Untitled

ABCS 403: Environmental Physiology

Bioluminescence

Definition
  • Bioluminescence refers to the production and emission of light by living organisms.
  • It is a type of chemiluminescence, characterized by light generated through a chemical reaction.
Chemical Process
  • The fundamental reaction in bioluminescence involves:
    • Luciferin (the light-emitting molecule)
    • Oxygen (reactant)
    • Luciferase (an enzyme acts as a catalyst in the reaction)
    • Some species (e.g., jellyfish) utilize photoproteins such as aequorin as a catalyst instead of luciferase.
    • The presence of cofactors, such as magnesium (Mg) or calcium (Ca), and sometimes ATP may be involved in the bioluminescent reaction.
Characteristics of Luciferin and Luciferase
  • Luciferins are generally conserved across species, with minimal variation.
    • Example: Coelenterazine is present in 9 to 11 different animal phyla.
    • Some animals acquire luciferin through their diet.
  • Luciferases exhibit significant variation between different species.
    • Despite differences, luciferin, luciferase, and oxygen are prevalent among all bioluminescent organisms.
Biochemical Reaction
  • The bioluminescent reaction can be summarized as follows:
    • ext{Luciferin} + O_2
      ightarrow ext{Oxyluciferin} + ext{light energy} + (CO_2 + PP ext{ (pyrophosphate) or AMP as waste products})

Bioluminescence: Distribution

General Distribution
  • Bioluminescent organisms can be found widely across different environments:
    • Marine Environments: Includes both vertebrates (e.g., fish) and invertebrates, some fungi, and bacteria.
    • Terrestrial Environments: Includes fungi, bacteria, and arthropods, notably fireflies.
  • A symbiotic association with bacteria occurs with some animals (e.g., bacteria from the genus Vibrio).
Statistical Insights
  • In marine coastal habitats, approximately 3% of organisms exhibit bioluminescence.
  • In some pelagic habitats, bioluminescent organisms can make up to 76% of certain deep-sea taxa.
Taxonomic Diversity
  • Organisms producing light in the marine ecosystem include:
    • Vertebrates (e.g., ray-finned fish)
    • Arrow Worms
    • Molluscs (e.g., cephalopods)
    • Crustaceans
    • Cnidarians (e.g., jellyfish, corals)
    • Radiolarians
    • Protozoans (e.g., dinoflagellates)
  • Note: Some organisms do not synthesize luciferin.

Bioluminescence: Colors of Light

  • The majority of light emitted in the marine environment falls within the blue and green spectra.
  • Certain fish species can produce red, infrared, and even yellow light.

Bioluminescence: Uses

Various Functionalities
  • Counterillumination camouflage: Helps organisms blend into their surroundings.
  • Attraction: Lures prey using bioluminescent signals.
  • Defense Mechanisms:
    • Startles prey
    • Provides counterillumination camouflage
    • Creates smoke screens or misdirection
    • Distracts with body parts or serves as a burglar alarm
    • Sacrificial tags or warning coloration to indicate unpalatability or toxicity to predators.
  • Communication: Enables light-based signaling among zooids of the same organism.
  • Mimicry: Mimics other species to attract prey.
  • Illumination: Provides light in dark environments.
Biotechnological Applications
  • Bioluminescence is utilized in various fields:
    • Biology and medicine for imaging techniques.
    • Utilization as reporter genes in genetic studies.
    • Light production applications.

Semiochemicals in Animal Survival and Interaction

Overview
  • For an organism to thrive in its environment, effective communication is essential.
  • Organisms must be able to perceive environmental stimuli as well as send messages to other organisms.
  • Semiochemicals are organic compounds used to convey information between animals and their surroundings.
  • They assist organisms in countering abiotic (non-living) and biotic (living) stressors.
Functions of Semiochemicals
  • Predominantly utilized by insects for:
    • Locating mates
    • Finding food sources
    • Identifying hosts
    • Avoiding natural enemies
    • Steering clear of competitors
    • Overcoming host defense mechanisms
Classification of Semiochemicals
  • Semiochemicals can be divided into:
    • Pheromones (intraspecific semiochemicals): Affect individuals of the same species.
    • Allelochemicals (interspecific semiochemicals): Influence individuals of different species.

Types of Pheromones and Their Effects

Pheromones
  • Defined as volatile chemicals secreted into the environment by one species that affect the behavior or physiology of another member of the same species.
Allelochemicals
  • Defined as volatile substances emitted by one species that influence the behavior or physiology of another species.
Pheromone Types
  • Primer Pheromones: Induce physiological changes without immediate behavioral alterations.
    • Example: Affect development, reproduction, and learning.
  • Releaser Pheromones: Cause immediate behavioral responses.
    • Example: Used in alarm signaling, trail marking, aggregation, sexual behavior, territorial defense, and kin/homing recognition.
Classification of Releaser Pheromones
  • Releaser pheromones can be further categorized into:
    • Trail Pheromones: Blend of metabolic byproducts used for recruitment and marking pathways.
    • Alarm Pheromones: Indicate danger (e.g., mouse alarm pheromone 2-sec-butyl-4,5-dihydrothiazole (SBT)).
    • Aggregation Pheromones: Facilitate clustering (e.g., those in termites).
    • Sex Pheromones: Stimulate sexual behavior (e.g., male-specific secretions in mammals that enhance female attraction).
Specific Examples of Pheromones
  • Examples include:
    • Trail Pheromones: Found in the poison glands of Myrmica ants
    • Aggregation Pheromones: Pheromone combinations in Reticulitermes speratus (2-phenylundecane and cuticular hydrocarbons).
    • Sex Pheromones: Species-specific attractants in mice, such as male-specific exocrine gland-secreting peptide 1 (ESP1), which promotes female sexual behaviors.
Additional Categories of Allelochemicals
  • Kairomones: Benefit receiving organisms at the emitter's expense (e.g., lactic acid in human sweat attracts mosquitoes).
  • Allomones: Advantageous to the emitter without affecting the receiver (e.g., alkylpyrazine protecting Metriorrhynchus beetles).
  • Synomones: Beneficial to both producer and receiver (e.g., terpenes from damaged pines).
  • Apneumones: Emanate from non-living sources and benefit receivers (e.g., hexanal from rabbit stools attracting sandfly females for oviposition).