lecture 18: transparency & bioluminescence Flashcards
Options for avoiding search/detection phase of visual predators?
- Mirrored surfaces
- like fish scales
- Counter shading/illumination
- Transparency
***these things minimize contrast
How is transparency achieved?
- Eliminate pigments
- problems: eyes, food in gut, sunscreens - Thinness
- Surface micro-bumps
- blurs the outline of organism - Ultrastructural specializations
how to fix problems w eyes, food in gut, and sunscreens?
fibre optic eyes
Mirrored guts or red-pigmented guts
carotenoids in copepods (pigmentation) to protect from UV
Bioluminescence
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
Bioluminescence in the Ocean
- 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
Bioluminescence - Functions (4)
1) communication - sexual signals
2) attraction of prey - lures
3) illumination of prey - bioluminescent flashlights
4) defense from predators
bioluminescent functions/tactics
1) startle
2) counter illumination
- photophores in cephalopods
3) misdirection: smoke screen
- shrimp spews bioluminescent cloud
4) distractive body parts
- anglar fish
Burglar alarm hypothesis
- 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