BIOPHYSICS OF THE SUBGENUAL ORGAN OF THE HONEYBEE, APIS-MELLIFERA

The subgenual organ of the honeybee (Apis mellifera) is suspended in a haemolymph channel in the tibia of each leg. When the leg is accelera ted, inertia causes the haemolymph (and the subgenual organ) to lag be hind the movement of the rest of the leg. The magnitude of this phase lag determines the displacement of the subgenual organ relative to the leg and to the proximal end of the organ, which is connected to the c uticle. Oscillations of the subgenual organ are visualised during vibr ation stimulation of the leg, by means of stroboscopic light. Video an alysis provides fairly accurate values of the amplitude and phase of t he oscillations, which are compared with the predictions of a model. T he model comparison shows that the haemolymph channel can be described as an oscillating fluid-filled tube occluded by an elastic structure (probably the subgenual organ). The mechanical properties of the subge nual organ and haemolymph channel resemble those of an overdamped mass -spring system. A comparison of the threshold curve of the subgenual o rgan determined using electrophysiology with that predicted by the osc illating tube model suggests that the sensory cells respond to displac ements of the organ relative to the leg.