What is UVB?
UVB, or Ultraviolet, is a type of radiation.
There are three types of Ultraviolet.
Ultraviolet A (UVA) radiation has the longest wavelength of the three and is associated with ageing and long-term skin damage. This type of UV is used in tanning beds as it stimulates melanin production. It also contributes to vitamin D synthesis.
Ultraviolet B (UVB) radiation has a medium wavelength and is more energetic than UVA. It is primarily responsible for skin damage and sunburns and is the wavelength that reacts with 7-DHC to produce pre-vitamin D.
Ultraviolet C (UVC) radiation has the shortest wavelength and is mostly absorbed by the earth’s ozone layer. UVC is very energetic and is highly effective at damaging DNA and killing microorganisms. UVC is often used in sterilisation.
UVB is measured using Ferguson Zones.
Ferguson Zones were originally created by Dr Thomas Ferguson, a dermatologist, to help people with different skin types and colours to understand their risk of sunburn.
Different species of reptile are assigned different Ferguson Zones, or Ultraviolet Indexes (UVIs) as a guide to what amount of UVB they need to be provided with.
Sun-worshipping species like Bearded Dragons and Uromastyx require high levels of UVB, putting them in Ferguson Zone / UVI 4 - 6.
Crepuscular species like Leopard Geckos require a UVI of 1 - 2.
Devices that can accurately measure UVI are expensive and hard to find. Currently, the Solarmeter 6.5r and Solarmeter 6.5 are the only devices on the market that are considered reputable. At £250, they are more expensive than most reptile keepers can justify spending, and so most must rely on lighting guides or experienced keepers to assist with their setups.
UV output on individual bulbs will vary depending on the brand, and how the bulb is installed in the enclosure. It is important to seek the advice of experienced keepers when installing your bulb, as mesh type, distance from the basking platform, and the brand of bulb will vary it’s output.
UVB Bulb outputs degrade as they age, with most lasting 6 - 12 months. It is important to adhere to the manufacturer guidelines and replace bulbs as recommended.
What does UVB do?
UVB is crucial for the natural production of Vitamin D3, which regulates calcium and phosphate metabolism.
So, how does it go from radiation to vitamin?
7-dehydrocholesterol or 7-DHC is a compound that is synthesised in the liver from cholesterol. It is then transported in the blood to the skin.
7-DHC absorbs UVB radiation and undergoes a process called photosiomerisation. This process converts 7-DHC to previtamin D3.
The body then uses heat to further process the previtamin D3. In humans and other endothermic (warm-blooded) animals, body heat is used for this. However, in ectothermic (cold-blooded) reptiles, an external heat source is required for this process.
The previtamin D3 then travels through the bloodstream to the liver and kidneys, where it undergoes additional metabolic processes to become active Vitamin D3.
Vitamin D3 is crucial for regulating calcium and phosphate metabolism in the body, all of which is essential for bone health and other physiological functions.
Although UVB is crucial for the above process, overexposure can be dangerous and it is important to ensure you are using appropriate equipment and that it is set up safely. Failing to do so will result in the over or under absorption, which can have dire consequences.
Setting up UVB for Leopard Geckos
UVB should be set up with a clear gradient, allowing the animal to regulate how much they take in.
The UVB fixture should take up 1/3 of the enclosure, and sits on the warm side of the enclosure allowing the temperature gradient and the UV gradient to coincide.
Please note this diagram is not to scale, and should not be the sole reference point for setting up UVB in an enclosure.
Should albino Leopard Geckos have access to UVB?
Yes, albino geckos utilise UVB the same as non-albino animals. They can take longer to adapt to the light, and may need additional clutter in their enclosures, but they will use it.
I never see my gecko basking, is something wrong?
Leopard Geckos are crepuscular, and so don’t often actively bask. Instead, they will cryptic bask. This involves them poking a limb, tail, or nose into the light which will enable them to absorb UVB and infrared while remaining hidden. Being prey animals, they often find this preferable to being in the open.
What sort of UV bulb should I use?
It is easier to note which bulbs are not suitable. Coil or compact UVB bulbs will give off unstable levels of UV and can easily cause burns. Any bulb that offers both LED and UVB is unsafe - the technology for these is on the way, but isn’t there yet. For Leopard Geckos, UV bulbs should cover 33 - 50% of the enclosure, creating a smooth gradient of light. The specific bulb needed varies between enclosures and setups.
Do I need to use overhead heating with UVB?
It is best to use overhead heating for Leopard Geckos, as they provide a better ratio of infrared and therefore encourage natural behaviours such as basking. Heat Mats are inefficient and not suitable for Leopard Geckos.