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First published online September 15, 2004
Journal of Experimental Biology 207, 3693-3706 (2004)
Published by The Company of Biologists 2004
doi: 10.1242/jeb.01201

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Spatio-temporal patterns of antennal movements in the searching cockroach

Jiro Okada^* and Yoshihiro Toh

Department of Biology, Graduate School of Sciences, Kyushu University, Fukuoka 812-8581, Japan

View larger version (31K): [in a new window]   Fig. 1. Experimental apparatus for recording antennal movements. An animal was tethered on a free-moving Styrofoam ball to allow its unrestrained locomotion (Okada and Toh, 2000). Three video cameras were set just in front (1), top (2) and side (3) of the animal. Video images were processed by a 4-split multi-viewer, videotaped, and analyzed using a PC. Photograph on the right is an example of synthesized video frame after the processing, showing frontal (1), top (2) and side (3) views.

View larger version (31K): [in a new window]   Fig. 2. Method for measuring positions of the antenna, head and foreleg. (A) Top view (i) depicts horizontal angular positions of the right antenna and the foreleg, and yaw position of the head. Lateral view (ii) is a diagram for the antennal vertical and head pitch positions. (B) Relationships of parameters for the antennal (i) and head (ii) positions. Note that three-dimensional coordinates for antennal (i) and head (ii) positions are different from each other. The rostrocaudal y axis for the former is identical with the head axis, and the latter (y' axis) with the body axis. See Materials and methods for details of these parameters. O, origin for both antennal and head positions; O', origin for foreleg position; P, plotting point registering antennal position; P', plotting point registering foreleg position.

View larger version (52K): [in a new window]   Fig. 3. Antennal and head movements during pausing (A) and walking (B) in a searching cockroach. These two examples were obtained from the same animal. In pausing, large deflections were frequently observed in traces of the antennal horizontal components and the yaw and pitch components of the head (see shaded area). Antennal vertical arcs were lowered entirely in the walking state. Deflections in the head roll were relatively small in both behavioral states. Vertical calibration bars show angular positions for antennae and head. L, left; R, right.

View larger version (12K): [in a new window]   Fig. 4. Angular ranges and central positions for the horizontal and vertical components in both antennae and head. Bars and symbols indicate the mean angular ranges and central positions, respectively (N=10). Working ranges for antennal horizontal and head yaw components decreased, respectively, by about 25–30° and 15° during walking, but were not largely changed for antennal vertical and head pitch component s. Vertical central positions for both antennae were lowered by 15–25° during walking. R, right; L, left.

View larger version (38K): [in a new window]   Fig. 5. Power-spectra for antennal and leg movements in a searching cockroach. (A) Spectra for horizontal (H) and vertical (V) deflections in pausing. Their major peaks were distributed mainly at <3 Hz (H) and <4 Hz (V), respectively. (B) Power-spectra for antennal (H and V) and foreleg (L) movements in walking. Lower frequency components at <2 Hz were largely suppressed for horizontal deflections (H). Higher frequency components around 4 Hz became remarkable for vertical deflections (V) instead. Note that no conspicuous peak is observable in the H and V spectra at the frequency corresponding to major peaks in the L spectrum (2–3.5 Hz). Inset in each spectrum is part of the time course before FFT. These spectra were obtained from data for a 31 s period each.

View larger version (59K): [in a new window]   Fig. 6. Trajectories of both antennae and head. Data in cases 1–3 were obtained from three different animals. The sampling period for each graph was 15 s. The right and left antennal trajectories are indicated, respectively, by red and blue traces, and the head by green traces. (1) The random pattern was most commonly observed in both pausing (A) and walking (B). (2) The loop-like pattern was apparent only during walking. Insets in the right panel show typical examples of the three basic patterns forming the loop-like trajectory. These were derived from a trajectory of the left antenna. L, loop; A, arch; V, vertical line. (3) The `consistent' loop-like pattern independent of the searching mode.

View larger version (30K): [in a new window]   Fig. 7. Kinematics of the scape–pedicel (S–P) joint in two behavioral states. By immobilizing the head–scape (H–S) joints (see inset at bottom), movement of the S–P joint could be analyzed independently. (A) Trajectory patterns formed simple vertical lines in both pausing and walking. Vertical positions were lowered entirely by 20–30° during pausing. (B) Power-spectra for vertical components (V) in the two states. These spectra were obtained from the time-series whose trajectories are shown in A. Discrete peaks appear at 1.5–3.5 Hz during pausing, but distributed over a wider range up to 4.5 Hz in walking. (C) Spatial profiles of the S–P joints in pausing and walking. Bars and symbols indicate averages of the angular ranges and the central positions, respectively (N=4). Both antennae significantly lowered by about 25° during walking. Inset shows a rotation axis of the free S–P joint in this condition. Sampling periods were 30 s(trajectories) and 34 s (power-spectra). H, head; S, scape; P, pedicel; F, flagellum.

View larger version (29K): [in a new window]   Fig. 8. Kinematics of the head–scape (H–S) joint in two behavioral states. The S–P joint is immobilized in this condition (see inset at bottom). (A) Trajectories showed two-dimensional expansion in both states. During walking, both antennae concentrated at lower positions. (B) Power-spectra of horizontal (H) and vertical (V) components in the two states. Peaks at <2 Hz decreased in walking for both components. These spectra were obtained from the time-series whose trajectories are shown in A. (C) Mean angular ranges (bars) and central positions (symbols) of both antennae during pausing and walking (N=4). Vertical central positions for both antennae were significantly lowered as observed in the S–P joint free condition (see Fig. 7). Horizontal working ranges were slightly but significantly narrowed during walking. Inset indicates two rotation axes of the free H–S joint. Sampling periods and abbreviations, see Fig. 7.

View larger version (37K): [in a new window]   Fig. 9. Cross-correlations between right (R) and left (L) antennal movements during pausing. (A) Trajectories of both antennae show typical random patterns (sampling period 18 s). (B) Cross-correlation for horizontal components. The waves indicate the time courses of the right and left horizontal deflections for a period of 42 s. Note that polarities for the horizontal position are opposite between the right and left antennae (refer to calibration bars). RH, horizontal deflection of the right antenna; LH, horizontal deflection of the left antenna. Correlation coefficients (r) in the correlation map were calculated by reference to the left antenna. Significant positive correlations (r>0.25) are indicated by yellow to red, and the negative ones (r<–0.25) by blue to black. Significant negative correlations were observed as broad blue or black spots. Backgrounds filled by gray color represent the areas where r values were not statistically significant (|r|<0.25). (C) Cross-correlation for vertical components. Significant correlations were few on the map. RV, vertical deflection of the right antenna; LV, vertical deflection of the left antenna.

View larger version (40K): [in a new window]   Fig. 10. Cross-correlations between right and left antennal movements in walking. The data were from the same animal as in Fig. 9. (A) Trajectories of both antennae were still random, and their scanning areas were smaller than those seen during pausing (cf. Fig. 9A). (B) Cross-correlation for horizontal components. Significant negative correlations existed close to the zero time lag as relatively compact spreads along the ordinate (compare with Fig. 9B). Inset shows expansion of the boxed area (1). Though individual small waves did not exactly synchronize with each other, coordination is recognizable in both larger and slower components. (C) Cross-correlation for vertical components. Significant positive correlation spots were continuously observed over the map at zero time lag as sharp peaks. Expansion of the boxed area (2) shows synchronization of the pair of waves at 2–3 Hz. Note the time scale difference from Inset 1.