BIOLOGY 457/657 PHYSIOLOGY OF MARINE & ESTUARINE ANIMALS March 15, 2004 BIOLUMINESCENCE

BIOLUMINESCENCE: INTRODUCTION Outstanding and widely distributed feature of marine animals; rare in fresh water. “Cold light” in visible spectrum: chemiluminescence Most common in midwater (mesopelagic) animals, but occurs throughout the ocean Has a broad phyletic pattern – see the handout.

LUCIFERIN/LUCIFERASE Luminescence involves the action of the enzyme luciferase on the substrate luciferin. There are many non-homologous varieties of luciferin (see handout) and luciferase.

INTRINSIC vs BACTERIAL LUMINESCENCE Intrinsic OrgansBacterial Organs Widely distributed In only a few fish & squid species May be very numerous (>1000) Usually only per individual Several types can exist together Only 1 type per individual Usually closed off Always open to exterior (or gut) Rarely associated with the gut Often associated with the gut Under nervous or other control Always illuminated (may have a shutter) Genetically expressed Require inoculation & culture

UNITS OF LUMINESCENCE (1)Extracellular luminescence (released) Slimes (e.g. in polychaetes such as Chaetopterus) “Ink” (from deep-water squids) “Spew” (from deep-water shrimp) “Decoys” (from ostracods) (2)Photocytes Bacteria (Photobacterium) reprepsent a “prokaryotic photocyte” Dinoflagellates – Gonyaulax, Noctiluca In many higher eukaryotes: cnidarians, echinoderms, polychaetes, crustaceans, fishes (3) Photophores

PHOTOPHORES Can be highly organized and controlled light-emitting systems. Usually present in animals with complex vision & behavior. Often contain accessory structures: reflectors, pigments, etc

EXAMPLES OF INVERTEBRATE PHOTOPHORES From Hastings & Morin (1991)

PHOTOPHORES OF TELEOST FISHES

BACTERIAL PHOTOPHORES IN FISHES From Hastings & Morin (1991)

SPECTRAL FEATURES OF BIOLUMINESCENCE

SPECTRAL MAXIMA OF BIOLUMINESCENCE

MULTIPLE PHOTOPHORES: Example 1: Aristostomias scintillans & Malacosteus niger Data from Widder et al., 1984

MULTIPLE PHOTOPHORES: Example 2: Abraliopsis Data from Young & Mencher (1980)

ADAPTIVE SIGNIFICANCE OF BIOLUMINESCENCE The functions fall into 3 general biological categories: (1)Predator Avoidance (the major function in the sea) “Startle” stimulation Predator blinding Aposematic luminescence (prey is unpalatable or inedible) Attracting a larger predator (“burglar-alarm” hypothesis) Ventral counterillumination (including Abraliopsis) Decoying or confusing a predator (lures, clouds, “blink-and- run”; see Photoblepharon example later on)

VENTRAL COUNTERILLUMINATION Example: Hatchetfish Argyropelecus aculeatus Images and data from Herring (1977)

ADAPTIVE SIGNIFICANCE OF BIOLUMINESCENCE (continued) (2)Intraspecific Communication Flashes, glows, and displays (e.g. Vargula – an ostracod, Photoblepharon – a fish) (from ImageQuest) Seems to be involved in mate attraction, aggression, species identification. May be at “secret wavelengths” (Aristostomias ??)

ADAPTIVE SIGNIFICANCE OF BIOLUMINESCENCE (continued) (3)Prey Capture Luminescence may be used as a lure (angler fish) May use defensive camouflage to avoid alerting prey Illuminate prey (Aristostomias?) Mimic prey illumination (no known marine examples) Stun or confuse prey Attract prey by phototaxis (Photoblepharon?)

Photoblepharon: “ LIGHT FOR ALL REASONS” Morin et al., 1975