Chemical ecology of tropical algae: Part I

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Chemical ecology of tropical algaePart I

• Bernardo A.P. da Gama
• Universidade Federal Fluminense
• Niterói Rio de Janeiro - Brazil

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Outline

• The tropical marine environment
• What is seaweed chemical ecology?
• What are secondary metabolites?
• How are they biosynthesized?
• Why are they biosynthesized?
• Ecological roles of macroalgal metabolites
• Resource allocation models
• Defenses against herbivores
• Defenses against epibionts

caulerpenyne
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Part I

• The tropical marine environment
• What is seaweed chemical ecology?
• What are secondary metabolites?
• How are they biosynthesized?
• Why are they biosynthesized?
• Ecological roles of macroalgal metabolites
• Resource allocation models
• Defenses against herbivores
• Defenses against epibionts

caulerpenyne
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References

• Few books, majority of knowledge is hot out of
  the press!
• Consequence of the novelty of this expanding field

Ecological roles of marine natural
products Edited by Valerie J. Paul
Springer 2008
CRC Press 2001
Comstock Publishing 1992
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The tropical marine environment

• Conspicuous and diverse coral reefs are NOT the
  only tropical ecosystems!
• Seagrass beds, rocky shores, mangrove forests
  equally important

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The tropical marine environment

• How to define it?
• Latitude between 23o27 N and S
• SST sea surface temperatures more accurate
  indication

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The tropical marine environment

• Consider this
• Macroalgae are restricted to the euphotic zone
• Present boundaries are set by SS isotherms
  (20oC-winter isotherms)
• Presence of hard substrata is a condition for
  most macroalgae
• Present distribution results from migration
  displacement of coastlines along geological times
  (continental drift)

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The tropical marine environment

• Add to this the recent (500 y.a.) human-mediated
  amplification of distributions bioinvasions
• Further human-mediated changes are to be expected
  if global climatic changes really affect global
  oceanic currents!

Sea Surface Temperature, MODIS satellite data,
NASA, GSFC
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What is algal chemical ecology?

• Science that studies any type of ecological
  interaction involving marine algae mediated by
  chemical compounds
• E.g. herbivory, competition, gamete attraction,
  symbiosis, epibiosis, settlement, etc.

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What are secondary metabolites?

• Also called natural products
• Not involved in primary cell functions
• Thus called secondary metabolites
• Specific or mixed biosynthetic pathways
• Many are group- or even species-specific

Please read Faulkner yearly reviews and later
Blunt et al. entitled Marine natural
products In Natural Product Reports
phlorotannins
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How are they biosynthesized?
Maschek Baker (2008)
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Isoprenoids

• Mevalonate-dependent independent

quinones
terpenes
carotenoids
steroids
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Acetogenins
Polyketides
polyphenolics (phlorotannins)
fatty acids
prostaglandins
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Amino acids
alkaloids
peptides
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Shikimate pathway
flavonoids
coumarins
cinnamic acid derivatives (seagrasses)
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Nucleic acids
nucleotid base
modified nucleic acid
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Carbohydrates
sugar
polysaccharide
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Why are they biosynthesized?

• If you discover, please let me know!
• Some claim they are just metabolic waste
  products
• Some are clearly involved in basic,
  non-ecological roles (e.g., phlorotannins)
• Makes no sense to invest in genetic information,
  enzymes and precursors to synthesize them if they
  play no function!
• Chemical communication and warfare

Williams DH (1989) Why are secondary metabolites
(natural products) biosynthesized? J Nat Prod
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Intraspecific molecular interactions
SEXUAL
AUTOTOXINS
ALARM
AUTOINHIBITORS
TRACK / CUE
GROUPING
PHEROMONES
TERRITORIAL
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Interspecific molecular interactions
SYMBIONT LOCALIZATION
KAIROMONES
PREY LOCALIZATION
ALARM / CUE
benefit the receiver of the chemical message
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Interspecific molecular interactions (II)
ATTRACTION
REPELLENT
DEFENSE
ANTIBIOTIC
ALLOMONES
COMPETITION
POISON
benefit the sender of the message
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Energy source
feromones
sexual
UV protection
Consumption
Bacteria Algae Fungi
Invertebrates fish
simbiosis