Blood shunt / PFO?
review of PFO:
http://forums.deeperblue.com/general-freediving/41162-pfo-possible-contributor-blackouts.html
“Patent foramen ovale – a flap valve between the right and left upper chambers of the heart is present in up to 25-37 per cent of people." Interesting because that's about the same proportion of Europeans (or Eurasians) that have Photic Sneeze Reflex (PSR), part of what I think is vestigial from the ancestral human apneic dive-foraging cycle (Aquaphotic Respiratory Cycle). http://forums.deeperblue.com/freediving-science/79552-diving-surfacing-efficiently.html
I guess this is the same or similar valve action in crocs and humans (embryologically, today most people close the PFO when very young). Perhaps digestion and diving (eating/food processing while in oxygen conserving state) selected for this shunting, not "long dives" per se; [MAYBE] this fits with seals & crocs needing to eat quickly (due to intra-specific competition) so eating underwater would be advantageous, while sea otters eat at the surface while backfloating so they would not likely have this shunting. Human ancestors may have done both, suction feeding oysters at submersed reefs and cracking and eating crabs while backfloating (in addition to dry-land foods: fruit, nut, some meat)
Would be interesting to know whether or not non-carnivorous apneic-diving marine iguanas and non-diving carnivorous komodo dragons have this shunting.
===
Mystery Solved: How Can a Crocodile Eat a Cow at Once? - The shunting system - Softpedia
Now, scientists have solved the mystery of this amazing ability. A research to be detailed in the March-April issue of the journal "Physiological and Biochemical Zoology" reveals how a heart valve that crocodiles can control neurologically lets blood bypass the lungs and go through a special aorta directly to the stomach, boosting by 10 times the speed of gastric acid, at a rhythm not found in other animals.
"Crocodiles, alligators and other crocodilians all share this ability," said biologist C. G. Farmer of the University of Utah, who discovered this phenomenon.
"It's been known for many years that reptiles can shunt blood past the lungs, but the function has not been understood," Farmer told LiveScience.
Scientists had believed the shunt was meant for long dives, but no research proved that.
"Some people in the field are pretty sure this is explained by diving, so I think they're going to be surprised," Farmer said.
Farmer and her team surgically impeded some crocodiles' valve to skip the blood flow of the lungs. It appeared that crocodiles with an intact valve secreted gastric juices at a significantly increased rate. Blood skipping the lungs is rich in carbon dioxide, otherwise released in the lungs.
CO2 enters in the composition of gastric juice, accelerating its production, and the large amounts of gastric juice enable the crocs to properly digest large quantities of food.
"If any animal eats a meal that size, they can't process it immediately. As the meal is being broken down, the stomach holds on to the bulk of the food and sends little bits on to the intestine. If they weren't able to secrete a lot of acid in their stomachs, the food there would putrefy due to the overgrowth of bacteria. Eating big meals infrequently has selected for this ability," said Farmer.
The high acidity in the stomach of the crocodile enables the animal to dissolve even the bones of prey, and also hooves or feathers. Only teeth cannot be attacked by these powerful juices. The neurologically-controlled valve is specific to crocodilians, but a shunting system of any type may be encountered in other reptiles too for passing blood past the lungs. This should exist at least in the case of snakes and monitor lizards.
"It would be interesting to see if Burmese pythons also use the system for digestion, because they can eat meals that weigh more than 100% of their body mass. They do have a shunt system. It's just hard to study for technical reasons," said Farmer.
[Note: I'm not familiar with the link source Softpedia.]
PBZ left side panel: Sea Snakes need freshwater, alligators shunt, baby seals burn blubber to warm up
University of Chicago Press - Cookie absent
PFO in pigs similar to human in prevalence and form (pigs have MDR, thick SC fat, some wild pigs swim from island to island, eat fish and mollusks, but very generalized omnivorous diet, like humans.)
http://www3.interscience.wiley.com/journal/113480907/abstract?CRETRY=1&SRETRY=0
PFO in young bearded seals (non-weaned or self-sufficient hunting? Ontologically, the PFO closure in growing seals may indicate that their ancestors dove with non-collapsing lungs while feeding, but modern seals with collapsing lungs may get no advantage from PFOs.)
http://www.biomedexperts.com/Abstra...vale_in_bearded_seal_Erignathus_barbatus_pups
review of PFO:
http://forums.deeperblue.com/general-freediving/41162-pfo-possible-contributor-blackouts.html
“Patent foramen ovale – a flap valve between the right and left upper chambers of the heart is present in up to 25-37 per cent of people." Interesting because that's about the same proportion of Europeans (or Eurasians) that have Photic Sneeze Reflex (PSR), part of what I think is vestigial from the ancestral human apneic dive-foraging cycle (Aquaphotic Respiratory Cycle). http://forums.deeperblue.com/freediving-science/79552-diving-surfacing-efficiently.html
I guess this is the same or similar valve action in crocs and humans (embryologically, today most people close the PFO when very young). Perhaps digestion and diving (eating/food processing while in oxygen conserving state) selected for this shunting, not "long dives" per se; [MAYBE] this fits with seals & crocs needing to eat quickly (due to intra-specific competition) so eating underwater would be advantageous, while sea otters eat at the surface while backfloating so they would not likely have this shunting. Human ancestors may have done both, suction feeding oysters at submersed reefs and cracking and eating crabs while backfloating (in addition to dry-land foods: fruit, nut, some meat)
Would be interesting to know whether or not non-carnivorous apneic-diving marine iguanas and non-diving carnivorous komodo dragons have this shunting.
===
Mystery Solved: How Can a Crocodile Eat a Cow at Once? - The shunting system - Softpedia
Now, scientists have solved the mystery of this amazing ability. A research to be detailed in the March-April issue of the journal "Physiological and Biochemical Zoology" reveals how a heart valve that crocodiles can control neurologically lets blood bypass the lungs and go through a special aorta directly to the stomach, boosting by 10 times the speed of gastric acid, at a rhythm not found in other animals.
"Crocodiles, alligators and other crocodilians all share this ability," said biologist C. G. Farmer of the University of Utah, who discovered this phenomenon.
"It's been known for many years that reptiles can shunt blood past the lungs, but the function has not been understood," Farmer told LiveScience.
Scientists had believed the shunt was meant for long dives, but no research proved that.
"Some people in the field are pretty sure this is explained by diving, so I think they're going to be surprised," Farmer said.
Farmer and her team surgically impeded some crocodiles' valve to skip the blood flow of the lungs. It appeared that crocodiles with an intact valve secreted gastric juices at a significantly increased rate. Blood skipping the lungs is rich in carbon dioxide, otherwise released in the lungs.
CO2 enters in the composition of gastric juice, accelerating its production, and the large amounts of gastric juice enable the crocs to properly digest large quantities of food.
"If any animal eats a meal that size, they can't process it immediately. As the meal is being broken down, the stomach holds on to the bulk of the food and sends little bits on to the intestine. If they weren't able to secrete a lot of acid in their stomachs, the food there would putrefy due to the overgrowth of bacteria. Eating big meals infrequently has selected for this ability," said Farmer.
The high acidity in the stomach of the crocodile enables the animal to dissolve even the bones of prey, and also hooves or feathers. Only teeth cannot be attacked by these powerful juices. The neurologically-controlled valve is specific to crocodilians, but a shunting system of any type may be encountered in other reptiles too for passing blood past the lungs. This should exist at least in the case of snakes and monitor lizards.
"It would be interesting to see if Burmese pythons also use the system for digestion, because they can eat meals that weigh more than 100% of their body mass. They do have a shunt system. It's just hard to study for technical reasons," said Farmer.
[Note: I'm not familiar with the link source Softpedia.]
PBZ left side panel: Sea Snakes need freshwater, alligators shunt, baby seals burn blubber to warm up
University of Chicago Press - Cookie absent
PFO in pigs similar to human in prevalence and form (pigs have MDR, thick SC fat, some wild pigs swim from island to island, eat fish and mollusks, but very generalized omnivorous diet, like humans.)
http://www3.interscience.wiley.com/journal/113480907/abstract?CRETRY=1&SRETRY=0
PFO in young bearded seals (non-weaned or self-sufficient hunting? Ontologically, the PFO closure in growing seals may indicate that their ancestors dove with non-collapsing lungs while feeding, but modern seals with collapsing lungs may get no advantage from PFOs.)
http://www.biomedexperts.com/Abstra...vale_in_bearded_seal_Erignathus_barbatus_pups
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