Lecture 11 - Buoyancy, Chemical composition

Question 1

Only animals with ________ have lower metabolic rates at depths beyond the effect of lower temps

Answer 1

Image forming eyes

Question 2

Lower metabolic rates reflect what

Answer 2

Reduction in locomotor abilities of sighted animals (relaxation of selection for locomotion)

Question 3

Buoyancy

Answer 3

Density = weight/volume

Question 4

Seawater density

Answer 4

1.026 g/ml at 20C
1.028 g/ml at 5C
(decreases at higher temps)

Question 5

Negatively buoyant

Answer 5

sinks (higher density than fluid)

Question 6

Positively buoyant

Answer 6

floats (lower density than fluid)

Question 7

Neutral buoyancy

Answer 7

neither sinks nor floats (same density as fluid)

Question 8

Major factors determining composition

Answer 8

1. Effect on density of whole animal
   - swimming costs, patterns of behavior
2. Physical strength
   - strong skeleton and connective tissue require muscles and high activity
3. Energy values of material
   - high value = more food input and E storage required

Question 9

Buoyancy of gelatinous species

Answer 9

Near neutral at all depths

Question 10

Buoyancy of non-gelatinous inverts

Answer 10

Negatively buoyant at shallow depths
Neutral at greater depths
(crustaceans, squids)

Question 11

Buoyancy of fishes (expect mackerels and sharks)

Answer 11

Neutral at all depths

Question 12

Ways of staying up in the water column

Answer 12

1. Swim to stay up ( - buoyant)
2. Achieve or approach neutral buoyancy
   a. reduction of heavy materials (increase water content)
   b. Lower density of the body fluids
   c. Add light materials - lipids
   d. Gases or spaces

Question 13

How does reducing heavy materials change animals?

Answer 13

Increases water content and decreases skeleton and proteins (gelatinous animals)
Limits strength and activity

Question 14

What are the two ways to lower the density of body fluids?

Answer 14

1. Lower the concentration of solutes (teleost fishes)

2. Replace ions in body fluids

Question 15

Two mechanisms for replacing ions to reduce density of fluids

Answer 15

1. Lower molecular weight ions replace heavier ones (lower density due to less weight)
2. Greater partial molal volumes of replacing ions (lower density since the volume of solution for a given weight is increased)

Question 16

Usually ions used to replace other ions

Answer 16

NH4+

Na+

Question 17

3 major subgroups of lipids

Answer 17

1. Phospholipids - Major component of cell membranes
2. Triglycerides - storage fat
3. Wax Esters - long chain fatty alcohol esterified to a long chain fatty acid

Question 18

What animals add lipids to become less dense?

Answer 18

Sharks, teleosts, whales, shrimps, nemertean worms

Question 19

What lipid do portuguese sharks use to become less dense?

Answer 19

Squalene

Question 20

Two ways to uses gases/spaces to decrease buoyancy

Answer 20

1. rigid walls/hard boxes

2. flexible walls/soft boxes

Question 21

Rigid walls

Answer 21

Internal pressure does not need to equal external pressure
Don’t need to be filled to work
Used by cuttlefish, Nautilus, Spirula, Sepia

Question 22

Flexible walls

Answer 22

Internal pressure = external pressure
Need to be filled with gas to work
Examples - fish bladders, siphonophore bladders, kelp gas bladders

Question 23

Disadvantage of hard boxes

Answer 23

Depth limited by crushing of structure

Reverse osmosis can force water into the chamber against osmotic gradient

Question 24

Disadvantages of soft boxes

Answer 24

Vertically migrating animals must remove gas to rise due to danger of embolism
Energetic costs of refilling the bladder limit migrators to shallow depths

Question 25

Swim bladders are absent in pelagic fishes below _____ but are present in _____.

Answer 25

1000 m

near-bottom fishes

Question 26

Elevated lipid in midwater crustaceans and fishes are found only in species from where

Answer 26

Regions of high seasonality (Antarctic, California, Indonesia)

Question 27

Hypothesis for lower lipid content at depth

Answer 27

A. Low food supplies
B. Lack seasonality, variability in food supply
- higher lipids are reserved for seasonal changes in food availability