Thursday, August 30, 2012

Living Fossil: The Dinosaur's Archosaur Relative

A few weeks ago I wrote about a living fossil, the horseshoe crab.  Today I will be going over another type of modern prehistoric creature that is near and dear to my heart, crocodilians.  Crocodilians (including crocodiles, alligators, caimans and gharials) have been wildly successful since the Triassic.  They started to become successful right alongside the first dinosaurs.  Unlike the dinosaurs, however, (many)crocodilians have remained virtually unchanged since the Mesozoic.  Dinosaurs, on the other hand, evolutionarily experimented with countless different body types, sizes and niches only to end up with just one variety adaptable enough to survive into today (birds).

In the workplace I get the pleasure of dealing with the Dwarf Caiman (Paleosuchus palpablrosus), the smallest and most heavily armored member of Crocodilia.

During the Mesozoic era there were crocodilians that were more or less the same as the ones living today.  Some, however, did evolve a bit differently.  There are a number of strange and different kinds of crocodilians on the fossil record.  Some were more land-adapted, some had wildly different skulls for functions scientist can only guess at today and some, like Sarcosuchus and Deinosuchus, grew to epic sizes and more than likely were preying upon dinosaurs much like smaller modern crocodiles prey on land mammals today.

During the late Cretaceous, crocodilian, Kaprosuchus, threatens the dinosaur, Nigersaurus.

Today, crocodiles and their kin remain one of the most adaptable and successful reptiles, but why?  Here is an animal that has remained virtually unchanged for 250 million years.  They must be doing something right

Lets start by looking at a crocodilian's lifestyle.  They don't require much.  They spend time in and out of the water (which doesn't need to be that clean) and tend to be generalist predators all around.  A crocodilian won't hesitate to eat any kind of animal, including rotting carcasses other meat eaters would pass on.  Furthermore, like many reptiles, crocodilians are cold blooded or ectothermic.  Because of this their metabolisms are much slower than an endothermic animals's and therefore don't require as much food in order to stay alive.  In fact, after a large meal, a large crocodile can go to a year's time without eating if it has to.

Come on in!  The water' don't. 

When compared to other modern reptiles like testudians and squamates, crocodilians have a few advantages.  The tough scales on their backs, called scutes, function like solar panels, allowing the animal to absorb energy from the sun and warm the body up much more quickly than most other modern reptiles.  Crocodilians have a four chambered heart and the functional equivalent of a diaphragm.  They also have a one-way breathing system much like their closest living relatives, the birds.  This means that instead of mixing inhaled and exhaled air in the lungs when breathing (like we do) fresh air is continuously being taken through the body (more efficient).  Fun fact: alligators have the most powerful jaws of any living animal ever recorded (over 2,000 pounds per square inch).

Alligator mouth.  Yes, I took this picture.  No, there was no zoom. 

American Alligators (Crocodilus mississipiensus) have recently become the interest of medical doctors because of their immunity to a vast variety of pathogens.  In a lab setting, alligator serum and human serum were both exposed to twenty three types of harmful bacteria including MRSA (methicillin-resistant staphylococcus aureus), E. colli and Salmonella.  The Alligator serum fought off all of them with flying colors.  The human serum only managed to fight off eight.  Furthermore, the protiens in alligator blood were also discovered to be totally resistant to Candida albicans (fungus), HIV and Herpes (viruses).  This could be due to the fact that alligators commonly live in environments where the water isn't exactly the cleanest.  Lets just say if a human were to go wading around in there with any open wounds there is a solid chance that individual would get an infection of some kind.  Alligators, however, get bloody injuries all the time due to fighting amongst themselves for dominance.  Its a fundamental part of their social behavior.  Its not uncommon to see alligators missing body parts from fights with rivals.  Yet despite these seemingly mortal wounds, the alligators almost always heal up no problem even with the bacteria and other nasty pathogen-infested water they are constantly swimming around it.  Jaws, armor and metabolism aside, the crocodilian's immune system very well may be its secret to success.  Sadly, even the mighty crocodilians were found to be sensitive to pollution caused by humans.

Alligator that had lost it's tail in a fight.  The wound healed over no problem.

Who knows?  If scientists manage to sequence the proteins in alligator blood, we may have some powerful new medicine in the future to fight off seemingly incurable diseases!  

Works Cited

Bird, July. Antibiotics from alligators. Nature Publishing Group 8.5 (2008): 326-26.

Merchant, Mark. Differential protein expression in alligator leukocytes in response to bacterial lipopolysaccharide injection. Comparative Biochemistry and Physiology: Genomics and Proteomics 4.4 (2009): 300-04.

Fleshler, David. Alligators' 'ferocious' immune system could lead to new medicines for people. Sun-Sentinel. 14 Aug. 2006.

Avasthi, Amitabh. "Alligator Blood May Lead to Powerful New Antibiotics." National Geographic

Farmer, C. G., and Sanders, K. (January 2010). "Unidirectional Airflow in the Lungs of Alligators". Science 327 (5963): 338–340. doi:10.1126/science.1180219. PMID 20075253.

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