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Metabolism, Energetic Demand, And Endothermy
Sara McCutcheon and Christine BedoreSeptember 25, 2007
Introduction- Respiration
Buccal ventilation
Ram ventilation
Obligate ram ventilation
Introduction- Muscle
Red muscle (RM) v. White muscle (WM)
RM WMaerobic/oxidative anaerobic/glycolyticfast-twitch slow-twitchhigh-power sustained burst swimming swimming intermediate sustained
swimming
RM WM
Introduction- Thermoregulation
Ectothermy
• body temp ~ ambient (Ta)•most elasmobranchs
Endothermy
• body regions > Ta
• local metabolic heat production• muscles, brain, eyes, stomach• cruising, pelagic species (Lamnids and Alopids?)
Introduction- Temperature Coefficient
Q10:
• metabolic rate change/10 C change in T⁰ a
• Q10= (MR1/MR2) (10/T
2-T
1)
Metabolic Rate
Specific Dynamic Action (SDA)
• metabolic cost of digestion/assimilation
• depends on prefeeding energy, starvation time, activity level
• SDAelasmos ~ SDAteleosts: 15%-20% of metabolism
Metabolic Rate
Standard Metablic Rate (SMR)
• MR-SDA of “resting” fish
• species that rest- direct measurement
• obligate ram ventilators-indirect measurement
Metabolic Rate
Ectotherm SMR
• ↓ Ta & ↓activity = ↓ VO2 = ↓ SMR
• ↑ Ta & ↑ activity = ↑ VO2 = ↑ SMR
• highest- obligate ram ventilators
• highest measured= ½ kg, 28 C ⁰ C. acronotus239 mg O2∙ kg-1 ∙ h-1
Metabolic Rate
Batoid SMR
• SMRbatoid ~ SMR<active, cool H2O, similar size sharks
• High Q10: big ∆MR/10 C⁰
behavioral thermoregulation?
cool H2O ↓ energy demand
exploit warm H2O for food
Metabolic Rate
Maximum Metablic Rate (MMR)
• >active species=↑ MMR
• ex: Sphyrna lewini v. Triakis semifaciata
Metabolic Rate
Anaerobic Metabolism
• WM
• powers burst swimming- ectothermsex: Prionace glauca
Metabolic Rate
y-axis= enzyme activity at 20 C⁰
Bernal et al., 2003
MR Study Methods- Respirometry
•VO2= oxygen consumption
• Indirect calorimetry: calculate MR by measuring VO2
measure DO ↓ as consumed
•O2 required for aerobic metabolism, therefore good measure of MR
• SMR
MR Study Methods- Respirometry
•Closed respirometer
1 O2 electrode- measure in sealed recirculating tank
• Open respirometer
2 O2 electrodes- before and after chamber
MR Study Methods- Respirometry
•Circular respirometers
Pros: easy to build affordable
fish can swim freely in circular pattern or rest
MR Study Methods- Respirometry
•Circular respirometers
Cons: unnatural swimming patternabrasions, exhaustion, ↓ O2 across gills
lack of H2O mixing during rest
require motion sensors, don’t know actualactivity level
MR Study Methods- Respirometry
•Circular respirometers
MR Study Methods- Respirometry
•Circular respirometers
MR Study Methods- Respirometry
•Swim tunnel respirometers
closed system
treadmill: swimming velocity controlled by H2O flow
active metabolic rate
Brett-type: SIO, developed by Jeff Grahamlarger sharks (juvenile I. oxyrhinchus)H2O temp also controlled
MR Study Methods- Respirometry
•Swim tunnel respirometers
MR Study Methods- Respirometry
•Swim tunnel respirometers
Pros: good for ram ventilators
Cons: requires induction of swimmingstress- handling, confinement
MR Study Methods- Biotelemetry
•Field studies possible
• For accurate measurements, combine lab and field studies
• acoustic telemetry: in lab or fieldphysiological sensors: Tm, HR, vswim, tail beatfrequency (TBF)
then calculate MR
MR Study Methods- Biotelemetry
MR Study Methods- Biotelemetry
•Muscle Temperature telemetry (Tm)
harpoon thermistor deep in epaxial RM
measure ∆ Tm as transmitter pulse rate changes
simultaneously measure depth and Ta
MR Study Methods- Biotelemetry
•Heart Rate (HR) telemetry
Measure HR using EKG to estimate VO2, then calculate MR
Ectotherms: HR↑ linearly with vswim & HR varied with VO2
- not good indicator of MR
modulate stroke volume more than HR
Endotherms: cardiac physiology ~ birds, mammals
maybe can use HR telemetry
MR Study Methods- Biotelemetry
•Swim Velocity (vswim) telemetry
speed sensing transmitters
used by Gruber, Bushnell, & colleagues in the 80s lab and field studies- Negaprion brevirostris
used vswim to calculate MR
1st field derived energy budget for any elasmo
MR Study Methods- Biotelemetry
•Tail Beat Frequency (TBF) telemetry
TBF ↑ with vswim ↑, so reliable indicator of acitivity/MR
Electromyography (EMG)- most common method
Magnetic pivoting vane- as caudal peduncle moves,
vane passes over switch that counts TB
Why study MR and energetics?
•Answer important ecological questions
impact of organisms on their environmentimpact of environment on organism’s survival
• Example: Chris Lowe’s S. lewini studies in Kane’ohe Bay
Determined energy budget for population
S. lewini pups are predominant predator inKane’ohe Bay
Why study MR and energetics?
•Lab studies: (Lowe, 2001)Brett-type swim tunnel respirometer
determined VO2/TB
linear relationship
Why study MR and energetics?•Field studies: (Lowe, 2002)
tracked pups in the bay with TBF acoustic transmitters
determined normal TBF
MR Study Methods- Biotelemetry
•Lab studies + field studies = energy budget
C=M+W+G
C=consumption
M=metabolism
W=waste
G=growth
MR Study Methods- Biotelemetry
•Lab studies + field studies = energy budget
• Simplified data for an average pup (760g, 26⁰C)
M= 72 kJ/day
W= 27% of C
G= 18g/day
Therefore, C=242 kJ/day
MR Study Methods- Biotelemetry
•Application:S. lewini pups- major predator in Bay
huge demand on ecosystem
water temp↑ in summer = MR↑ in summercal content of primary prey is low MR↑ + ↓ cals = ↑ mortality in summer
water temp ↓ in winter = MR ↓ in winter ↑ G, ↓ competition
so- ↓ prey= ↓ S. lewini population?
Literature CitedBlock, B.A., and F.G. Carey. 1985. Warm brain and eye temperatures in sharks.
J. Comp. Physiol. B. 156: 229-236.
Carlson, J.K., K.J. Goldman, and C.G. Lowe. 2004. Metabolism, energetic demand,and endothermy. Pp. 203-224 in Biology of Sharks and Their Relatives.(J.C. Carrier, J.A. Musick, and M.R. Heithaus, eds.). CRC Press, Boca Raton
Goldman, K.J. 1997. Regulation of body temperature in the white shark, Carcharodon carcharias. J. Comp. Physiol. B. 167: 423-429.
Lowe, C.G. 2001. Metabolic rates of juvenile scalloped hammerhead sharks (Sphyrnalewini). Marine Biology 139:447-453.
Lowe, C.G. 2002. Bioenergetics of free-ranging juvenile scalloped hammerheadsharks (Sphyrna lewini) in Kane’ohe bay, Oahu, HI. J. Exp. Marine Biol.Ecol. 278:141-156.
Wolf, N.G., P.R. Swift, and F.G. Caery. 1988. Swimming muscle helps warm the brain oflamnid sharks. J. Comp. Physiol. B. 157: 709-715.