True sea snakes (Family Hydrophiidae) have a range of characteristics that facilitate dives of long duration. Identify FOUR such characteristics. Briefly explain the significance of each of these four characteristics.

Question 1

Explain the significance of being an excellent breath holder:

Answer 1

o All snakes have a single long lung- good oxygen storing capacity
o Sea snakes have muscular, rearwards extension of lung (which may help to mix air in part of lung where oxygen is absorbed)

Question 2

Explain why it is beneficial to have relatively low oxygen demands and to be endothermic:

Answer 2

o Do not regulate their core body temperature, mammals use metabolic heat to warm core body temperature and this consumes a large amount of oxygen. In comparison to a mammal a snake has seven times less oxygen demand meaning it can spend seven times longer underwater

Question 3

Explain why it is beneficial to be water-tight when engaging in dives of long duration:

Answer 3

o Around the mouth the scales are known to be particularly tight fitting making them much more watertight
o Nostrils open inwards with a vascular valve that can just be filled with blood in order to close it up

Question 4

Explain why a cardiac shunt is beneficial in breath holding:

Answer 4

• Cardiac shunt (preferentially direct blood to different parts of the body)
o Gives them a bit of flexibility when the oxygen starts to run out