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First published online January 19, 2006
Journal of Experimental Biology 209, 567-575 (2006)
Published by The Company of Biologists 2006
doi: 10.1242/jeb.02020

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Corners and bubble wrap: the structure and texture of surfaces influence crayfish exploratory behaviour

B. W. Patullo^* and D. L. Macmillan

Department of Zoology, University of Melbourne, Parkville, VIC, 3010, Australia

View larger version (16K): [in a new window]   Fig. 1. The peg-board system used to erect different configurations of walls. (A) Grooves were cut into the acrylic base plate so that supports could be positioned. Grey lines on base indicate scratched surface for traction. (B) Walls were attached by a clip at the top. Spacers were placed between the support and wall in the laneway configuration to standardise the width to 65 mm. (C) An example of one of the configurations of walls (straight) during a trial. Cameras were fixed to a tripod and suspended over a wall. Two cameras with overlapping fields were used over long walls, as shown. Footage was previewed on a monitor and recorded on video cassette recorder (VCR). Weights held the base plate to the bottom of the large tank (not shown). (D) Plan views of the five wall arrangements for the two experiments. Configurations are, from top to bottom: straight wall middle release (1), straight wall end release (2), corner (3), square (4) and laneway (5). Crayfish are shown in the release chamber, as they were positioned prior to a trial. The open and closed positions of the chamber in the end wall configuration are shown. End line and outer limit of observation zones that determined wall following are marked with dotted rectangles.

View larger version (148K): [in a new window]   Fig. 2. Photographs of sections of three of the textured walls, board (PVC weather board, no.1), sandpaper (40 grit, no. 2), and bubble wrap (no. 4).

View larger version (33K): [in a new window]   Fig. 3. Tracking of crayfish through the different environments. (A) Coordinates of the rostrum were tracked and angles measured between successive points. Three examples are shown for a crayfish that started parallel to the wall (0°), then moved away from the wall (negative angles up to -90°) and then moved back toward the wall (positive angles up to 90°). A reference coordinate was also logged (white circle on wall). An example of the calculation of angles is shown below. (B) A crayfish in the laneway of the texture experiment with its flagella spread to contact the wall on each side. Four points were tracked - rostrum, tailfan edge, left and right antennae - as indicated by solid circles. Apparatus reference coordinates of the centre line start point and one of the walls were also taken (white circles). Angles indicated for the antennae movement:x, angle at which each antenna was held with respect to the body axis, andx, angle between the antennae.

View larger version (22K): [in a new window]   Fig. 4. Heading angles (means + s.e.m.) of crayfish that did and did not follow walls for the middle and end releases along the straight wall, and the corner treatment. Crayfish that followed walls had larger heading angles and these were away from the wall (negative). Angles of zero degrees indicate heading parallel to the wall. Number of animals out of 10 that were followers is given in each bar. Asterisks indicate groups of crayfish that did not follow walls (Fisher's exact P<0.05; see text).

View larger version (13K): [in a new window]   Fig. 5. Movement of crayfish through each of the four wall configurations. Wall configurations are shown by grey lines. The tracked path of one of the 10 animals that started from the crayfish icon is shown as a black line. Dots along the path represent subsequent 1 s measurements (2 s in the square configuration). White squares indicate apparatus reference points.

View larger version (21K): [in a new window]   Fig. 6. Percentage of time spent in the two laneway regions (mean + s.e.m.), centre and sides. The time spent in a region was different, and this difference varied depending on the texture of the walls. Asterisks indicate significant differences between regions within each texture (see Table 2 and main text for P values). Crayfish spent about 50% of time in each region for the smooth (sm) and sandpaper smooth (ss) textures, more time in the sides in the bubble wrap (b) and board (bd) textures, and more time in the centre with the sandpaper walls (sr).

View larger version (12K): [in a new window]   Fig. 7. Summary of angle measurements to indicate crayfish body and antenna position in the laneway. Heading and maximum heading angles are shown at the posterior end of the crayfish, 5±1° and 14±4° respectively (mean ± s.e.m.). Antennae were spread 48±3° either side of the body axis and with a mean angle of 95±7° between the two antennae.