Sensory basis for directional wind detection in first instar cockroaches,Periplaneta americana

Summary

• 1. First instarPeriplaneta americana have only two wind-receptive filiform hair sensilla on each cercus, as compared to over 200 on the cercus of an adult cockroach. The two hairs have preferential planes of deflection which are approximately at right angles to each other (Figs. 1, 2).

• 2. The responses of single sensory neurons associated with the hairs were recorded extracellularly from the cereal nerve with tungsten electrodes. Movement of a hair in one direction within its preferential plane depolarized the underlying neuron and elicited an increased frequency of action potentials. Deflection in the opposite direction hyperpolarized the cell and caused the cessation of ongoing activity (Fig. 3).

• 3. Receptive fields for wind in the horizontal plane were plotted for all four hairs. Although the fields were broadly tuned and overlapped each other considerably, each hair sensillum dominated one quadrant of horizontal space, and all 360 ° were covered by the four hairs (Fig. 4).

• 4. The escape behavior of first instar nymphs, which depends on these sensilla, was oriented away from a source which delivered small puffs of wind. The nymph's accuracy of directed turning was no less than that of adult animals (Fig. 5).

• 5. When various combinations of hairs were removed from the cerci, the animals could no longer make correctly oriented turns to wind from all angles. The turns they did make reflected the physiological receptive fields of the remaining hairs and suggested that the behavior is based, to some extend, on comparisons of impulse frequency among the four sensory afferents (Fig. 6).