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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.

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Related in: MedlinePlus

Ventral surface exposure used in the avoidance response analysis.A single frame from a sampled video sequence is depicted. (A) Unmodified image showing the ventral view of the chameleon holding onto a narrow pole, with its eyes protruding from both sides of the pole. (B) Body surface of the chameleon with the areas exposed on each side of the pole (hatched) used for the determination of respective surfaces. The caudal border of the area analyzed (broken horizontal line) is determined on the basis of 3×maximal head width, from the rostral end.
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pone-0037875-g003: Ventral surface exposure used in the avoidance response analysis.A single frame from a sampled video sequence is depicted. (A) Unmodified image showing the ventral view of the chameleon holding onto a narrow pole, with its eyes protruding from both sides of the pole. (B) Body surface of the chameleon with the areas exposed on each side of the pole (hatched) used for the determination of respective surfaces. The caudal border of the area analyzed (broken horizontal line) is determined on the basis of 3×maximal head width, from the rostral end.

Mentions: Video sequences were edited using Adobe Elements™ software. A specially written program (SIPL Lab, Technion, Israel) sampled the sequences at intervals of four frames (i.e., 160 ms) and provided the size of the surface of the chameleon’s body (in number of pixels) that was exposed on each side of the pole (Fig. 3). To overcome differences in the absolute body size of the tested chameleons and maintain uniformity of the data, a measure of the relative body surface exposed was employed for each chameleon. The maximal ventral width of the head (i.e., mandible width) was measured. Then, from the very rostral end of the head, a distance that was three times the maximal head width was measured caudally and a horizontal line was drawn, forming a caudal “borderline” (Fig. 3).


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

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

Ventral surface exposure used in the avoidance response analysis.A single frame from a sampled video sequence is depicted. (A) Unmodified image showing the ventral view of the chameleon holding onto a narrow pole, with its eyes protruding from both sides of the pole. (B) Body surface of the chameleon with the areas exposed on each side of the pole (hatched) used for the determination of respective surfaces. The caudal border of the area analyzed (broken horizontal line) is determined on the basis of 3×maximal head width, from the rostral end.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0037875-g003: Ventral surface exposure used in the avoidance response analysis.A single frame from a sampled video sequence is depicted. (A) Unmodified image showing the ventral view of the chameleon holding onto a narrow pole, with its eyes protruding from both sides of the pole. (B) Body surface of the chameleon with the areas exposed on each side of the pole (hatched) used for the determination of respective surfaces. The caudal border of the area analyzed (broken horizontal line) is determined on the basis of 3×maximal head width, from the rostral end.
Mentions: Video sequences were edited using Adobe Elements™ software. A specially written program (SIPL Lab, Technion, Israel) sampled the sequences at intervals of four frames (i.e., 160 ms) and provided the size of the surface of the chameleon’s body (in number of pixels) that was exposed on each side of the pole (Fig. 3). To overcome differences in the absolute body size of the tested chameleons and maintain uniformity of the data, a measure of the relative body surface exposed was employed for each chameleon. The maximal ventral width of the head (i.e., mandible width) was measured. Then, from the very rostral end of the head, a distance that was three times the maximal head width was measured caudally and a horizontal line was drawn, forming a caudal “borderline” (Fig. 3).

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