Fish 475: Marine Mammalogy

Transcription

1 Fish 475: Marine Mammalogy Adaptations to Life at Sea I: 19 April 2010 Course website:

2 Major challenges of life at sea for homeothermic animals of terrestrial ancestry Text reading reference: Chapter 3

3 Major challenges of life at sea for homeothermic animals of terrestrial ancestry Hans Thewissen Carl Buell

4 It s COLD

5 It s COLD Global mean temperature of the ocean is ~3.5ºC or ~38.3ºF Heat capacity of water is ~25x heat capacity of air at the same temperature

6 It s DENSE John Schmied

7 It s DENSE Density of water is ~800x density of air at the same temperature John Schmied

8 It s DARK

9 It s DEEP

10 It s DEEP Mean depth of the ocean is ~4,300 m (~14,000 ft) Mean depth of the Grand Canyon is 1,600 m (5,249 ft)

11 It s SALTY

12 It s SALTY The ocean is ~3.5% dissolved salts by weight Columbia University

13 It s UNBREATHABLE

14 It s UNBREATHABLE

15 A brief recap Features of the ocean environment likely to pose difficulties for terrestrially-derived, air-breathing homeotherms: Low temperature High thermal conductivity High density High rate of light absorption by sea water, and by materials dissolved or suspended in sea water High ambient pressure gradient with increasing depth High dissolved inorganic ionic concentrations Lack of opportunity for respiratory gas exchange below the sea surface

16 A simple model for heat flow: Heat Loss Rate = C x SA x T Where: C = Material-specific coefficient of heat flow; SA= Surface area of animal; T= T I T O ; T I = Temperature inside animal; T O = Temperature of surrounding sea water.

17 A simple model for heat flow: Heat Loss Rate = C x SA x T Heat Loss Rate = C x SA x T Strategies for reducing C: Subcutaneous blubber Pelage and air buffers Lanugo

18

19 A simple model for heat flow: Heat Heat Loss Loss Rate Rate = = C C x x SA SA x T x T Strategies for reducing C: Subcutaneous blubber Pelage and air buffers Lanugo

20

21 A simple model for heat flow: Heat Heat Loss Rate Rate = = C x x SA SA x x T T Strategies for reducing C: Subcutaneous blubber Pelage and air buffers Lanugo

22 A simple model for heat flow: Heat Loss Rate = C x SA x T Strategies for reducing T: Counter-current heat exchangers Near external Ambient T Near core T Ocean Core Near external Ambient T Near core T Skin

23 A simple model for heat flow: Heat Loss Rate = C x SA x T Core Core Strategies for reducing T: Blubber Counter-current heat exchangers Skin Air layer Ocean

24 A simple model for heat flow: Veins (cooler) Heat Loss Rate = C x SA x T Strategies for reducing T: HEAT FLOW Artery (warmer) Counter-current heat exchangers

25

26 A simple model for heat flow: Capillary bed Heat Loss Rate = C x SA x T Strategies for manipulating T: Peripheral circulatory shunts Shunt Shunt sphincter (closed) Shunt sphincter (open) CASE 1: Warm conditions or excess internal heat

27 A simple model for heat flow: Capillary bed Heat Loss Rate = C x SA x T Strategies for manipulating T: CASE 2: Peripheral circulatory shunts Cool conditions or shortage of internal heat Shunt Shunt sphincter (open) Shunt sphincter (closed)

28 THE DIVING PHYSIOLOGY OF BOTTLENOSE DOLPHINS (TURSIOPS TRUNCATUS) III. THERMOREGULATION AT DEPTH Williams et al Fig. 1. Infrared thermograph of the fluke of a bottlenose dolphin. Warm areas (denoted by white and red) correspond to large blood vessels that traverse the width of the underside of the fluke. Note the comparatively cool peduncle area shown in blue. The color bar at the bottom denotes 0.1 ー C differences in surface temperature per gradation. Fig. 2. Heat flow during resting, diving and post-dive periods for adult bottlenose dolphins. Values for the dorsal fin (A) and flank (B) are compared.

29 A simple model for heat flow: Heat Loss Rate = C x SA x T Strategies for reducing SA effect: Consider heat loss rate per unit of animal biomass: HLR/mass = (C x SA x T)/mass; or: HLR/mass = C x [SA/mass] x T If we assume that animal volume can serve as a surrogate for animal mass, then: HLR/volume = C x [SA/volume] x T

30 A simple model for heat flow: Heat Loss Rate = C x SA x T Strategies for reducing SA effect (continued): Consider heat loss rate per unit of animal biomass: HLR/volume = C x [SA/volume] x T If we define r as the mean radius of a marine mammal (i.e., the mean distance from the centerpoint of the animal s body to any point on the skin surface), then: Surface area will be proportional to r ~2, and Animal volume will be proportional to r ~3 Thus, as animal size increases, r will also increase, and [SA/volume] will change by the factor 1/r, meaning: As animal size increases, HLR per unit volume decreases. As a result, increased body size may be selected as a strategy for heat conservation.

31 A simple model for heat flow: Best example of selection for large body size as a method for heat conservation: Sirenians

32 Special applications for counter-current heat exchangers Pabst et al 1995