metabolism, energetic demand, and endothermy sara mccutcheon and christine bedore september 25, 2007

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


•Closed respirometer

1 O2 electrode- measure in sealed recirculating tank

• Open respirometer

2 O2 electrodes- before and after chamber


•Circular respirometers

Pros: easy to build affordable

fish can swim freely in circular pattern or rest



Cons: unnatural swimming patternabrasions, exhaustion, ↓ O2 across gills

lack of H2O mixing during rest

require motion sensors, don’t know actualactivity level


•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



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


•Muscle Temperature telemetry (Tm)

harpoon thermistor deep in epaxial RM

measure ∆ Tm as transmitter pulse rate changes

simultaneously measure depth and Ta


•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


•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


•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


•Lab studies + field studies = energy budget

C=M+W+G

C=consumption

M=metabolism

W=waste

G=growth


•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


•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.

metabolism, energetic demand, and endothermy sara mccutcheon and christine bedore september 25, 2007

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