lecture 18: transparency & bioluminescence Flashcards

1
Q

Options for avoiding search/detection phase of visual predators?

A
  • Mirrored surfaces
  • like fish scales
  • Counter shading/illumination
  • Transparency

***these things minimize contrast

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2
Q

How is transparency achieved?

A
  1. Eliminate pigments
    - problems: eyes, food in gut, sunscreens
  2. Thinness
  3. Surface micro-bumps
    - blurs the outline of organism
  4. Ultrastructural specializations
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3
Q

how to fix problems w eyes, food in gut, and sunscreens?

A

fibre optic eyes

Mirrored guts or red-pigmented guts

carotenoids in copepods (pigmentation) to protect from UV

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4
Q

Bioluminescence

A

Definition:
A chemical reaction within an organism that emits light

Mechanism:
Luciferin – substrate that emits light when oxidized Luciferase – enzyme that catalysis the reaction
OR
Photoprotein
- molecule with binding sites for luciferin & O2
- co-factor (usually Ca++) causes conformational
change of photoprotein allowing interaction between luciferin and O2)

***reaction needs oxygen and a co-factor which allows them to bind

  • luciferase acts as catalyst
  • oxygen combines with luciferin
  • oxidized luciferin becomes inactive oxyluciferin
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5
Q

Bioluminescence in the Ocean

A
  • 80% of pelagic animals in ocean emit light
  • Bioluminescence is major source of light for much of ocean (mesopelagic zone)
  • Mostly blue light emission (470nm)
  • Evolved minimum of 40X
  • Most bioluminescent organisms do NOT get their light from symbiosis with bioluminescent bacteria
  • Original evolutionary origin? Antioxidant hypothesis
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6
Q

Bioluminescence - Functions (4)

A

1) communication - sexual signals

2) attraction of prey - lures

3) illumination of prey - bioluminescent flashlights

4) defense from predators

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7
Q

bioluminescent functions/tactics

A

1) startle

2) counter illumination
- photophores in cephalopods

3) misdirection: smoke screen
- shrimp spews bioluminescent cloud

4) distractive body parts
- anglar fish

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8
Q

Burglar alarm hypothesis

A
  • Organism #1 is preyed upon by organism #2, which in turn is preyed upon by organism #3
  • Organism #1 emits light when attacked by organism #2
  • Light attracts organism #3, which is a predator of organism #2
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