The Sceloporus Magister-SG

The desert spiny lizard (Sceloporus magister)

Ectotherm?

Ectothermic animals include amphibians, reptiles and fishes.These animals cannot control their core temperature physiologically, they exhibit behavioural trends that vary depending on their surroundings. Their bodily temperature depends on the environment they are in, they are unable to generate varying amounts of internal heat through metabolic reactions.

''' Adaptations? '''

The Sceloporus magister lives in the Chihuahuan Desert and Sonoran Desert of North America. Particular habitats include lower slopes, bajadas, plains, and low valleys.As you can imagine, they are exposed to very hot temperatures in the day time and at night the temperature drops. Hence, the “spiny lizards” evolved to cope with these changes.

The Sceloporus magister is nocturnal, they sleep through the night and are active in the day. This means they waste less energy trying to get their body to the optimum temperature again via negative feedback. Laying in the sun with their thinner skin facing up to absorb as much sunlight as possible is also another behavioural adaptation that enables them to regulate their internal core temperature.As they live in hot climates, they burrow under the sand and take advantage of naturally cooler places. They also have thick and scaly skin to prevent water evaporating due to the sun. Since the sand tends to get quite hot, they try to minimise contact by running quickly in all four legs or by running on their back legs only.

They also have lots of blood vessels on their surface of the skin, with vasoconstriction they can restrict blood flow and hence prevent heat radiating out, especially in cold conditions i.e. in the night. Absence of sweat glands means they do not sweat and so heat is not released through latent heat of vaporisation. They retain most of their water from their “dry plant”and insect diet and so this ensures they do not produce too much urine i.e. the volume is low and very concentrated.

Like many desert lizards, the spiny lizard alters their skin colour, at colder times their skin turns black to absorb more heat/solar radiation and in hot conditions their skin turns light colours i.e. white and yellow to reflect the heat.