1. Aspects of Marine Animal Physiology
Respiration
Gaseous Exchange
Osmoregulation

2. Basics
Aerobic respiration: process by which almost all living organisms obtain the energy they need
Oxidation of organic molecules (glucose)
glucose + oxygen  carbon dioxide + water
This is a simplified version and does not show all the intermediate rxns involved
Key: respiration converts chemical energy of glucose into a form which can be used by organisms (for muscle contraction, growth, etc)
All heterotrophic organisms obtain the organic molecules either directly or indirectly from autotrophic organisms (food chains/webs)

3. Limits to Diffusion
Organisms need to exchange materials with their environment
Include respiratory gases (O2 and CO2), nutrients, and excretory products (waste substances produced as result of metabolism)

4. In relatively small and simple organisms (protozoa), exchange takes place across entire body surface
As organisms increase in size and complexity, there are specialized exchange surfaces such as lungs or gills (adapted for the exchange of materials)

5. Surface Area to Volume Ratio
As the size of an organism increases, it’s surface area decreases in relation to its volume
Very small organisms have a relatively large surface area in relation to their volume

6. Why Cells Aren’t Big
All organisms need to exchange substances such as food, waste, gases and heat with their surroundings.
These substances must diffuse between the organism and the surroundings.
The rate at which a substance can diffuse is given by Fick's law:
Rate of Diffusion  = surface area x concentration difference
distance

7. Why Cell’s Aren’t Big Investigation
The rate of exchange of substances therefore depends on the organism's surface area that is in contact with the surroundings.
The requirements for materials depends on the volume of the organism, so the ability to meet the requirements depends on the surface area : volume ratio.
As organisms get bigger their volume and surface area both get bigger, but volume increases much more than surface area.

8. Growing cells 1µm 2µm 3µm 4µm 5µm 6µm SA/V Ratio Demonstration
Why it's REALLY Important

9. How are surface area and volume affected by growth?
SA/V
Volume
/µm3
Surface area
/µm2
Size
/µm 1 2 3 4 5 6 6 24 54 96
150
216 1 8 27 64
125
216 6 3 2
1.5
1.2 1

10. Results
This means that diffusion over the surface of a large organism may be insufficient to meet it’s needs
Diffusion of respiratory gases into and out of cells would be too slow
Some larger organisms are flattened (which is an adaptation to increase their surface area)
Most complex organisms have specialized exchange surfaces (lungs and gills)

11. Transport Systems in Large Mammals
There is an exchange of materials between organisms and their environment; there is also a need for transport of materials within
Oxygen and nutrients transported to respiring tissues, CO2 and wastes are removed
In many small organisms, transport occurs by diffusion or active transport
In larger organisms – the distances are too great and diffusion alone is too slow

12. Large animals have internal transport systems to ensure that substances are delivered efficiently to cells and tissues and wastes are transported away
Usually consists of blood, pumped around the body by one or more muscular hearts
Fish have a single circulatory system
Blood pumped from heart to gills; blood then flows around the rest of the body before it is returned to the heart

13. Life in Water Atmospheric air = 21% oxygen
Concentration of DO much lower in water
Solubility of oxygen in sea water is rather lower than fresh water (due to presence of dissolved salts in sea water)
Solubility of oxygen also decreases as the temperature increases

14. [DO] in sea water at equilibrium with atm/cm3 oxygen per dm3
Temperature /°C
[DO] in sea water at equilibrium with atm/cm3 oxygen per dm3
7.97 10
6.35 15
5.79 20
5.31 30
4.46

15. Larger, more complex animals have a specialized gas exchange surface
Many small marine animals (cnidarians) obtain oxygen they require by diffusion across their body surface
Larger, more complex animals have a specialized gas exchange surface
Often associated with a transport system for respiratory gases etc.

16. Majority of aquatic animals have gills
Large SA for diffusion of respiratory gases
Highly active fish have relatively large SA compared to slower fish
Also have respiratory pigments (hemoglobin and hemocyanin)
High affinity for oxygen
Assist in the uptake of oxygen from environment

17. Coral polyps (Cnidaria) have no specialized gas exchange organs
Do have a large surface area
Diffusion across body wall obtains enough O2
Gas exchange also occurs across the surface of their gastrovascular cavity

18. Pumped Ventilation
Many bony fish maintain almost constant flow of water through gills (ie: grouper)
Achieved by pumping action of the mouth and operculum
Water is drawn into mouth as the volume of the oral cavity increases (think of using a straw)
Water is then drawn through the gills by the action of the opercular covers
they increase the volume of the opercular cavity
Results in a lower pressure than in the oral cavity

19. Ram Ventilation
Tuna swim continuously with mouth open to maintain a constant flow of water over gills
Fish alter the degree of mouth opening during ram ventilation to keep drag to the minimum
Some species (mackerel) change from pumped to ram ventilation as their swimming speed increases to between 0.5 – 0.8 m/sec
Reduces energy cost of maintaining opercular pumping at higher swimming speed

20. Ram Ventilation
Pumped Ventilation

21. Many marine animals maintain a different concentration of ions in their body fluids from the surrounding sea water
As seen in the table, concentrations of ions of the two inverts are similar to those of water
[ions] in blood plasma of toadfish, eel, and salmon are much less than seawater
Useful site

22. Concentration of Ions in Seawater Compared to the Fluids of Animals
Sample
[Solute]/millimoles per dm3
Na+ K+
Sea water
Approx 450 10
Mussel (body fluid)
474 12
Jellyfish (body fluid)
10.7
Toadfish (plasma)
160 5
Eel (plasma)
177 3
Salmon (plasma)
212

23. Vertebrates vs Invertebrates
Most marine inverts are osmoconformers: the concentration of solutes in their body fluid is the same as the surrounding sea water
This means water enters and leaves equally, no overall change in water content of organisms
Marine verts with osmotic concentrations of solutes lower than that of seawater lose water by osmosis
Require mechanisms to maintain their body solute and water content

24. Osmoregulation
Osmoregulation: process by which living organisms maintain the solute and water content in their blood and body fluids
Marine bony fish (teleosts) have an internal solute concentration approx 1/3 of sea water

25. Osmoregulation in a Marine Bony Fish
Drinking sea water
Water and some ions lost in urine
Na+ and Cl- ions secreted by gills
Water lost from gills by osmosis

26. Osmoregulation Marine bony fish drink sea water
Excess salts in water are absorbed in intestine
Sodium and chlorine ions are actively secreted by chlorine secretory cells (present in gills)
Process requires energy (provided by respiration)

27. Osmoconformers
Most marine inverts (including mussels) are osmoconformers
Internal osmotic concentration is the same as their surroundings
Their internal concentrations of individual solutes are not necessarily the same as in sea water
Indicates they have the mechanisms to regular their internal solute concentrations

28. Concentrations of ions in the body fluid of a mussel and sea water
Sample
Concentration of ions/millimoles / kg of water
Na+
Mg2+
Ca2+ K+
Cl-
Mussel
474
52.6
11.9
12.0
553
Sea water
478.3
54.5
10.5
10.1
558.4

29. Eurohaline
Organisms able to tolerate a range of salinities (such as estuarine conditions)
Shore crab Carcinus maenas is common in much of world can tolerate salinities down to 6 ppt
Species of fish which migrate from sea into fresh water (including salmon, eels)
Use different mechanisms to control [ions] in their cells in their different environments
When a salmon migrates into freshwater, the active ion transport in the gills changes direction
Stenohaline: everybody else (limited tolerance)