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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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Head angles measured relative to the threat.An overhead view of the sagittal plane of the head of a chameleon (C) when perched vertically on a pole (P), in relation to the threat (T); α – the angle in relation to the threat, β – the angle in relation to both threat and pole.
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pone-0037875-g002: Head angles measured relative to the threat.An overhead view of the sagittal plane of the head of a chameleon (C) when perched vertically on a pole (P), in relation to the threat (T); α – the angle in relation to the threat, β – the angle in relation to both threat and pole.

Mentions: To determine whether the chameleon’s correction of position is a vestibular-driven compensatory response, we performed two control experiments: (a) the pole was rotated without a visual threat and (b) the threat was rotated, while the pole was kept stationary. In control experiment (a), the vertical pole was placed inside an opaque-white plastic sphere, 35 cm in diameter. The chameleons (n  = 4), when perched on the pole, could view only the pole and its base but no obvious threats. In each test, the pole was rotated in succession 10 times clockwise and 10 times counter-clockwise at an angular velocity of ∼15°/s [see Video S1]. In control experiment (b), a threat stimulus (a head figurine 5×10 cm) was moved 50 cm from the pole in an arc of ca. 80° [see Video S2]. The chameleons (n  = 2) were tested for their response to the threat when perched on the pole and level with the threat. Ten tests were performed at each of three angular velocities (15°, 35° and 70°/s). For each angular velocity, three arbitrary tests were chosen for analysis. Two angles were analyzed: angle α–formed by the sagittal plane of the head relative to the threat, and angle β–formed by the sagittal plane of the head relative to the threat, through the pole. Angle β determined the chameleon’s position behind the pole relative to the threat and may be regarded as a measure of the level of visual concealment (Fig. 2).


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

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

Head angles measured relative to the threat.An overhead view of the sagittal plane of the head of a chameleon (C) when perched vertically on a pole (P), in relation to the threat (T); α – the angle in relation to the threat, β – the angle in relation to both threat and pole.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0037875-g002: Head angles measured relative to the threat.An overhead view of the sagittal plane of the head of a chameleon (C) when perched vertically on a pole (P), in relation to the threat (T); α – the angle in relation to the threat, β – the angle in relation to both threat and pole.
Mentions: To determine whether the chameleon’s correction of position is a vestibular-driven compensatory response, we performed two control experiments: (a) the pole was rotated without a visual threat and (b) the threat was rotated, while the pole was kept stationary. In control experiment (a), the vertical pole was placed inside an opaque-white plastic sphere, 35 cm in diameter. The chameleons (n  = 4), when perched on the pole, could view only the pole and its base but no obvious threats. In each test, the pole was rotated in succession 10 times clockwise and 10 times counter-clockwise at an angular velocity of ∼15°/s [see Video S1]. In control experiment (b), a threat stimulus (a head figurine 5×10 cm) was moved 50 cm from the pole in an arc of ca. 80° [see Video S2]. The chameleons (n  = 2) were tested for their response to the threat when perched on the pole and level with the threat. Ten tests were performed at each of three angular velocities (15°, 35° and 70°/s). For each angular velocity, three arbitrary tests were chosen for analysis. Two angles were analyzed: angle α–formed by the sagittal plane of the head relative to the threat, and angle β–formed by the sagittal plane of the head relative to the threat, through the pole. Angle β determined the chameleon’s position behind the pole relative to the threat and may be regarded as a measure of the level of visual concealment (Fig. 2).

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