bioluminescence

*Bioluminescence in Marine Organisms*

*What is Bioluminescence?*

Bioluminescence, or "living light," is the ability of marine organisms to produce light.

*Light-Producing Creatures:*

1. Dinoflagellates

2. Radiolarians

3. Hydroids

4. Jellyfishes

5. Alcyonarians

6. Ctenophores

7. Bryozoans

8. Polychaetes

9. Brittle stars

10. Crustaceans

11. Gastropods

12. Bivalves

13. Cephalopods

14. Prochordates

15. Fishes

*Habitat of Light-Producing Organisms:*

1. Found in all marine communities

2. From surface to abyssal depths

3. More common in tropical waters than higher latitudes

*Nature of Cold Light:*

1. Minimal heat loss

2. Different from sunlight

3. Free from UV and IR rays

4. Colors produced:

    - Blue (predominant)

    - Yellow

    - Green

*Types of Bioluminescence:*

1. Intracellular (within cells)

2. Extracellular (luminous secretions discharged into water)

3. Bacterial bioluminescence (luminous bacteria in tissues)

*Functions of Bioluminescence:*

1. Attract prey

2. Defense mechanism

3. Communication

4. Camouflage

5. Lure mates

_Luminescent Organs_

*Types:*

1. Unicellular: Single cells producing light.

2. Multicellular: Groups of cells forming light-producing glands.

*Distribution:*

1. Throughout the body (e.g., Emplectonema kandai).

2. Restricted to specific areas (e.g., Chaetopterus variopedatus).

*Examples:*

*Nemertean worm (Emplectonema kandai)*:	Photogenic cells distributed throughout the body.
*Chaetopterus variopedatus	*: Luminous secretion from glands in aliform notopodia
Odontosyllis*	Glands at the base of parapodia
Ostracod Cypridina	Photophores with luciferin and luciferase granules.
. *Mollusks*:	- *Phyllirrhoe bucephala*: Luminescent organs scattered throughout the body.     - *Photus dactylus*: Luminous secretion from three areas (mantle edge, inhalant siphon, and retractor muscle).
Deep-water squid (Heteroteuthis dispar)*:	* Luminous gland with reservoir and two openings

*Structure:*

1. Photophores: Specialized light-producing cells.

2. Luciferin and luciferase granules: Produce light when mixed.

3. Reservoirs: Store luminous material.

4. Openings: Release luminous secretion into the environment.

*Function:*

           Bioluminescence: Produce light for communication, defense, or attraction.

_Intracellular Luminescent Organs_

_Definition:_ Light-producing structures within cells.

Nocitluca_:	_ Granules in cell periphery produce light.
_Hydromedusae	Luminous cells grouped beneath endoderm of marginal canals.
Sea-pens	Luminous cells in endoderm of tentacles.
Ctenophores	Glandular structures within radial canals
Crustaceans	Shrimps_ (Caridean and Penaeid): Photophores on appendages.     - _Euphausids_ (Meganyctiphanes): Photophores with lenses and corneal layer.
Deep-sea squids_ (Leachia	Ocular photophores with lenses, corneal layer, and glandular mass.
_Deep-sea teleosts	Myctophum_       _Argyropelecus_       _Stomias_       _Photostomias
Astromesthes	Numerous photophores along body.

_Structure:_

1. Granules: Contain luciferin and luciferase.

2. Luminous cells: Grouped or scattered.

3. Photophores: Specialized light-producing organs.

4. Lenses: Focus light.

5. Corneal layer: Thickened layer enhancing light transmission.

6. Reflector: Connective tissue surrounding glandular mass

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