Submitted by Anonymous on Sat, 11/03/2012 - 15:28
Forums
Weddell Seals in the Ross Sea

Hi- As I was reading through Alex's journal entries on the seal's blood & diving adaptations, a couple of questions about the mammalian diving reflex came to mind. 1) You stated that Weddell seals can dive relatively deep- on these deep dives, do they experience a "blood shift"? At what approximate depth does this occur?
2) What is the heart rate of a seal during a shallow dive compared to a deepwater dive? What is the resting heart rate?
Thanks for any input you can give me!

Tammy Orilio Teacher, Marjory Stoneman Douglas High School

Tue, 11/06/2012 - 06:01

Alex Eilers

Great questionsTammy!
Let me touch base with the experts on this one. Will get back to you very soon.
Best - Alex

Wed, 11/07/2012 - 10:40

Alex Eilers

Tammy,
I just heard from Linnea - one of the Graduate Students on the team - and here's what she had to say with regards to you questions.
"1) You stated that Weddell seals can dive relatively deep- on these deep dives, do they experience a "blood shift"? At what approximate depth does this occur?
On any dive, no matter the depth seals decrease peripheral blood flow (to the muscle and most of the organs) to save oxygen for the heart and especially the brain. The blood shift doesn't happen at a particular depth, but is matched to the duration of the dive (see the discussion below).
2) What is the heart rate of a seal during a shallow dive compared to a deepwater dive? What is the resting heart rate?
Resting heart rate is similar to humans- ~60-70bpm. Seals don't control heart rate based on the depth of the dive, rather the duration of the dive. Before a dive, seals take a series of deep breaths, and elevate their heart rate (presumably to load all the tissues with oxygen and rid the body of as much CO2 as possible). When they start their dive, their heart rate drops to as low as 3-4bpm, but usually more like 10bpm and maintain that heart rate throughout the dive. They match the heart rate to the level of exertion during the dive. Which begs the question (that no one knows the answer to yet)- how do they do that? It makes it seem like a seal pre-plans the dive, and knows how long and how deep they will be diving before they even start the dive! When the seals return to the surface, they become tachycardic- increase their heart rate above normal- to quickly replenish oxygen in their body to get ready for the next dive.
They can make some adjustments while diving- another Weddell seal group led by JoAnn Mellish and Marcus Horning (now B470) have recorded heart rate on diving seals while simultaneously recording dive behavior. In one animal, as she approached the breathing hole, she started to increase her heart rate, and something happened (someone already in the breathing hole?), she started diving again, and stopped her heart for 30sec! It then resumed the normal diving heart rate for another 10min (or so) of diving."
How this helps!!!
Alex

Wed, 11/07/2012 - 10:40

Alex Eilers

Tammy,
I just heard from Linnea - one of the Graduate Students on the team - and here's what she had to say with regards to you questions.
"1) You stated that Weddell seals can dive relatively deep- on these deep dives, do they experience a "blood shift"? At what approximate depth does this occur?
On any dive, no matter the depth seals decrease peripheral blood flow (to the muscle and most of the organs) to save oxygen for the heart and especially the brain. The blood shift doesn't happen at a particular depth, but is matched to the duration of the dive (see the discussion below).
2) What is the heart rate of a seal during a shallow dive compared to a deepwater dive? What is the resting heart rate?
Resting heart rate is similar to humans- ~60-70bpm. Seals don't control heart rate based on the depth of the dive, rather the duration of the dive. Before a dive, seals take a series of deep breaths, and elevate their heart rate (presumably to load all the tissues with oxygen and rid the body of as much CO2 as possible). When they start their dive, their heart rate drops to as low as 3-4bpm, but usually more like 10bpm and maintain that heart rate throughout the dive. They match the heart rate to the level of exertion during the dive. Which begs the question (that no one knows the answer to yet)- how do they do that? It makes it seem like a seal pre-plans the dive, and knows how long and how deep they will be diving before they even start the dive! When the seals return to the surface, they become tachycardic- increase their heart rate above normal- to quickly replenish oxygen in their body to get ready for the next dive.
They can make some adjustments while diving- another Weddell seal group led by JoAnn Mellish and Marcus Horning (now B470) have recorded heart rate on diving seals while simultaneously recording dive behavior. In one animal, as she approached the breathing hole, she started to increase her heart rate, and something happened (someone already in the breathing hole?), she started diving again, and stopped her heart for 30sec! It then resumed the normal diving heart rate for another 10min (or so) of diving."
How this helps!!!
Alex