The oil spill in the gulf has me thinking about gators. Have you ever been to a restaurant in New Orleans and enjoyed the tasty alligator selections on the menu? If not, you are missing out. Although I have to admit, they really do taste like chicken. Anyway, you probably know that alligators are cold-blooded because they are ectotherms. But did you know that their hearts are linked to their ability to digest food? It's true! I was just listening to an interview of Dr. Jim Hicks at UC Irvine conducted by Dr. Martin Frank of The American Physiological Society. Many of us are aware that humans and other mammals have a 4-chambered heart. The right side of our hearts is responsible for pumping blood to the lungs to gather oxygen and get rid of carbon dioxide. This oxygen-rich blood then returns to the left side of the heart, which is responsible for sending this blood out the aorta and to the tissues of the body. Did you know that birds and crocodilians (like alligators) also have 4 chambered hearts? Moreover, crocodilians have 2 aorta, that's right, 2. This second aorta exits the right side of the heart (bypassing the lungs) to send the oxygen-depleted (carbon dioxide-rich) blood back out to the body. The goal of Dr. Hicks' research is to determine why crocodilians maintain this ancient morphology.
Since crocodilians are ectotherms they have low metabolisms and their demand for oxygen is lower than ours so this second aorta does not pose much of a problem in the way of supplying oxygen. Dr. Hicks discovered that the carbon dioxide-rich blood that bypasses the lungs travels mainly to the digestive system and is actually used to create hydrochloric acid to aid in digestion! In some animals, Dr. Hicks removed this 2nd aorta and found that they had slower growth rates, a measurement of reproductive ability in crocodilians.
Dr. Hicks also discussed other morphologies of the crododilian heart including their unique valve system that is really different from ours. To hear the full podcast, click here.
Seems to me that shunting blood away from the lungs and toward the body would also speed warming of a gator laying in the sun. The lungs would be radiators and would lose heat from warm blood. Whereas the body, specifically the skin along the back, would be a large solar collector and source of warmth.
Being able to switch blood flow from lungs to body could be used to warm up the gator faster, and/or operate at lower temperatures. Both would extend the time during the day when the gator can productively hunt. A significant advantage.
I love the taste of gator too. Don't get to eat it much but the alligator claws are delicious. It seems to me that everything just taste better fried. I can eat 2 pounds of gator in one sitting.
crocodilians have 2 aorta
the carbon dioxide-rich blood that bypasses the lungs travels mainly to the digestive system and is actually used to create hydrochloric acid to aid in digestion!
If you're trying to follow this and missing a few steps, the HCl secreted by stomach cells comes from:
H2O + CO2 --> H2CO3 --> HCO3- + H+
The hydrogen ion is secreted and the bicarbonate is swapped across the cell membrane for Cl-, which is also secreted. So the idea is that delivering more carbon dioxide to the stomach increases HCl secretion and digestion rates.
growth rates, a measurement of reproductive ability
"growth rates, a measurement of reproductive ability"
It practically impossible to measure reproductive fitness in reptiles, so growth rates are used as a "proxy" indicator of fitness. The idea being, the faster you grow, the sooner you reach reproductive size and maturity, and over a life time, the animal has greater level of fitness, i.e. leaves more offspring (by definition, a feature that increases fitness will be favored by natural selection).