Zoo Med NatureSun User Manual

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Rethinking Reptile

Reptile and amphibian lighting from a natural-history perspective.

by Shane Bagnall

www.reptilechannel.com | 3

While some geckos

to

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are diurnal, like this
Madagascar giant day
gecko, many nocturnal
geckos become active at
dusk and receive low levels
of UVB before the sun sets.

n the early 1940s, our knowledge of the
effects of light on reptiles and amphibians
was very limited. It wasn’t until 1944
that we learned of the amazing ability of
reptiles to maintain relatively stable body
temperatures through thermoregulation.

This was the result of a groundbreaking
study by herpetologists Raymond Cowles and
Charles Bogert, who coined the terms “ectotherm”
and “endotherm.” Their landmark study inspired
numerous research projects on the effects of light
and heat on reptiles.
Since then, our knowledge of reptile
lighting has increased tremendously. We now
know that many reptiles and amphibians can see
things illuminated by ultraviolet-A, and that they
can make vitamin D in their skin upon exposure

to ultraviolet-B. When housed in captivity

without access to UVB, many reptiles

developed a form of metabolic

bone disease (MBD) that

results in soft, deformed

Courtesy Kirby Spencer / Zoo Med Laboratories

2 | Reptiles

Rep

bones and is often fatal
if not corrected by UVB
exposure. With this
knowledge came the
introduction of the
fi rst commercially
available UVB
lamp for reptiles
in 1993, which
allowed people
to successfully
maintain and
breed a variety of
reptile species in
captivity. Although
preventing the onset
of disease is good
motivation to provide
adequate lighting for
captive reptiles, many
keepers are going to
the next level in an effort
to accurately recreate truly
naturalistic habitats, even with
respect to lighting.
Humans see the world differently
than reptiles and amphibians. Many reptiles and
amphibians have the remarkable ability to see
things illuminated by UV wavelengths. Also, some
lizards and amphibians have a third eye on the top
of their head known as the parietal eye. This eye
cannot see the full complement of colors that the
other two eyes see, but it can sense light and is
associated with photoperiod regulation (circadian
rhythms), reproductive behavior, basking behavior
and thermoregulation. The parietal eye may also
be sensitive to UV wavelengths (Jenison, 1980).
These differences in how reptiles and humans see
have caused persistent confusion on what defi nes
full-spectrum lighting and UV lighting.

Full-Spectrum and UV Lighting

The term “light” is typically associated
with vision, and because people are the ones
doing the research, we have identifi ed the
visual portion of the electromagnetic spectrum
according to the colors that we are able to see.
Full-spectrum lighting for reptiles should have
emissions in the human visible wavelengths (red

Panther chameleons have been the

subject of much UVB research over

the years. This hatchling was bred at

Zoo Med and receives UVB from an

energy-effi cient, compact fl uorescent

UVB lamp.

Courtesy Kirby Spencer / Zoo Med Laboratories

Photoherpetology

Many think of the word “photo”

eferring to a picture, but

as r
the original meaning of the
word is “light.” “Photograph”
literally means “drawing with
light.” The study of the effects
of light, or photons, on living
things is called photobiology.
Herpetology is defi ned as
the study of reptiles and
amphibians. By combining
these two terms, I propose a
new word to give identity to the
growing fi eld of the study of
reptile and amphibian lighting:
photoherpetology.

Reptiles | 3

tiles | 3

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Rep

This electromagnetic
spectrum shows the
difference between the
vision of humans and
the vision of reptiles and
amphibians.

Courtesy Shane Bagnall

through violet), in
addition to emissions
in the UVA region of
the electromagnetic
spectrum. It is
important to note
that a full-spectrum
reptile lamp may not
produce UVB, unless
the manufacturer
specifi cally states so on
the package.
The shorter
wavelengths adjacent
to the human visible
wavelengths of the
electromagnetic

spectrum are
appropriately called ultraviolet. These wavelengths
are broken into three categories: UVA, UVB
and UVC. As mentioned, many reptiles and
amphibians can see things illuminated by UVA
light, and thus UVA makes up a portion of their
visible spectrum. UVB wavelengths are shorter
than UVA wavelengths and may or may not be
visible. Even though lamps are used to produce
UVB, the term “UVB light” is a bit of a misnomer,
because animals may not have the ability to see
things illuminated by UVB wavelengths. UVB
is associated with synthesis of vitamin D in the
skin, in addition to playing a role in the immune
system of animals. There is evidence that reptiles
can sense UVB and will adjust their exposure
based on the amount of vitamin D in their blood.
UVC and shortwave UVB wavelengths below
290 nanometers do not penetrate the earth’s
atmosphere and are harmful to animals.

4 | Reptiles

UVB, Vitamin D and Calcium

The process of vitamin D synthesis in
the skin of animals upon exposure to UVB is
fascinating. Cholesterols in the skin are converted
to a molecule known as previtamin D3 when the
skin is exposed to UVB radiation. Upon exposure
to heat, previtamin D3 undergoes a change and
is converted to vitamin D3, which transforms in
the liver and kidneys to the active form of vitamin
D3. There are other molecules involved, and the
process is regulated so that excess UVB exposure
will not lead to an overdose of vitamin D, which is

tiles