The Bearded Dragons Third Eye: Anatomy & Influence on Care

The bearded dragons third eye, known as their parietal eye, is one of the most intriguing features of these reptiles. The parietal eye is a very important part of a bearded dragon’s anatomy and plays a significant role in their behavior and care. In this article, we delve into the details of the bearded dragons third eye, exploring its location, function, and impact on husbandry practices.

bearded dragons third eye also known as parietal eye

What is a bearded dragons third eye?

Like our regular eyes, the bearded dragons third eye is a photoreceptive organ. It helps these reptiles gauge the intensity and duration of daylight. This eye is not able to form detailed images like their main eyes but serves a different and significant purpose. It is a part of the pineal gland system and is crucial for sensing changes in light and temperature.

The parietal eye is connected to the pineal gland. Together the parietal eye and the pineal gland are known as the pineal complex which are both photosensitive (Tosini, 1997). The parietal eye has a lens, cornea, and retina (Tosini, 1997).

Where is a Bearded Dragons Third Eye and What Does it Look Like?

The bearded dragons third eye (parietal eye) is situated on the top of their head.

This small, round pigmented dot is covered by a translucent scale, often greyish in color. This placement is strategic, allowing the dragon to sense overhead threats and changes in its environment.

How Does the Third Eye Work?

The third eye is connected to the pineal gland, a part of the brain that produces hormones like melatonin. The third eye sends signals to the pineal gland by communicating with the optic centre of the brain (Sawnee Animal Clinic).

This eye is sensitive to light and shadow changes above the bearded dragon. Unlike the lateral eyes, the third eye doesn’t form distinct images but detects variations in light intensity and UV radiation.

bearded dragons parietal eye, also know as third eye

What Does The Third Eye Do?

The primary function of the third eye is to help regulate the bearded dragon’s circadian rhythms and hormonal balance. It plays a crucial role in sensing predators from above, as sudden changes in light and shadow can indicate the presence of a bird or other threat. Additionally, it aids in thermoregulation by sensing the intensity of sunlight, which is vital for these cold-blooded animals.

The role of the pineal complex varies between reptile classes (Tosini, 1997). From as far back as 1958 in experiments by Stebbins and Eakin the parietal eye has been shown to assist diurnal lizards in regulating the amount of sunlight they need and preventing excessive metabolic activity which shortens life. The parietal eye detects light and dark measuring the photoperiod of light (Sawnee Animal Clinic).

The pineal gland (connected to the parietal eye) produces different hormones depending on the time of day including melatonin (Divers and Stahl, 2018) which helps in the sleep and wake cycle. The pineal complex sets the internal clock, detecting the season and even time of day which regulates the production of hormones.

The bearded dragons pineal eye (third eye) is pivotal in initiating brumation, a hibernation-like state. It senses changes in light and temperature associated with seasonal transitions. As days shorten and temperatures drop, the pineal eye detects these changes, influencing the dragon’s circadian rhythms. This leads to increased melatonin production by the pineal gland, inducing dormancy behaviors. The bearded dragon responds by reducing its metabolism, food intake, and activity levels, preparing for brumation. This light-sensitive organ thus plays a crucial role in aligning the bearded dragon’s biological processes with environmental cues, ensuring their well-being and survival through seasonal changes.

Bearded dragons need to detect light and dark for thermoregulation and production of hormones. The parietal eye plays a role in metabolism. Melatonin is the most important secretory product of the pineal complex and influences thermoregulation (Tosini, 1997).

In some lizards, when the parietal eye was removed, the lizards selected higher temperatures and more exposure to sunlight (Firth et al, 1988) This resulted in higher metabolic activity than that of lizards that still had their parietal eye. The higher metabolic activity shortens life (Stebbins and Eakin,1958).

Research by Tosini and Menaker (1998) on iguana’s found that when the parietal eye was removed there was a slight effect on thermoregulation. However, when the pineal gland was removed, the iguanas could not thermoregulate at all.

In addition, the third eye has a role to play in appetite; level of energy and early warning of predators overhead. The third eye could be the reason why a bearded dragon can become scared, terrified even, about being outside when it is used to being indoors. The change in the quality and brightness in light from artificial light to sunlight may cause the scared reaction of a bearded dragon.

In the Italian wall lizards, it was found through the third eye was required for navigation (Foa et al, 2009). Without it, the lizards could not navigate through a maze.

Third eye detects overhead movement, bearded dragon frightened from overhead fan
Aries is frightened by the overhead fan. Mallorys bearded dragon.

What Happened When the Parietal Eye was Surgically Removed From Some Lizards?

Stebbins and Eakin (1958) conducted experiments on the parietal eye and although this study is aged, it still holds valuable information. Using four species of western North American lizards the third eye was either surgically removed (parietalectomy) or covered with aluminium foil. The results included:

Much slower to find refuge from danger: The parietalectomized lizards showed a diminished fright response, moving less distance and emerging quicker from cover than those with an intact parietal eye. They were less inclined to retreat upon the approach of an observer, which can be interpreted as a reduced tendency to seek refuge, potentially including from predators.

Got out of bed earlier in the morning: Post-parietalectomy, all four lizard species exhibited increased exposure to sunlight. This was evident in both field and laboratory settings, showing prolonged ground surface activity and preference for higher-intensity illumination.

Removing the parietal eye did not affect body temperature: The parietalectomized lizards extended their time spent at ‘normal activity’ thermal levels. However, despite greater exposure to high temperatures, their body temperature was similar to normal lizards. Increased activity was noted, but without a corresponding increase in body temperature.

Thyroid gland enlarged: Parietalectomized lizards had an enlarged thyroid gland with a loss of colloid in parietalectomized lizards, suggesting a link to the behavioral changes.

Parietalectomized lizards were able to move more: Parietalectomized lizards showed three times greater displacement from their home ranges than sham-operated ones and were less inclined to retreat upon the approach of an observer. This suggests a significant change in their normal behavioral patterns due to the removal of the parietal eye.

The parietal eye impacts time in the sun and on the ground: The parietal eye is involved in regulating exposure to sunlight and the amount of time lizards spend on the ground’s surface. The increased exposure to sunlight following the removal or impairment of the parietal eye indicates that the eye functions in inhibiting activity levels dependent on solar radiation.

Without food parietalectomized lizards die: Parietalectomized lizards were found to be at a disadvantage in both behavior and vitality. When deprived of food, all but one of the parietalectomized lizards died before the control group. This reduced vitality, however, was not due to differences in surgery but rather seemed to be affected by the destruction of the parietal eye and possibly related to:

  1. increased exposure to higher temperatures,
  2. greater activity​ possibly due to increased metabolism, and
  3. faster exhaustion of energy reserves.

The parietal eye is not connected to the eyes and brain: Microsections of the parietal eye showed no nerve connection between the eye and the brain. The retina appears to be secretory, with activity likely varying with solar radiation intensity.

The study concludes that the parietal eye in these diurnal lizards helps regulate sunlight exposure. It seems to play a role in inhibiting activity after certain exposure periods, potentially to prevent metabolic excesses and conserve energy reserves. Thus, the parietal eye may significantly influence the lizards’ activity intensity and duration, impacting their overall life span.

How the Bearded Dragons Third Eye Impacts Husbandry Practices

The bearded dragons third eye is an important consideration in husbandry practices. Here are 5 considerations in husbandry practices:

1. Never approaching a bearded dragon from overhead

Use caution approaching from overhead as the bearded dragons third eye is sensitive to changes in light which shadows create. The shadow of a bird flying overhead may not be distinguishable from your hand moving over its head. Approach in a non-threatening manner, preferably from the side rather than directly from above, to reduce stress and avoid startling them.

2. Do not provide bearded dragons with light at night

The photosensitive nature of the eye is why bearded dragons need dark at night. The pineal eye can detect light including ultrared and ultraviolet light. This is why lights, whether white or red, should not be used at night, they disturb sleep. Conversely it is also why bright white light should be used during the day. The light directly impacts the biological clock. More on bearded dragons surprising sleep habits here.

3. Moving between sunlight and artificial light

The bearded dragons third eye is quite sensative and can become agitated when moving between sunlight and artificial light. It is very likely that the bright sunlight has triggered something through the third eye. The only action is to remain aware of likely changes in behaviour that could occur.

4. Bright tank light is critical to biological functions

As the bearded dragons third eye is photosensitive and is critical to biological functions, it is important to provide bright day light. Ideally sunlight during the day is best however where that is not possible, bright cage lights are needed.

5. Automate the lighting cycles with timers

Along with bright light, lighting cycles are needed to ensure that hormone production and other biological functions of the bearded dragons third eye are working correctly. Automating the lighting cycles will ensure consistency similar to that of the natural environment. For setting up lighting and cycles in the post simplifying lighting.

Bearded Dragons Third Eye Impacts Handling

When it comes to handling your bearded dragon around its head where the pineal gland and third eye are located, be gentle and understanding of their comfort levels. The third eye, located on the top of their head is a crucial part of their sensory system.

It’s okay to lightly stroke the head but avoid applying pressure directly on the third eye. This area is sensitive and pressing on it could be uncomfortable or even harmful to them. Observing their reactions and respecting their boundaries is key to a happy and healthy petting experience.

Bearded Dragons Third Eye Conclusion

The bearded dragons third eye is like a little secret superpower that plays a big part in keeping it happy and healthy. This special sensor on top of their heads helps them keep track of day and night, making sure they stay warm and cozy and get the right hormones at the right times. It’s kind of like their built-in biological clock.

The bearded dragons third eye is an important reason for providing darkness at night and bright sunlight during the day. Their third eye is sensitive and can pick up on different kinds of light, which might mess with their sleep if they’re exposed to light at night.

Have you ever noticed your bearded dragon acting a bit jumpy or different when you take them outside? This could be because their third eye is reacting to the bright, natural sunlight, or a shadow overhead which could signal predator coming for them. Getting some sun is great for them and can help prevent health issues. Just be sensitive to their needs for protection by providing them shelter to hide in if they feel the need.

References

  1. Firth, B., Mauldin, R., & Ralph, C. (1988) The Role of the Pineal Complex in Behavioral Thermoregulation in the Collared Lizard Crotaphytus collaris under Seminatural Conditions. Physiological Zoology, 61(2), 176-185
  2. Foà, A., Basaglia, F., Beltrami, G., Carnacina, M., Moretto, M., and Bertolucci, C. (2009) Orientation of lizards in a Morris water-maze: roles of the sun compass and the parietal eye. Journal of Experimental Biology. 212: 2918-2924
  3. Stebbins, R. C., and Eakin, R. M. (1958) The role of the “third eye” in reptilian behavior. American Museum Novitates 1870:1-40
  4. Tosini, G. (1997) The pineal complex of reptiles: Physiological and behavioral roles. Ethology Ecology & Evolution – Ethology Ecology and Evolution. 9(4)
  5. Tosini, G., & Menaker, M. (1998). Multioscillatory Circadian Organization in a Vertebrate,Iguana iguanaThe Journal of Neuroscience18(3), 1105–1114.
  6. Sawnee Animal Clinic. Cumming. Georgia, USA