Cuticular chemistry of the stingless bee Tetragonisca angustula

WALTER M FARINA; ANDRÉS GONZÁLEZ; MARÍA SOL BALBUENA

Congreso; 1st join meeting ISCE/ALAEQ; 2016

In social insects, nestmate and task-related recognition play an important role in the coordination and cohesion between members of the colony. We focused our study on the stingless bee Tetragonisca angustula, unique among social bees because present physical worker subcastes1. These bees have a sophisticated system of defense involving two complementary groups of guards: hovering guards (suspended in the air close to the hive entrance) and standing guards (stand on the inner or outer surface of the entrance tube). We identified, quantified and compared the cuticular compounds of worker bees performing different tasks: in-hive bees, foragers and guards. In-hive bees were captured directly from inside the hive. Foragers were trained to an artificial feeder and collected while feeding. The two groups of guard bees were collected at the hive entrance. Bees in all groups were frozen immediately after capture. Cuticular compounds were extracted by immersing the individuals in dichloromethane, and later analyzed using gas chromatography-mass spectrometry (GC-MS). We identified that in addition to hydrocarbons (CHCs), cuticular extracts contained small amounts of fatty acids, and abundant diterpenes and triterpenes that remain to be characterized. Among the CHCs, we found a mixture of normal saturated hydrocarbons with uneven carbon chains (C25, C27, C28, C31), along with minor amounts of methyl branched, mono- and di- unsaturated hydrocarbons. The amounts of CHCs were quantified relative to an internal standard, and compared statistically by Principal Components Analysis (PCA). We found significant differences in the relative abundance of CHCs between behavioral groups. Hive bees present low amounts of alkanes relative to outside groups while guards present high amounts of branched saturated hydrocarbons. Differential CHC profiles associated with behavioral groups could imply a mechanism for the recognition of nestmates of different subcastes.