Interesting Facts

Variation between Individuals:

Due to the great variation of ecosystems that the Western Fence Lizard occupies, different populations with unique physiological characteristics have sprung up to best suit the environment (McMillan et al., 2011).  With this in mind, an experiment has been conducted chronicling how sprinting speed and expression of certain proteins change amongst groups of Western Fence Lizards in differing environments.  The study measured this idea by taking four different samples of lizards; two different geographic locations (north and south) and splitting those locations into high and low elevation in order to provide four unique sampling locations.  Before conducting experimentation, the researchers found that temperature was significantly warmer in the low elevation sample sites as opposed to the high elevation sites (Mcmilan et al., 2011).

At this point the lizards were put onto makeshift racetracks and all of the lizards from each of the locations had theirWestern Fence Lizard on tree sprinting speed recorded by the use of photo gates at 22 degrees Celsius (Mcmilan et al., 2011). It was found that in this control trial, lizards from low elevation areas had a mean sprinting speed that was considerably faster than their high elevation counterparts. The collective pool of lizards were then broken down into control and experimental groups, with the control group having their sprinting speeds measured at 22 degrees Celsius once again, and the experimental group had their speeds measured at 40 degrees Celsius.  It was found during these trials that the sprinting speeds of all groups were negatively affected when exposed to high heat.  In the experimental trials, the lizards taken from higher elevation locations were shown to have a dramatic drop off in sprint speed, with them moving at roughly half the speed as they did during control conditions.  

In addition to sprinting speed, hsp70 (which is a protein designed to combat excessive heat and shield cells from excess stress) levels were measured in the Western Fence Lizards’ as well.  It was found that under control conditions, the levels of hsp70 proteins were relatively consistent in all groups except the southern high elevation group, which displayed high levels of the protein even at a normal temperature.  In addition, the lizards taken from higher elevations displayed higher levels of hsp70 proteins, which demonstrates a negative correlation between sprinting speed and hsp70 concentration.  The high levels of heat denatured the proteins involved in muscle contraction in all lizards, but those lizards from elevated locations suffered the most as they weren’t accustomed to the high level of heat (Mcmilan et al., 2011).  There is a great deal of variability amongst individuals of the same species of Western Fence Lizard. 

 Relationship with Malaria:         

A common source of mortality in all animals is through pathogens.  One of the most deadly human pathogens in the world, malaria, has also been said to be a major problem in the Western Fence Lizard population as well (Eisen, 2001).  Due to this fact, a great deal of experimentation has been done attempting to discover the true connection betweenDead Western Fence Lizard malaria and mortality rates in the Western Fence Lizard.  A malaria causing organism Plasmodium mexicanum, has been known to parasitize the Western Fence Lizard, causing such harmful changes as; damage to host reproduction, decreased ability to store fat (which was previously thought to dramatically increase mortality rates during winter months), as well has having negative repercussions on social behaviors and oxygen carried in red blood cells. All previous scientific experiments involving the Western Fence Lizard and the malaria causing agent were all done in the lab, with the researchers concluding that malaria is very much positively correlated with mortality rates (Eisen, 2001).

Due to the fact that all previous experiments had been conducted in the lab, there was a desire to measure the connection between the two organisms in nature.  With this in mind scientist captured individual lizards’, determining if they have been infected with malaria, marking them accordingly and sending them back out into the wild (Eisen, 2001).  For four years, the lizards’ were collected after every summer and winter with any missing lizards’ being considered dead.  At the end of the four years, it was deduced that there was no statistical significance between the rates of mortality and malaria infection in Western Fence Lizards.  However, while the Western Fence Lizard was able to survive the infection, sexual reproduction as a whole suffered as a result of infection.  In the lizards that were collected, males had smaller testes and showed a lower ability to acquire a mate; and in general reproduction rates for females were down nearly twenty percent (Eisen, 2001).                

 It could be reasoned that the environment played a huge role in this finding; predators or natural events could have caused mortality in individuals that would have died as a result of malaria in the lab (Eisen, 2001).  Also, it’s possible that being in the lab, a foreign environment may have triggered the pathogen to cause more damage.  This reduction of reproductive success means that populations of Western Fence Lizards will become less abundant and diverse.  It looks as if the Western Fence Lizard is able to survive malaria infection at a very high rate; however the reproductive damage caused by the pathogen may be felt in future generations (Eisen, 2001).          

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