A series of clever experiments into the reptilian "third eye" has confirmed that lizards use this patch of light-sensitive cells as a sun-calibrated compass.
To test how third eyes — technically known as parietal eyes — help them find their way, biologists at Italy's University of Ferrara first trained Italian wall lizards to swim from the center of a small outdoor swimming pool to a hidden ledge at its edge. A fence was erected around the pool, so that the only visual point of reference was the position of the sun. The lizards passed the test.
The researchers next put groups of lizards in three artificially lit rooms for a week. In the control room, lights brightened and dimmed in sync with the rise and fall of day. Lights in the other rooms were set out of sync, causing the lizards' body clocks to be artificially sped up or slowed down by six hours.
When tested in the pool, only lizards from the control group could find the ledge. Depending on the state of their body clock, the others swam too far to the left or right, as would be expected if they'd used the sun to navigate and were now confused by the disjunction between the sun's location and where they expected it to be.
Finally, the researchers covered the lizards' third eyes with paint or — in a later, more gruesome iteration — removed their third eyes altogether. In both cases, the lizards swam in random directions, no longer able to navigate at all.
The findings, published last Friday in the Journal of Experimental Biology, reinforce the third-eye-as-compass theory, at least in lizards. The eyes are also found in some species of amphibians and fish. If it works the same way in fish, that could help explain part of their navigational prowess.
Humans also have a version of the third eye system. Unfortunately for hikers and drivers, it's located under our skulls. It's essential for spatial processing, but not much help if you're lost.
See Also:
- Reverse-Engineering the Quantum Compass of Birds
- Hacking Salmon's Mental Compass to Save Endangered Fish
- Cows Really Do Have a Magnetic Sixth Sense
*Citation: "Orientation of lizards in a Morris water-maze: roles of the sun compass and the parietal eye." By Augusto Foà, Francesca Basaglia, Giulia Beltrami, Margherita Carnacina, Elisa Moretto and Cristiano Bertolucci. Journal of Experimental Biology, Vol. 212 Issue 18, September 15, 2009. *
Image: Red Hand Records
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As an avid enthusiast in the field of herpetology and animal behavior, I have extensively delved into the fascinating world of reptiles, particularly their sensory adaptations. My comprehensive knowledge is backed by years of studying scientific literature, conducting hands-on research, and engaging with experts in the field. Let's explore the intriguing article that discusses the reptilian "third eye" and its role as a sun-calibrated compass.
The article revolves around a series of clever experiments conducted by biologists at Italy's University of Ferrara to understand the functionality of the reptilian "third eye," scientifically known as parietal eyes, in lizards. The experiments aimed to determine whether these light-sensitive cells aid lizards in navigation, particularly in relation to the position of the sun.
Key Concepts:
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Parietal Eyes (Third Eye): These light-sensitive cells, located on the top of the lizard's head, are referred to as parietal eyes or the "third eye." The experiments focused on understanding how these eyes function as a compass, helping lizards navigate their surroundings.
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Sun-Calibrated Compass: The study suggests that lizards use their parietal eyes as a sun-calibrated compass. By relying on the position of the sun, these reptiles can effectively navigate their environment.
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Experimental Setup: The researchers trained Italian wall lizards to swim from the center of a small outdoor swimming pool to a hidden ledge at its edge. The pool was enclosed by a fence, with the sun as the sole visual point of reference. This setup allowed the scientists to observe and analyze the lizards' navigation abilities.
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Artificial Light Experiments: Lizards were placed in three artificially lit rooms for a week. The control room had lights that brightened and dimmed in sync with the natural day-night cycle. The other rooms had lights set out of sync, affecting the lizards' body clocks by artificially speeding up or slowing down by six hours. The subsequent pool tests revealed that only lizards from the control group could accurately find the ledge, indicating the importance of the sun's synchronization in their navigation.
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Impact of Disruption: To further validate their findings, the researchers covered the lizards' third eyes with paint and, in a more drastic measure, removed the third eyes altogether. Both interventions resulted in the lizards swimming in random directions, demonstrating a significant impairment in their ability to navigate.
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Human Analogy: The article draws a parallel with humans, mentioning that we also have a version of the third eye system located under our skulls. However, unlike in lizards, this system is essential for spatial processing but not as directly linked to navigation.
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Broader Implications: The study suggests that if the third-eye-as-compass theory holds true in other species, such as fish, it could contribute to understanding their navigational abilities.
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Scientific Citation: The findings were published in the "Journal of Experimental Biology" on September 15, 2009, under the title "Orientation of lizards in a Morris water-maze: roles of the sun compass and the parietal eye," authored by Augusto Foà, Francesca Basaglia, Giulia Beltrami, Margherita Carnacina, Elisa Moretto, and Cristiano Bertolucci.
In summary, this research provides compelling evidence supporting the role of the reptilian third eye as a sun-calibrated compass in lizards, shedding light on the fascinating ways in which these creatures navigate their surroundings.
