Exotis ISSN 2398-2985

Reptiles

Lizard anatomy and physiology

Contributor(s): Vetstream Ltd, David Perpinan

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Integument

  • Lizard scales commonly overlap  and are created by a multi-layered epidermis that is shed at regular intervals during the life of the lizard. The Mexican beaded lizard has small bead-like scales that do not overlap .
  • The shedding of skin, known as ecdysis, occurs in multiple pieces in lizards , as opposed to snakes, in which the skin is usually shed in one piece:
    • Some lizard species eat the shed skin.
    • Factors that influence ecdysis are age, growth rate, temperature, humidity and nutrition.
    • Dysecdysis is commonly associated with low humidity and poor nutrition among other health abnormalities.
  • Reptilian epidermis does not have a respiratory function and contains very few glands.
  • The skin and scales are relatively impermeable in normal health. The mucous membranes (oral cavity, cloaca, conjunctiva) are quite permeable, however. This consideration is important when considering potential absorption of topical medications applied to these regions.
  • Some reptile vitamin supplements are marketed as sprays to be applied to the skin. These products, though not likely harmful, have little to no systemic physiologic value to reptiles.
  • Chamaeleo spp and Anolis spp have chromatophores in the skin that allow change in the reflectivity of visible light, resulting in color change. These changes are influenced by light, heat, social factors and reproductive status, but not by surrounding environmental color .
  • Foot and toe adaptations are diverse; integument specialization is quite notable in the fan-like adhesive disks of Gekkonidae. These species are capable of climbing glass and inverted smooth surfaces .
  • Large arboreal and terrestrial lizards usually possess sharp sturdy claws. Lizard claws are similar to those of birds; they have a pulp containing a blood vessel and nerve that is sensitive to short trimming.

Special cutaneous adaptations in lizards

  • There are some specialized skin glands and structures in lizards.  Most lizards kept in captivity have femoral or pericloacal pores, which are more developed in males .
  • Some geckos have precloacal pores.
  • Many lizards have large numbers of chromatophores in their skins; these are connected to neural networks, allowing them to alter the color they produce according to external stimuli and mood. This ability is seen in chameleons, and to a lesser extent, green iguanas and many other species .
  • Unlike snakes, lizards have a tympanum, located ventrocaudal to the eye, and a middle ear .
  • Many males will have large amounts of ornamentation on their body surface for display purposes, eg the male green iguana, which often has large colored scales on the head and a bluish sheen to the head and neck coloring . Others, such as male anoles, have extendable chin flaps which are often brightly colored and can be ‘flashed’ in display. Some males, such as the male plumed basilisks, have larger nuchal crests than the female.
  • Many lizards, such as the green iguana have a parietal eye; this is a special adaptation on the very top of the skull midway between the eyes. It is connected directly, via neural pathways, to the pineal gland in the brain and it is responsible for informing the lizard about light intensity and daytime lengths; these in turn influence feeding and reproductive behavior.
  • In the tuatara, which is found in New Zealand, a primaeval lizard in its own class of the reptile family, this parietal eye has a vestigial lens within it.

Musculoskeletal system

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Cardiovascular system

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Respiratory system

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Digestive system

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Excretory system

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Lymphatic system

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Reproductive system

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Nervous system

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Sense organs

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Further Reading

Publications

Refereed papers

Other sources of information

  • Wilson B (2017) Lizards. In: Exotic Animal Medicine for the Veterinary Technician. 3rd edn. Eds: Ballard B & Cheek R. Wiley-Blackwell. pp 95-136.
  • Girling S J (2013) Basic Reptile and Amphibian Anatomy and Physiology. In: Veterinary Nursing of Exotic Pets. 2nd edn. Wiley-Blackwell. pp 246-265.
  • Mader D R (2006) Ed Reptile Medicine and Surgery. Saunders Elsevier, USA. pp 1242.

Reproduced with permission from Bonnie Ballard & Ryan Cheek: Exotic Animal Medicine for the Veterinary Technician © 2017, and Simon J Girling: Veterinary Nursing of Exotic Pets © 2013, published by John Wiley & Sons.


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