Diving vertebrates

Question 1

What is the Arapaima gigas?

Answer 1

An amazonian fish that will drown in around 10 mins

if denied access to the water surface.

I has a swimbladder modified for breathing air and its gills are completely non-functional for aquatic respiration.

Question 2

Amphibian circulation consists of a three-chambered heart.

Oxygenated and deoxygenated blood are kept seperate by a spiral valve in the conus arteriosus.

Oxygen saturation is around 86% in the aorta and only 47% in the pulmocutaneous.

Blood flow is shunted between lungs or skin in the pulmocutaneous circuit depending on aquatic oxygen tension.

In hypoxic water, blood flow to the skin is shut off to reduce loss to the water.

Question 3

Diving in Marine Iguanas

• Iguanas are Poi-kilo-thermic
• Animals undergo a cyclical pattern of dives interspered with periods of sun basking on shore.

During dives

-Peripheral vasoconstriction

Reduces heat loss to water

Reduces aerobic metabolism in swimming muscles

-Bradychardia

Reduced metabolic cost

Question 4

The heart of a crocodile is almost completely divided except for the _______ of _______ between the left and right aortae.

Answer 4

Foramen of Panizza

Question 5

When the crocodile is breathing air, greater pressure in the ____ ventricle forces the _____ ventricular semilunar valve closed.

Deoxygenated blood is diverted to the _____

Oxygenated blood shunts from the ________ through the ______ on _____ to the _______

Answer 5

in the left ventricle

forces the right ventricular semilunar valve closed

diverted to the lungs

Oxygenated blood shunts from the left (right aorta) through the Foramen on Panizza to the right (left aorta)

Question 6

Improving diving is about improving oxygen storage

Increasing lung volume mostly increases nitrogen storage

It is much more efficent to increase 02 by?

Answer 6

• Increasing red blood cell mass
• Increasing blood volume (doping)
• Increasing spleen storage capacity

Increasing O2 storage on myoglobin in muscles

(Storing oxygen not nirogen)

Question 7

Mammalian divers discovered in 2013 that their myoglobin..

Answer 7

..carries a net positive surface charge that allows these animals to accumulate very large concentrations of myoglobin in their muscles. This surface charge causes electrostatic repulsion that prevents myoglobin molecules sticking together.

Question 8

Yellow fin tuna

Food down at 250m, why not just stay there?

Answer 8

• Yellowfin tuna is tropical species
• Dives down to 1200m
• Water 28oc at surface (warm)
• 1000m down temp is 5oc
• Fish is warm bodied, can maintain muscle temperature well
• Tunas heart is close to surface of body (chest outside wall)
• When fish gets to 5oc water, muscles stay warm the heart cools down. Supply of blood to fuel the muscle in order for fish to swim efficently is affected. Heart cools down, heart rate drops, poor swimming and feeding as a result.

Fish comes back to surface in order to warm back up and get the heart warm enough to start pumping blood fast enough again to supply oxygen to the muscles. Not that it needs to come to the surface in order to breathe oxygen.

Question 9

The Weddell Seal

Lives in Antartica, live right next to research station.

Two types of dives, what are they?

Answer 9

Deep

(short, aerobic, feeding dives)

Shallow

(long, shallow, anaerobic, exploratory dives/territory/breathing holes)

Question 10

Adaptations for diving in the weddell seal

Answer 10

• Large blood volume (stores O2) 2x as much as human
• Myoglobin in muscles (stores O2) 10x more than human
• Use stored O2 rather than air (No bends, narcosis/toxicity)
• Large red blood cell storage in the spleen (released during dive)

Question 11

Weddell Seal

No big breath, exhale before submerge

Why not take a big breath?

Answer 11

• Although whales breathe in before they dive, the lungs compress at depth and air is forced into non-respiratory passages
• A buoyancy aid
• Most oxygen is carried on haemoglobin in the blood and on myoglobin in the muscles.

Question 12

Conserving oxygen during the dive

Diving mammals reduce oxygen use by..

Answer 12

The diving reflex

• Bradychardia
• Peripheral vasoconstriction

Having efficient underwater locomotion

• Streamlined shape
• Efficent propulsion - gliding dives/effortless
• Neutral buoyancy

Question 13

The Diving (trigeminal) Reflex

Answer 13

• Bradycardia
• Apnoea
• Peripheral blood vessels constrict

Question 14

Blood flow to non-essential areas is almost totally shut down during dive. Name the non-essential parts.

Answer 14

• Diaphragm
• L ventricle
• Kidney
• Liver
• Intestine
• Skeletal Muscle

(Brain increases)

Question 15

Countercurrent vasculature in extremities reduces heat loss and regional heterothermy reduces oxygen yse in extremeties.

Answer 15

Not only physiological adaptations, also anatomical.

Dorsal fin on dolphin arrangment of blood vessels where arteries surrounded by veins acts as heat exchanger.

Hot blood coming from the body core will exchange heat with the cold blood coming back from the veins in order to pre cool the arterial blood before it gets back to the edge of the dorsal.

Flipper has large surface area which acts as heat sink sending heat out into the water to minimise that we have counter current heat exchange.

Question 16

Seals have a reduced __________ ________ to CO2 in brain and more hypoxia tolerant.

Answer 16

chemoreceptor sensitivity

In humans, when CO2 builds up in the blood it drives respiration. When CO2 gets to a certain critical threshold, you can’t stop yourself from breathing, If you are under water you die.

Question 17

Large body mass reduces what?

Answer 17

Metabolic rate

Question 18

Using stored oxygen rather than air reduces what?

Answer 18

The bends, narcosis, toxicity.