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Bioluminescence: Functions & Control Mechanisms (p. 94-95 in Syllabus)
Reading: There was an 8-page handout provided in lecture on Friday, May 12. It is an essay on the "Ecology of Bioluminescence" written by Dr. Case, et al. 1994.
Please see the Bioluminescence Web Page for additional information: http://lifesci.ucsb.edu/~biolum.
Introduction
- Importance of link between visual (sensory) system and Bioluminescence (BL) (effector) system
- Multiple evolutionary origins of BL, much fewer in vision (maybe only one??)
- Electroreception is both a sensory system (ability to sense electrical fields) and an effector (ability to emit active electrical pulses)
- Vision is the sensory end to BL (the effector)
- Therefore vision is a key component to understanding the uses and importance of BL in evolution
- Compare with electroreception (Darwin and co-evolution of different groups of electric fish)
- Ex. of a function of BL where vision is critical…the black dragonfish…”light to spy by”
The following example illustrates one function of BL and the importance of vision in BL systems.
Black Dragonfish: light to spy by 
- The colors of the spectrum that humans can see are mediated by three different types of cones each with a cone opsin (vis. pigment) that has a different wavelength sensitivity spectrum : Red, Green, and Blue
- Each of these three spectra overlap so we can see all colors of the rainbow or the portion of the EM spectrum called visible light, wavelength = 400 nm - 700 nm
- Not all animals possess the same spectral sensitivity: they have different visual pigments
- Deep Ocean, only light = BL, which is blue, therefore most fish have only blue-sensitive visual pigments to see with
- The black dragonfish have a BL photophore below their eyes which emits deep red light, but HOW DO THEY SEE IT IF THEY ONLY HAVE BLUE-SENSITIVE VISUAL PIGMENT???
- The answer is on the bioluminescence web page.
Function of BL & Imp. of Vision--ex. #2: the fireflies
- Fireflies use BL to communicate (in addition to a couple of other things), primarily to find a mate
- This is an example of intraspecies signaling
- Have huge eyes relative to body size, indicating importance of vision in survival (to see BL)
- Two types of signaling
- one-to-one signaling (male to female) importance of frequency code!! (these species live on the East coast of US)
- mass signaling (lots of males signal together to far off females) importance of rhythmicity and synchrony! (these species live in Malaysia)
Video examples of firefly behavior
Watch lab video
- male flying, watching for a response to his flashing
- notice how he orients to the “fake” flash
- think of all that is being integrated in his little brain in order to mediate this simple behavior
Watch Nature’s Neons: Synchronizing fireflies
- how they synchronize: anticipatory synchronization, no leader
- why they synchronize: long-distance communication
Another function of BL & its control
- Ostracods: tiny marine crustaceans (see video)
- Use BL to startle predators (and/or as a decoy to avoid predation) AND to communcate within species to find a mate (like fireflies)
- Control mechanism: two components of reaction: luciferin and luciferase are stored separately inside organism. Each is extruded and mixed in the seawater when light emission is desired.
- Unlike the importance of ions in control of luminescence in other systems
Control of BL at the ionic level (direct control of the BL reaction)
See web site for a review of BL chemistry
- Importance of Ca+2 in many BL systems
- Importance of Ca+2 in neural mechanism in general
- Other: H+, ATP, O2
- How might an organism mediate these ionic fluxes? Neural control
Sensory Input that can trigger BL
- Mechanical stimulation
- Chemical Stimulation
- Photic Stimulation
- Electrical Stimulation (only in lab for experimental purposes)
- examples: See video
- THINK ABOUT HIGHER LEVEL INTEGRATION THAT THE ORGANISM IS DOING, SENSORY INPUT, THRESHOLDS, EFFECTOR (BL) CONTROL
For a review of the major uses of BL (the one's that are sort of known anyway) see Edie Widder's BL Web site.
Go to the "Why they make light" section.
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