Lecture 15 - Cave Fuana, deep sea diversity

Question 1

Caves

Answer 1

Not deep sea habitat, but compared to it

• much less extensive
• often less stable
• relatively transient existence on evolutionary timescale

Question 2

Astyanx mexicanus

Answer 2

Cave fish with eyes in surface pops and no eyes in cave living pops.

Question 3

Cave animals

Answer 3

Usually blind and colorless
Little bioluminescence, none aquatic
Visual animals have lower metabolic rates in caves
-not reduced in amphipods

Question 4

Troglobites

Answer 4

obligate cave dwellers

Question 5

Troglophiles

Answer 5

often live in caves

Question 6

Troglobites vs. troglophiles

Answer 6

1. Larger at maturity
2. Slower growth with asymtotic pattern
3. Long development of eggs
4. Lower metabolic rates
5. Defer reproduction to late in life
6. iteroparous (more bet-hedging)
7. Very low fecundity
8. High Iy
9. Troglobite pops dominated by large individuals

Question 7

Amazon river fish

Answer 7

lack eyes or has reduced eyes
Lack pigment
electric fish
Lives in caves (dark, high productivity, high current, unstable)

Question 8

Cave benthos (for comparison with vents)

Answer 8

Megafuana - readily seen
Near bottom pelagic - larger fraction of biomass often above bottom
Hard bottom - very sparse pop, expect in strong currents
Soft bottom - very high diversity

Question 9

Fossil record evidence for deep sea

Answer 9

Deep sea groups are recent (20 - 100 million years) radiations into the deep sea
Consistent with deep sea anoxia and hypoxia wiping out deep sea fauna
Ancient group probably survived in shallow water and migrated to deep sea

Question 10

Vertical distribution of deep sea benthic communities

Answer 10

1. Species comp changes with depth
2. Very wide vertical distribution of many bathyal species
3. High diversity of meiofauna
4. diversity maximum between 2000 - 3000 m benthic
   (around 1000 m pelagic)
5. Standing stock declines exponentially with depth
6. Often latitudinal gradients in diversity and biomass

Question 11

Why high diversity in deep sea infauna?

Answer 11

1. Stability
2. large area - homogeneous with few barrier to dispersal
3. Patchy food resources from falls
4. Disturbance
   
   • wide variety of microhabitats prevents competitive exclusion from going to completion
5. Competition exclusion avoided with divergent specializations/niches
6. Higher productivity leads to higher diversity
7. Overlap of deeper and shallower fauna

Question 12

Hydrothermal vents - individual vents are…

Answer 12

Small in area
Tremendous biomass, productivity - 100,000x other deep sea habitats
Low diversity - endemic fauna
Unstable, short lived
Chemosynthesis (not photosynthesis)
Highly toxic - sulfide, metals

Question 13

First expedition to find “thermal anomaly”

Answer 13

Deep-Tow vehicle

Question 14

Expedition that found hot springs on Galapagos Rift

Answer 14

Alvin expedition 1977

Question 15

First biological expedition on Galapagos Rift

Answer 15

Alvin (?) 1979

Question 16

Vents are _______-driven environments

Answer 16

physically - driven environments

Originate and die due to geological events

Question 17

What properties determine the species found at hydrothermal vents?

Answer 17

Species available
Water chemistry and temp
Species interactions (facilitation and inhibition)

Question 18

Divergent boundaries between plates

Answer 18

Ridge crests (most with bare rock)

Question 19

Convergent boundaries between plates

Answer 19

Subduction zones (trenches)

Question 20

Transform boundaries between plates

Answer 20

fracture zones