Marine Mammal Ecology

• Ecology : An attempt to describe and explain the patterns of distribution and abundance of organisms. These patterns reflect the history of complex interactions with other organisms as well as the environment.– Marine mammal ecology is had to get data on. – Marine mammals live in the ocean, which makes

everything harder

• Marine Mammal Protection Act prohibits many techniques typically used to study animals

Marine Mammal Physiology

• Constraints of a Marine Existence– Breath-Holding (Apnea) for

Diving• Marine Mammals are good divers

– Sperm whale can stay under for >2hrs diving 1000-2000m

– Hooded seals exceed 1000m, staying under for >50min

Asphyxia

• Asphyxia: The combined effects of lack of oxygen (hypoxia), increased carbon dioxide, and the accumulation of the products of anaerobic metabolism, such as lactic acid and hydrogen ions

• Aerobic metabolism sustains the brief dives as well as the first parts of the deeper dives, but in longer dives it switches to anaerobic metabolism.

Diving Adaptations

• Oxygen storage– Relative to body size, marine mammal lung

capacities are not much greater than terrestrial mammals.

– Oxygen storage is increased in the blood and muscles and they have more blood than terrestrial mammals.

– The oxygen storage potential in blood and tissue is correlated with the diving abilities of the animal.

Diving Adaptations

• Diving Bradycardia (Decreased Heart Rate)– Low heart rates (5% of predive rate) have

been recorded in phocids– Dolphins can reduce their heart rates from

100 to 12 beats/min.

Diving Adaptations

• Preferential distribution of oxygen to various body tissues during apnea.– Mammalian Diving Response: Regional

vasoconstrictuion within those organs that tolerate a prolonged lack of oxygen. This selective ischemia (when tissues are deprived of circulating blood) lowers the metabolism of those tissues are reduces asphyxia.

– Blood is drawn from areas of less importance to areas of greater importance.

– Sufficient blood pressure is maintained for perfusion of the vital organs, brain and heart.

Under Pressure

• Pressure increases by 1 atmosphere for every 10m of depth– Therefore, the weddell and elephant seals

regularly experience 50 to 100 atmospheres of pressure.

Adaptations to Pressure

• Barotrauma-damage caused by rapid expansion or squeezing of gas spaces that exceeds the structural integrity of tissues. – Lung Squeeze- when the tissues deform to the point

of stress. Limits human breathing dives to about 30m. – Deep diving marine mammals have flexible chest

walls and other structures capable of sufficient collapse to render the lungs airless.

– This keeps air from coming in contact with tissues at high pressures and thus removes the possibility of the “Bends”, Nitrogen Narcosis, Oxygen Toxicity and Hypoxia.

Water and Salt Balance

• Osmosis: The movement of water and salt across a permeable membrane due to a differential in concentration across that membrane.

– If you have a body of high salt concentration (and therefore low water concentration) sitting in an environment of lower salt concentrations (and therefore high water concentration), water will flow into the body and salt will flow into the environment.

– The reverse also occurs.– Can result in dessication (losing too much water), or

plasmolysis (the rupturing of cells that get filled with water).

water molecules protein molecules

semipermeable membranebetween two compartments

Fig. 5-12, p.84

2% sucrose solution

1 liter of distilled water

1 liter of 10% sucrose

solution

1 liter of 2% sucrose

solution

HypotonicConditions

HypertonicConditions

IsotonicConditions

Fig. 5-13, p.85

first compartment

second compartment

hypertonicsolution

membrane permeableto water but not to solutions

fluid volumerises in secondcompartment

hypotonicsolution

Fig. 5-14, p.85

water gain by osmosis

does not drink water

solutes pumped in by cells in gills

water loss in large volume of dilute urine

Freshwater bony fish (body fluids far saltier than surroundings)

Fig. 42-3a, p.740

water loss by osmosis

drinks seawater

solutes pumped out by cells in gills

water loss in very small volume of urine

Marine bony fish (body fluids less salty than surroundings)

Fig. 42-3b, p.740

Osmolality

• Osmolality (osmotic potential) of sea water is about 1000 mOsm/kg. For humans, it’s about 290 to 300 mOsm/kg and for seals it is about 330mOsm/kg

• In order make up the difference marine mammals remove excess salts in very salty uring (2000 to 4000 mOsm/kg)

• Kidneys– Primary site of water conservation as well as

electrolytes and other substances necessary for life– Marine mammals have very large kidneys, that

receives a lot of metabolic energy.

renal capsule

renal vein

renal artery

kidney cortex

kidney medulla

ureter

renal pelvis

Fig. 42-5c, p.742

Fig. 42-6a, p.743

collecting duct (tan)

loop of Henle (yellow)

KIDNEYMEDULLA

KIDNEYCORTEX

Bowman’s capsule

(red)

proximal tubule

(orange)

distal tubule

(brown)

peritubular capillaries threading around tubular nephron regions

Fig. 42-6b, p.743

glomerular capillaries inside Bowman’s capsule

efferent arteriole

afferent arteriole

Fig. 42-7, p.744

glomerular capillaries

proximal tubule distal tubule

CORTEX

MEDULLA

urine outflow from collecting duct into renal pelvis

peritubular capillaries

loop of Henle

incr

easi

ng

so

lute

co

nce

ntr

atio

n

a) Filtration b) Tubular Reabsorption

c) Tubular Secretion

d) Urine