Neuroprotecting globins in the marine mammal brain Photo credit: democraticunderground.com

What adaptations do they use in order to hold their breath for such a long, long time?

Mammalian breath hold capabilities ( in minutes) Human*1 Polar bear1.5 Sea otter5 Porpoise15 Seal15-28 Greenland Whale60 Sperm whale90 Bottlenose whale120 *Crazy Swiss man, Peter Colat, 19 min. 21 s Photo credit: news.discovery.com

Photo credit: puertogaleradive.com Basis for this field of research: Energy we think they gain from one breath << Energy we think they spend while submerged

Basis for this field of research: Energy we think they gain from one breath << Energy we think they spend while submerged If above is true, you would expect: Evidence heavy reliance on anaerobic metabolism Photo credit: puertogaleradive.com

Basis for this field of research: Energy we think they gain from one breath << Energy we think they spend while submerged If above is true, you would expect: Evidence heavy reliance on anaerobic metabolism Photo credit: puertogaleradive.com

Basis for this field of research: Energy we think they gain from one breath << Energy we think they spend while submerged Photo credit: puertogaleradive.com Then, above statement must not be true…

Basis for this field of research: Energy we think they gain from one breath << Energy we think they spend while submerged Photo credit: puertogaleradive.com Then, above statement must not be true… Now what?

Basis for this field of research: Energy we think they gain from one breath << Energy we think they spend while submerged Photo credit: puertogaleradive.com Then, above statement must not be true… Now what? Look for adaptations!

What researchers found: 1870 Paul Bert - limits  blood volume 1930s & 1940s - Body size Total blood volume RBC mass Hematocrit Muscle [myoglobin]

Figure credit: Hochachka and Somero 2002 What researchers found: 1870 Paul Bert - limits  blood volume 1930s & 1940s - Body size Total blood volume RBC mass Hematocrit Muscle [myoglobin]

Photo credit: doc.govt.nz Dive response concept: Apnea Bradycardia Peripheral vasoconstriction Hypometabolism Helps us understand balance: Energy in one breath Energy used in prolonged dive

Interrelatedness of dive response components: Apnea  Bradycardia

Interrelatedness of dive response components: Apnea  Bradycardia (even in humans)

Interrelatedness of dive response components: Apnea  Bradycardia  Drop in cardiac output (CO = stroke volume x heart rate (vol/min))

Drop in arterial BP Interrelatedness of dive response components: Apnea  Bradycardia  Drop in cardiac output 

Drop in arterial BP Interrelatedness of dive response components: Apnea  Bradycardia  Drop in cardiac output  X

BP remains stable Interrelatedness of dive response components: Apnea  Bradycardia  Drop in cardiac output while Vasoconstriction 

Figure credit: Hochachka and Somero 2002

BP remains stable Interrelatedness of dive response components: Apnea  Bradycardia  Drop in cardiac output while Vasoconstriction   Hypometabolism

BP remains stable Interrelatedness of dive response components: Apnea  Bradycardia  Drop in cardiac output while Vasoconstriction   Hypometabolism (energy saved in bypassing non-vital organs  2-3ºC drop in body temperature)

How would you monitor these responses?

Heart monitors Backpack cameras Lactate dehydrogenase levels Figure credit: Davis et al. 1999

Figure credit: Kooyman et al. 1981

Figure credit: Hochachka and Somero 2002

Photo credit: ctap4.org Dive response concept: Apnea Bradycardia Peripheral vasoconstriction Hypometabolism How do these relate to: Body size Total blood volume RBC mass Hematocrit Muscle [myoglobin]

Figure credit: Williams et al Behavioral adaptations: Dive duration Gliding Resting

Proposing a new adaptation for the list…

Photo credit: wikipedia.com Globins Proteins with heme group Involved in oxygen binding and transfer Hemoglobin (Hb) Myoglobin (Mb) Cytoglobin (Cb) Neuroglobin (Nb)

Photo credit: brainviews.com Cerebral cortex Thin sheet of neural tissue Plays role in: Memory Attention Perceptual awareness Thought Language Consciousness

Researchers still think blood oxygen levels in diving mammals are too low to sustain activity…

Williams et al Hypothesis: Enhanced levels of neuroprotecting globins are an additional adaptation for a diving lifestyle

Williams et al Methods: Group globins: Circulating (Hb) Resident (Cb and Nb) Measure in cerebral cortex of 16 species Running, swimming, diving Prolonged mortality events Spectrophotometric determination mRNA expression

Williams et al Results: Globin levels correlated with activity group Figure credit: Williams et al. 2008

Williams et al Results: Hb and RNGs significantly higher in diving marine mammals compared to terrestrial species Figure credit: Williams et al. 2008

Williams et al Results: RNG levels inversely correlated with dive duration Figure credit: Williams et al. 2008

Williams et al Discussion: Elevated RNG and Hb levels are adaptations for activity type Enhance diving response Cope with low oxygen levels during prolonged dives Circulating and resident globins provide complementary support

Questions for Discussion How do you expect the following to interact with and effect adaptive globin responses? Body size Phylogenetic history Habitat Activity level What does hypoxia really mean? Post mortem sampling concerns… Standardize globin concentrations to total blood volume?