized with CO2 on the first day of life. Workers from the other three groups were individually inoculated with a constant number of N. apis spores on the 1st, 6th and 11th days of life. Workers from the fifth control group were neither treated with CO2 nor inoculated in any way. Both the laboratory and field experiments revealed that anaesthetized and infected workers had
shorter expected lifespans compared to control bees. Amongst infected workers, those inoculated earlier in life survived for
a significantly shorter period of time in comparison to those infected later in life. In agreement with the expectation, the
field experiment showed that anaesthetized and infected workers with shorter expected lifespan start foraging earlier than
control workers. Amongst the infected workers, age at inoculation correlated with age at onset of foraging. This means that
short-lived workers complete safe nest tasks and begin riskier foraging earlier in life. Our results provide a strong support
for the hypothesis that the division of labour in eusocial insects is a consequence of the different expected worker lifespan
and different risk associated with their tasks; however, they do not contradict other existing explanations. |
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Keywords: | Apis mellifera Life expectancy Division of labour Division of risk Nosema apis |
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