BIOLOGY 457/657PHYSIOLOGY 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 Organs Bacterial Organs

Widely distributed In only a few fish & squid species

May be very numerous (>1000) Usually only 1 - 2 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) PhotocytesBacteria (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 COUNTERILLUMINATIONExample: 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