Tortoise Glossary Terms

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Glossary Terms:  U

Ultraviolet Light (UVL or UV):   

A type of light having a higher wavelength to that of visible light, just beyond the violet in the visible spectrum.  It is a light which we cannot see but it is the primary part of sunlight.  UV light has been found to have mutagenic properties.  UVL breaks down into three parts of the light spectrum UVA, UVB and UVC.  In the wild, many reptiles synthesise their own vitamin D3 from the UV component of sunlight.

Ultraviolet A:   

One of the three types of invisible light rays (together with ultraviolet B and ultraviolet C) given off by the sun.  It comprises over 99 per cent of that reaching the surface of the earth.  It enhances the harmful effects of UVB.  It affects chelonians behaviour and how food is visualised.

Ultraviolet B (UVB):   

Ultraviolet radiation comprising 1% of that reaching the surface of the earth.  Part of the light spectrum which helps to synthesis vitamin D in chelonians.  In tortoises, metabolic bone disease (MBD) is caused by a lack of UVB, as well as dietary factors.

Ultraviolet C (UVC):   

Ultraviolet radiation all of which is filtered out by the ozone layer and does not reach the surface of the earth; it is germicidal and is also used in ultraviolet phototherapy.

Ulcerative shell disease (USD):   

A wet or dry shell rot which requires urgent veterinary advice.


Represent the majority of nitrogenous waste in terrestrial chelonians.


The by product of the protein metabolism.

Uric acid:   

The excretion of waste material from arid habitat species (the toothpaste like content in the urine).


The clear or yellowish coloured liquid containing waste products that is excreted by the kidneys and discharged through the cloaca and which may contain urates.



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