Limits...
Visually guided avoidance in the chameleon (Chamaeleo chameleon): response patterns and lateralization.

Lustig A, Ketter-Katz H, Katzir G - PLoS ONE (2012)

Bottom Line: We found two equal-sized sub-groups, each displaying lateralization of motor responses to a given direction of stimulus approach.Such an anti-symmetrical distribution of lateralization in a population may be indicative of situations in which organisms are regularly exposed to crucial stimuli from all spatial directions.This is because a bimodal distribution of responses to threat in a natural population will reduce the spatial advantage of predators.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurobiology and Ethology, University of Haifa, Haifa, Israel. Lustigavi@gmail.com

ABSTRACT
The common chameleon, Chamaeleo chameleon, is an arboreal lizard with highly independent, large-amplitude eye movements. In response to a moving threat, a chameleon on a perch responds with distinct avoidance movements that are expressed in its continuous positioning on the side of the perch distal to the threat. We analyzed body-exposure patterns during threat avoidance for evidence of lateralization, that is, asymmetry at the functional/behavioral levels. Chameleons were exposed to a threat approaching horizontally from the left or right, as they held onto a vertical pole that was either wider or narrower than the width of their head, providing, respectively, monocular or binocular viewing of the threat. We found two equal-sized sub-groups, each displaying lateralization of motor responses to a given direction of stimulus approach. Such an anti-symmetrical distribution of lateralization in a population may be indicative of situations in which organisms are regularly exposed to crucial stimuli from all spatial directions. This is because a bimodal distribution of responses to threat in a natural population will reduce the spatial advantage of predators.

Show MeSH

Related in: MedlinePlus

Experimental setup.(A) Oblique view. (B) Schematic overhead view. The experimenter, positioned behind the camera (a) acts as the threatening stimulus. Chameleon (x), vertical pole (b), incandescent bulbs (c), pole rotation cords (d), visual barrier (e), screen (f).
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC3369868&req=5

pone-0037875-g001: Experimental setup.(A) Oblique view. (B) Schematic overhead view. The experimenter, positioned behind the camera (a) acts as the threatening stimulus. Chameleon (x), vertical pole (b), incandescent bulbs (c), pole rotation cords (d), visual barrier (e), screen (f).

Mentions: Each tested chameleon was exposed to a threat that approached it from its left or right side in the following manner: the chameleon was placed on a vertical wooden pole that was between 3 mm and 14 mm in diameter. The pole could be rotated on its long axis either clockwise or counter-clockwise. Once the chameleon had settled, the pole was rotated in a 30° step (at ∼15°/s) in a given direction (Phase 1) and was then left stationary, allowing the chameleon to respond (Phase 2). The two phases were termed a “run” and each test comprised three consecutive runs. The experimenter acted as the “threat”, standing stationary ca. 120 cm from the pole so that the pole’s rotation resulted in relative movement of the chameleon toward the threat. Clockwise rotations resulted in a “left-approaching” threat toward the chameleon, while counter-clockwise rotations resulted in a “right-approaching” threat. The poles were either wide or narrow relative to the ventral width of the head of the tested chameleon. The wider pole allowed the chameleon to view the threat only monocularly at any given moment, whereas the narrower pole allowed the chameleon to view the threat both monocularly and binocularly. Each chameleon was tested once with a left-approaching threat and once with a right-approaching threat. Each test comprised three consecutive runs in the given direction. The tests were video-recorded with the camera positioned in front of the experimenter, 120 cm from the tested chameleon and at its level. From this position, the camera’s view was of the chameleon’s ventral side (Fig. 1).


Visually guided avoidance in the chameleon (Chamaeleo chameleon): response patterns and lateralization.

Lustig A, Ketter-Katz H, Katzir G - PLoS ONE (2012)

Experimental setup.(A) Oblique view. (B) Schematic overhead view. The experimenter, positioned behind the camera (a) acts as the threatening stimulus. Chameleon (x), vertical pole (b), incandescent bulbs (c), pole rotation cords (d), visual barrier (e), screen (f).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3369868&req=5

pone-0037875-g001: Experimental setup.(A) Oblique view. (B) Schematic overhead view. The experimenter, positioned behind the camera (a) acts as the threatening stimulus. Chameleon (x), vertical pole (b), incandescent bulbs (c), pole rotation cords (d), visual barrier (e), screen (f).
Mentions: Each tested chameleon was exposed to a threat that approached it from its left or right side in the following manner: the chameleon was placed on a vertical wooden pole that was between 3 mm and 14 mm in diameter. The pole could be rotated on its long axis either clockwise or counter-clockwise. Once the chameleon had settled, the pole was rotated in a 30° step (at ∼15°/s) in a given direction (Phase 1) and was then left stationary, allowing the chameleon to respond (Phase 2). The two phases were termed a “run” and each test comprised three consecutive runs. The experimenter acted as the “threat”, standing stationary ca. 120 cm from the pole so that the pole’s rotation resulted in relative movement of the chameleon toward the threat. Clockwise rotations resulted in a “left-approaching” threat toward the chameleon, while counter-clockwise rotations resulted in a “right-approaching” threat. The poles were either wide or narrow relative to the ventral width of the head of the tested chameleon. The wider pole allowed the chameleon to view the threat only monocularly at any given moment, whereas the narrower pole allowed the chameleon to view the threat both monocularly and binocularly. Each chameleon was tested once with a left-approaching threat and once with a right-approaching threat. Each test comprised three consecutive runs in the given direction. The tests were video-recorded with the camera positioned in front of the experimenter, 120 cm from the tested chameleon and at its level. From this position, the camera’s view was of the chameleon’s ventral side (Fig. 1).

Bottom Line: We found two equal-sized sub-groups, each displaying lateralization of motor responses to a given direction of stimulus approach.Such an anti-symmetrical distribution of lateralization in a population may be indicative of situations in which organisms are regularly exposed to crucial stimuli from all spatial directions.This is because a bimodal distribution of responses to threat in a natural population will reduce the spatial advantage of predators.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurobiology and Ethology, University of Haifa, Haifa, Israel. Lustigavi@gmail.com

ABSTRACT
The common chameleon, Chamaeleo chameleon, is an arboreal lizard with highly independent, large-amplitude eye movements. In response to a moving threat, a chameleon on a perch responds with distinct avoidance movements that are expressed in its continuous positioning on the side of the perch distal to the threat. We analyzed body-exposure patterns during threat avoidance for evidence of lateralization, that is, asymmetry at the functional/behavioral levels. Chameleons were exposed to a threat approaching horizontally from the left or right, as they held onto a vertical pole that was either wider or narrower than the width of their head, providing, respectively, monocular or binocular viewing of the threat. We found two equal-sized sub-groups, each displaying lateralization of motor responses to a given direction of stimulus approach. Such an anti-symmetrical distribution of lateralization in a population may be indicative of situations in which organisms are regularly exposed to crucial stimuli from all spatial directions. This is because a bimodal distribution of responses to threat in a natural population will reduce the spatial advantage of predators.

Show MeSH
Related in: MedlinePlus