Chemosensory reception and task division in stingless bees
The relationship between chemosensory abilities and task division has been poorly studied in stingless bees. I examined odor reception and sugar responsiveness of the social stingless bee Tetragonisca angustula, focusing on workers involved in different tasks. Using the proboscis extension response, I evaluated sucrose response thresholds (SRTs) of foragers and guards. Additionally, I studied the response thresholds of foragers to glucose and fructose. Peripheral responses to odors at the antennae of foragers and guards were recorded by electroantennography (EAG). Besides, I quantified and described the number and type of sensilla present on the antennae of those bee groups using scanning electron microscopy. I found that foragers’ SRTs changed according to the resource collected: nonpollen foragers (NPF) showed higher SRTs than pollen foragers (PF) and guards, which showed similar sucrose responsiveness. Also, pollen foragers showed different response thresholds according to the type of sugar offered (sucrose > glucose > fructose), while both NPF and PF presented a lower response to fructose compared to sucrose and glucose. EAG signal strength of both foragers and guards increased with increasing odor concentration. Interestingly, guard bees showed the highest response to citral, an odor that triggers defensive behavior in T. angustula. The type and number of sensilla present in the antennae of guards and foragers were similar. These results suggest that differences found in chemosensory responses among worker subcastes are task dependent and might be involved in regulating the division of labor.
Laboratorio de Insectos Sociales, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina.