QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

First published online January 8, 2007
Journal of Experimental Biology 210, 198-207 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.02657

This Article Summary Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Related articles in JEB Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Wittlinger, M. Articles by Wolf, H. Search for Related Content PubMed PubMed Citation Articles by Wittlinger, M. Articles by Wolf, H.

The desert ant odometer: a stride integrator that accounts for stride length and walking speed

Matthias Wittlinger^1,*, Rüdiger Wehner² and Harald Wolf¹

¹ Institute of Neurobiology, University of Ulm, Albert-Einstein-Allee 11, D-89069 Ulm, Germany
² Institute of Zoology, University of Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland

View larger version (5K): [in this window] [in a new window]   Fig. 1. Experimental situation. Schematic diagram of channel layout; training channel, top; test channel, bottom (broken lines indicate extended length of test channel to 24 m). The search behaviour exhibited by Cataglyphis foragers after having run off their home vector is illustrated schematically below the test channel. Not drawn to scale. N, north.

View larger version (8K): [in this window] [in a new window]   Fig. 2. Manipulation of leg length. The right hind leg of a Cataglyphis fortis worker is shown from the anterior [adapted from fig. 1 in Wehner (Wehner, 1983)], and the manipulations performed in the present study are indicated: stumps II and I, the removal of the distal part of the leg from the mid tibia, and removal of the tarsi, respectively; a normal leg; and stilts, the addition of pig bristles to lengthen the leg.

View larger version (64K): [in this window] [in a new window]   Fig. 3. Tripod gait of a Cataglyphis individual before (normal) and after leg shortening (stumps II). The six complete strides captured by the high-speed video are shown, and indicated as the tripods performed by the animal in its normal tripod gate. Tripods formed by the left front and hind (L1, L3) and right middle (R2) legs are drawn in blue; those formed by the right front and hind (R1, R3) and left middle (L2) legs are drawn in red. Stride length (s2) was determined as the distance between two successive middle leg footfalls. (A) Untreated normal situation, showing the typical tripod gait (s2=13.3 mm; v=0.28 m s-1). (B) After leg shortening the ant still shows the typical tripod gait but with obviously decreased stride length (s2=10.5 mm; v=0.27 m s-1). Single video frames of the ant, taken during the 1st and 6th captured strides, are pasted into the tripod analysis.

View larger version (32K): [in this window] [in a new window]   Fig. 4. Homing distances of experimental ants. The top panels show search density plots (abscissae, homing distance; ordinates, cumulated relative search densities between the first and sixth turning points; see Materials and methods), the bottom panels show box-and-whisker plots (medians of the initial six turning points; compare Fig. 1,bottom), derived from the same data sets (N=25 ants for each experimental situation). (A) The ants were tested immediately after the lengths of their legs had been modified at the feeding site, that is, leg lengths were normal during the outbound journey but manipulated during the homebound run (Test 1). (B) The ants were tested after re-emerging from the nest after previous manipulation. In this situation leg lengths were equal, though manipulated, during outbound and homebound runs (Test 2). The hatched box plots in the lower panel of A illustrate the search centres as predicted from the high-speed video analyses of stride lengths in normal and manipulated animals; for details see text. Colour code: red, stilts; blue, normal; yellow, stumps I; green, stumps II.

View larger version (8K): [in this window] [in a new window]   Fig. 5. Widths of search density distributions change with altered leg length. The half widths (width of graph at half-maximum height) of the search density distributions in Fig. 4 were determined. They are shown for the different experimental situations, Test 1, top, Test 2, bottom. Colour code: red, stilts; blue, normal; yellow, stumps I; green, stumps II.

View larger version (14K): [in this window] [in a new window]   Fig. 6. Relationship between (relative) stride length and stride frequency in normal ants and after manipulation of leg length. Stride length was normalised with regard to body size (alitrunk length, see Materials and methods), and is shown on the ordinate; the abscissa gives stride frequency. Each data point represents one individual. Best fit regression lines are indicated; the respective equations are, from top to bottom: stilts, stride length=0.124xstride frequency+2.14; normal, stride length=0.084xstride frequency+1.89; stumps I, stride length=0.061xstride frequency+1.788; stumps II, stride length=0.057xstride frequency+1.42 (stride frequency = Hz). Colour code: red, stilts; blue, normal; yellow, stumps I; green, stumps II.

View larger version (24K): [in this window] [in a new window]   Fig. 7. The relationship between walking speed and (A) stride frequency, (B) (relative) stride length. The different experimental situations are colour-coded as in the previous figures: red, stilts; blue, normal; yellow, stumps I; green, stumps II. Linear regression lines are indicated. The regression lines for the normal ants: stride frequency=0.054xwalking speed+7.72 (R2=0.87) in A; stride length=0.018xwalking speed+6.80 (R2=0.81) in B (stride frequency = Hz, stride length = mm and walking speed = mm s-1).