Chemical ecology of Chemical ecology of tropical algae:tropical algae:tropical algae:tropical algae:

Part IIPart II

Bernardo A.P. da Gama

1

Universidade Federal Fluminense

Niterói – Rio de Janeiro ‐ Brazil

1

OutlineOutline

• 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

2

• Defenses against herbivores

• Defenses against epibiontsl 2g p

caulerpenyne

PartPart IIII

• 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

3

• Defenses against herbivores

• Defenses against epibiontsl 3g p

caulerpenyne

Resource allocation modelsResource allocation models

Are defenses costly to algae?

• Optimal Defense Model 

• Carbon‐Nutrient Balance Model

• Growth‐Differentiation Balance Model

• Environmental Stress Model

Ob D i h i ill

4

Obs.: During the experiments we will test resource 

allocation theory 4

Optimal Defense ModelOptimal Defense Model

• Defenses are costly, thus algae allocate h f h h ll l blthem to parts of the thallus more valuable or more susceptible to herbivores

• Could explain intraspecific variation, interspecific variation and biogeographic variation in chemical defenses

• Well‐accepted theory with some validation

5

p y

5

Optimal Defense Model Optimal Defense Model 

• Demand‐based model focusing on the l ’ d f d f d hplant’s need for defenses and on the 

evolutionary pros & cons of defense ll iallocation per se

• Defense Induction models are a natural derivation from the ODM

66

CarbonCarbon‐‐Nutrient Balance ModelNutrient Balance Model

• Resource‐based model, stating that production of defenses is determined by relative availability of C and nutrients

h i i i h li h• When nutrients are scarce, restraining growth, a light increase would result in excess carbon that could then be used to C‐based defenses (e.g. polyphenolics)used to C based defenses (e.g. polyphenolics)

• A few temperate species seem to conform with this model, but the majority does not

7

• Secondary metabolites seen as “waste products”

7

GrowthGrowth‐‐Differentiation Balance ModelDifferentiation Balance Model

• Acquired resources are allocated among the processes of growth and differentiationthe processes of growth and differentiation

• Including cell specialization and chemical d f ddefense production

• Parts of the thallus with active growth would thus be less defended than old, differentiated parts

8

• Pattern inverse to the ODM

• Few experimental tests of this model 8Few experimental tests of this model

ESM ESM –– Environmental Stress ModelEnvironmental Stress Model

• Suggests that environmental stress can reduce growth, affecting the resource supply and also the production of chemical defenses

E i l ll l i h i• Environmental stresses usually result in changes in nutritional value or in a reduction of chemical defense concentrations, such as dictyols in D. ciliolataconcentrations, such as dictyols in D. ciliolata

H

OOH

HHOC

9Dictyota ciliolata 4β‐hidroxidictyodial A

9Renaud et al. (1990) Oecologia                                                  Cronin & Hay (1996) Ecology

GDBHGDBHResourceResource acquisionacquision

CNBMCNBM

10

ESTEST GDBMGDBMODMODM

10

DefenseDefenseMaintenanceMaintenance AbioticAbiotic stressstress

HerbivoryHerbivory: a peculiar form of predation: a peculiar form of predation

• Herbivores feed on the whole plant or on just part of the thallus

• When they feed on part of the thallus, they play a role similar to that of parasitesp y p

• Phyletic diversity of marine herbivores is enormous when compared to terrestrial

11

enormous when compared to terrestrial

11

StrategiesStrategies to to dealdeal withwith herbivoryherbivory

Herbivore attack

susceptible resistant

12

tolerate escape

defend 12

StrategiesStrategies to to dealdeal withwith herbivoryherbivory

tolerance

spacespace

timeHalimeda sp

escape

Ulva sp.

association

Halimeda sp.

13defense Sargassum sp. Hypnea sp. 13g p

ChemicalChemical defensesdefenses againstagainst herbivoresherbivores

• Structural defenses

• Associational defenses

• Nutritional defenses

• Chemical defenses

1414

ChemicalChemical defensesdefenses againstagainst herbivoresherbivores

• nutritional

• associationalMithrax sculptus

• structural

• mineral

Neogoniolithon sp.

mineral

• morphological

15

• chemical Halimeda sp.

according to Paul et al. (2001) In: Mar. Chem. Ecol. 15according to Paul et al. (2001) In: Mar. Chem. Ecol.

DiversityDiversity ofof marine marine herbivoresherbivores

Snail - MolluscaPolychaete - AnnelidaFlatworm - Platyhelminthes

16sea-urchin - Echinodermata Amphipod - Crustacea Crab - Crustacea 16sea urchin Echinodermata Amphipod Crustacea Crab Crustacea

DiversityDiversity ofof marine marine herbivoresherbivores

Fish - ChordataSea turtles - Reptilia

17Manatee Mammalia Phycologist Hominidae 17Manatee - Mammalia Phycologist - Hominidae

TwoTwo typestypes ofof herbivoresherbivores......

• Small mobility herbivores, relativelySmall mobility herbivores, relatively sedentary, that feed and live on the plant:mesoherbivores (worms,plant: mesoherbivores (worms, molluscs, amphipods)

• Larger mobile herbivores are• Larger, mobile herbivores are   called macroherbivores              (fish & sea urchins)

18

(fish & sea urchins)

18

......andand thethe pressurepressure theythey exertexert

• Mobile herbivores are generally diversified and extremely generalistand extremely generalist 

• Due to this diffuse herbivory pressure, natural l d f d fselection tends to favor defenses against a 

wide spectrum of herbivores

• This is likely the reason why coral reef algae employ combinations of chemical, structural 

19

and morphological defenses

Hay (1992) In: Ecol. Roles Mar. Nat. Prod. 19y ( )

MesoherbivoresMesoherbivores

• Smaller, lower‐mobility herbivores are generally subject to higher predation rates

• Chemical defenses that deter fish and sea urchins generally have no effect against mesoherbivores

• “Space free from enemies” selected for chemical d f i l h h h j i f idefense resistance, although the majority of marine mesoherbivores did not become specialist

20Hay (1992) In: Ecol. Roles Mar. Nat. Prod. 20ay ( 99 ) co o es a at od

HerbivoreHerbivore feedingfeeding specializationspecialization

Caribbean reef fish Ascoglossan molluscs

cies

100

% o

f spe

50

%

1 2 3 4 5 6 7 8 9 10 >101 2 3 4 5 6 7 8 9 10 >10 1 2 3 4 5 6 7 8 9 >10

21Hay (1992) In: Ecol Roles Mar Nat Prod

Number of algal families consumed

21Hay (1992) In: Ecol. Roles Mar. Nat. Prod.

Mesoherbivore life historyPlanktonic dispersion

Pelagic larvaeCue detection and Ca 80% of all marinesettlement

Ca. 80% of all marine organisms (> 100 thousand

spp described amongst algae, invertebrates &

vertebrates) have a two-vertebrates) have a two-phase life history with

planktonic dispersion forms

22Benthic 22Benthic adults

SpecializationSpecialization in marine in marine herbivoresherbivores

23

Eggcases of two different species of gastropods laid on thalli of the chemically defended brown alga Stypopodium zonale

23

Why is the world green?

• HSS hypothesis or Green World• Two possibilities:

• Top‐down control: herbivores are limited by consumers; plants escape due to the fact thatconsumers; plants escape due to the fact that herbivore populations are small

• Bottom‐up control: plant defenses, including chemical defenses, reduce the ability of herbivores to use plants as a resource

24Hairston, Smith & Slobodkin (1960) Am. Nat.

24

Why is the world green?

• There is evidence to support both:• Top‐down control: sea otter hunting in northern Pacific led to destruction of kelp beds due to the absence of sea urchin predatorsp

• Bottom‐up control: coral reefs have a high diversity of chemically defended macroalgae; the only erect 

l th t i t i b “i k ”macroalgae that persist in barren or “isoyake” areas are chemically or structurally defended

25

Paul (1992) In: Ecol. Roles Mar. Nat. Prod.

Kurata et al. (1998) Phytochemistry25

2626

Behavioral sequestration of algal chemical defenses

• Decorator crabs from 3 sites above North Carolina do fl t t dicamuflate so as to disappear 

• On the other hand, specimens from 3 southern, warmer sites cover exclusivelly with the chemically defended Dictyota menstrualisdefended Dictyota menstrualis

• In winter, D. menstrualis disappears and crabs from these sites then shift to the toxic sponge Hymeniacidon

Libinia dubia

27Stachowicz & Hay (2000) Am. Nat. 

sites then shift to the toxic sponge Hymeniacidon heliophila

27

SpecialistSpecialist herbivoresherbivores thatthat do do notnotsequestersequester chemicalchemical defensesdefensesqq

• The Caribbean crab Thersandrus compressus is foundonly in Avrainvillea longicaulis, the only alga this speciesfeeds on during feeding trials

• The crab is readily eaten by the wrasse Thalassoma• The crab is readily eaten by the wrasse Thalassomabifasciatum when offered without the host algae

© ww

ww.recif-franc

28avrainvilleol

Avrainvillea spT. bifasciatum

Hay et al (1990) Limnol Oceanogr

ce.com

28Hay et al. (1990) Limnol Oceanogr

SpecialistSpecialist herbivoresherbivores thatthat do do notnotsequestersequester chemicalchemical defensesdefenses

• The Great Barrier reef crab Caphyra rotundifrons livesd f d l i th h i ll d f d d l

qq

and feeds only in the chemically defended green alga Chlorodesmis fastigiata

• While reef fishes are deterred by chlorodesmin thisWhile reef fishes are deterred by chlorodesmin, thiscompound stimulates the consumption by the crab

29

chlorodesmin

C. rotundifrons em Chlorodesmis fastigiata Hay et al (1989) Oecologia 29Hay et al. (1989) Oecologia

SpecialistSpecialist herbivoresherbivores thatthat do do notnotsequestersequester chemicalchemical defensesdefenses

med

med

qq

rabs

rabs

cons

umco

nsum

eate

nea

ten

((mg

mg))

Num

ber

Num

ber

ofofcc

Mas

sM

ass NN

30

Chlorodesmin concentration (%) Chlorodesmin concentration (%) In the red seaweed In the red seaweed AcanthophoraAcanthophora

Hay et al. (1989) Oecologia 30Hay et al. (1989) Oecologia

SpecialistSpecialist herbivoresherbivores thatthat do do notnotsequestersequester chemicalchemical defensesdefensesqq

• The amphipod Pseudamphitoides incurvaria lives in a mobile bivalve domicile built from the chemicallymobile bivalve domicile built from the chemically defended Dictyota bartayresii

• The algal compound that causes fish rejection is used as g p ja chemical cue to build the domicile by the amphipod

31pachydictyol A

D. bartayresii Hay et al. (1990) Ecology 31ba tay es Hay et al. (1990) Ecology

SpecialistSpecialist herbivoresherbivores thatthat do do notnotsequestersequester chemicalchemical defensesdefenses

• Amphipods removed from their domiciles or in domiciles built using Ulva sp are readily consumed

qq

%)

%)

eses

domiciles built using Ulva sp. are readily consumed

cons

umed

cons

umed

(%(%

ldin

gld

ing

dom

icile

dom

icile

Am

phip

ods

Am

phip

ods

divi

dual

sdi

vidu

als

buil

buil

32PachydictyolPachydictyol A A concentrationconcentration (%) (%)

Ind

Ind

“behavioral sequester of chemical defenses” 32

Hay et al. (1990) Ecology

behavioral sequester of chemical defenses

SpecialistSpecialist herbivoresherbivores thatthat sequestersequesterchemicalchemical defensesdefenses

• The ascoglossan Elysia halimedae occurs exclusively in l f th H li d d f d f bl thalgae of the genus Halimeda, and feeds preferably on themore chemically defended portions of the thalli

• Halimedatrial composes up to 7% of the dry mass of theHalimedatrial composes up to 7% of the dry mass of themollusc

• The chemical defense is transferred to the eggs of the mollusc, that thus gain protection against predators

33Elysia in Halimeda sp.Paul & Van Alstyne (1989) J Exp Mar Biol Ecol 33

SpecialistSpecialist herbivoresherbivores thatthat sequestersequesterchemicalchemical defensesdefenses

• The ascoglossan C. ocellifera is one of the mostinteresting cases of feeding specialization: avrainvilleol is

CH2OHCH2OH

interesting cases of feeding specialization: avrainvilleol is sequestered from its only feed item, as well as chloroplasts

OH

Br

OHBrOH

OH

Br

OHBrOH

• The chloroplasts remain functional in the 

avrainvilleolavrainvilleolmolluscan cells for up to 3 months

34Costasiella oclellifera in Avrainvillea longicaulisHay et al. (1990) Limnol Oceanogr

34

SpecialistSpecialist herbivoresherbivores thatthat produceproduce theirtheirownown chemicalchemical defensesdefenses

• The mollusc Tridachia crispata lives and feeds on

chemically defended seaweeds, but synthesizes his

own secondary metabolitesown secondary metabolites

• Compounds effectively

deter predators

35Tridachia crispata

Hay & Fenical (1996) Oceanography 35

NatureNature ofof chemicalchemical defensesdefensesagainstagainst herbivoresherbivores

Laurencia obtusa

gg

Dictyota cervicornis

Constitutive defenses

Caulerpa taxifolia Halimeda tunaActivated defenses

36Pereira et al. (2002, 2003) Braz. J. Biol.

Jung & Pohnert (2001) Tetrahedron 36Paul & Van Alstyne (1992) J. Exp. Mar. Biol. Ecol.

InducibleInducible DefenseDefense ModelModel

( )s

(+)benefit

constitutive defensest fit

ness

induced defensesconstitutive defenses

Pla

n

(-)no defenses

37

low highHerbivory intensity

( )cost

Karban et al. (1999)37

DefenseDefense inductioninduction

Small mobility herbivores attack(e.g. amphipods)

High chemicaldefense level

ResistanceResistance totofuture future atacksatacks

38Low defense level

38

Induction of defenses against herbivores

• Few tropical studies

• F 9 t i l d bj t t• From 9 tropical seaweeds were subject to induction by amphipods, 8 of which showed some degree of inductiondegree of induction

• First case of defense induction among red algae

39Elasmopus brasiliensis

Weidner et al (2004)Mar Ecol Prog SerP l di ll ill 39Weidner et al. (2004) Mar. Ecol. Prog. Ser.Pterocladiella capillacea

InteractionsInteractions amongamong algaealgae, , epibiontsepibiontsandand herbivoresherbivoresandand herbivoresherbivores

• Epibiosis may protect (“protective coating”) or( protective coating ) or attract consumers to the alga (“shared doom”)

Photo

by

• In the majority of cases, it seems to be harmful to algae, increasing the nutritional 

Steve P

atogvalue

• Epibionts in C. seminervis i b th ti The red seaweed Cryptonemia seminervis

on

40

increase both consumption and chemical defenses against fouling

ypfrom Bocas del Toro, Panamá

Da Gama et al (2008) Biofouling 40Da Gama et al. (2008) Biofouling

DefensesDefenses againstagainst epibiontsepibionts

• Marine natural products have been seen as the most promising alternatives to toxic antifouling f l tiformulations

• A number of extracts and isolated d h b d dcompounds have been tested and 

patented as new antifoulantsElatol from Laurencia obtusa

41

• Inestimable economic, ecological and social importance

Elatol from Laurencia obtusa

41

DefensesDefenses againstagainst epibiontsepibionts• Possibly, antifouling defenses were developed in response to the disadvantages caused byin response to the disadvantages caused by epibiosis in algae

• However little is known about their ecological role in• However, little is known about their ecological role in nature

• Or the forces that have driven the evolution of• Or the forces that have driven the evolution of antifouling chemical defenses in marine organisms

• Absolute lack of wide‐scale antifouling studies with

42

Absolute lack of wide scale antifouling studies with standardized methodology

42

DefensesDefenses againstagainst epibiontsepibionts ‐‐methodsmethods

• LaboratoryLaboratory

• Field

43Da Gama et al. (2003) Biofouling 19: 161-169 43

4444

44

4545

45

Jamaica (18oN)

F N h (3 S)

StudyStudysitessitesStudyStudysitessites F. Noronha (3oS)

Rocas (5oS)Abrolhos

sitessitessitessites

(17oS)Marataizes

(19oS)Anchieta (19oS)Angra(20oS)It i (22 S)

A. Cabo(23oS

Buzios(23oSItaipu(22oS)

46Couves (24oS)

P i B (24oS)

C. Frio (23oS)

46

46

Praia Branca (24oS)Praia Brava (24oS)

Praia do Poa (27oS)

Green Green algaealgaegg

4747

47AntifoulingAntifouling activityactivity Da Gama et al. (2008) Bot Mar

Brown Brown algaealgae

4848

48AntifoulingAntifouling activityactivity Da Gama et al. (2008) Bot Mar

Red algaeRed algaeRedRed algaealgaegg

4949

49

AntifoulingAntifouling activityactivity Da Gama et al. (2008) Bot Mar

Are there latitudinal patterns?p

5050

50

Are Are therethere phylogeneticphylogenetic trendstrends??

Chlorophyta Phaeophyta Rhodophyta

51Strong ModerateInactive Da Gama et al. (2008) Bot Mar

Antifouling activity

51Inactive ( )

Brown Brown algaealgae & & settlementsettlement inducersinducers

Stypopodium zonale

Soares et al. (2008) Mar Biotechnol 10

5252

epitaondiol

Brown Brown algaealgae & & settlementsettlement inducersinducers

Large scale field experiment using Stypopodiumzonale crude extracts

5353

GameteGamete chemotaxischemotaxis

• First description of chemical attraction of gametes l b k t 1854 ith th b damong algae goes back to 1854, with the brown seaweed 

Fucus vesiculosus

• Today we know that this pheromone‐mediated• Today we know that this pheromone mediated fertilization process is common in the large majority of brown seaweeds along the world (ca. 100 species)

Photo

byS

54

Thuret (1854) Ann Sci Nat Bot

Amsler & Iken (2001) In: Mar. Chem. Ecol.

Steve Paton 54Amsler & Iken (2001) In: Mar. Chem. Ecol.

Life cycle of a brown  seaweed 

• After release from female  sporophytesporophyte

R!R!

gametangia• Haploid female gametes 

release pheromones that  zygotezygotesettlementsettlement

guide male gametes toward the source

• Then a diploid zygote f l

gametesgametes ����

forms, settles and turns into a sporophyte

• The vegetative h h f

gametangiagametangia

55

sporophytes then form the meiospores that originate the gametophytic plants

gametophytegametophyte

����55gametophytic plants ����

TheThe naturenature ofof sexual sexual pheromonespheromones

• Chemoattactors of male gametes include 11 different C11 h d b d C d 50 t i fhydrocarbons and one C8, and ca. 50 stereoisomers of these compounds

• All are volatile with action ranges of up to 1000 µm• All are volatile, with action ranges of up to 1000 µm

• They always involve the attraction of male gametes to female gametesg

• Structural pattern relatively uniform suggests a common biosynthetic nature → fatty acids

56

• Petroleum hydrocarbons are so similar to pheromones that pollution is leading to local extinction of brown algae! 56algae!

TheThe naturenature ofof sexual sexual pheromonespheromones

Ectocarpus kelps

Perithalia bouquetbouquet

Cutleria

FucusHormosira

Dictyota

5757

EcologicalEcological relevancerelevance ofofsexual sexual pheromonespheromonespp

• It is surprising that pheromones are lipophilic p g p p phydrocarbons → short range

• Competing species can use the same pheromone or minoritary compounds of the bouquet

• The absence of specificity is compensated by immunological barriers at the cell surface

• The role that pheromones play in situ still remains 

58

largely unknown → defense against low mobility herbivores (amphipods)

Hay et al (1998) Chemoecology 58Hay et al. (1998) Chemoecology

Tools in Tools in algal algal ggchemical chemical ecologyecologyecologyecology

Co rtes ofCourtesy of Keri GoodmanGeorgia Institute of Technology

5959

Perspectives in Perspectives in algalalgal chemicalchemical ecologyecology

1. Understand variation in production of chemical defenses in time, space and within‐thallus

2. Discover the mechanisms of production, storage and release of natural productsg p

3. Investigate the community effects of chemical defenses

60

chemical defenses

60

Tubular connexions between the corps en cerise andthe cell wall in Laurencia obtusa

6161Salgado et al. (2008) J Struct Biol

Vesicular Vesicular traffictraffic betweenbetween thethe corpscorps enen cerisecerise andand thethe cellcell wallwallin in LaurenciaLaurencia obtusaobtusa

6262

LysisLysis ofof corpscorps enen cerisecerise andand subsequentsubsequent cellcell deathdeath triggeredtriggeredbyby increasedincreased temperaturetemperature

6363

ModelModel ofof thethe tubular, tubular, membranousmembranous connexionsconnexions andand vesicular vesicular traffictraffic betweenbetweenthethe corpscorps enen cerisecerise andand thethe cellcell wallwall in in LaurenciaLaurencia obtusaobtusa

6464

TheThe truetrue role role ofof natural natural productsproducts

• “...from the functional point of view, natural products

are vocables of the ecological-evolutionary language”Gottlieb, OR (2001) RESEM, Universidade de São Paulo

• Seaweeds are masters of the chemical language and each new researchSeaweeds are masters of the chemical language, and each new research

discovers evidence in favor of new applications: defense against herbivores,

pathogens, gamete attraction, symbiont attraction, allelopathy, antifouling, UV

65

protection, etc. The algal jargon can even be used by specialized herbivores

to communicate with their own predators65

AcknowledgementsAcknowledgements

• Rachel CollinRachel Collin

• Keri Goodman 

C i A k• Craig Aumack

• NSF / PASI 

• STRI

6666

CollaboratorsCollaborators

• Renato C. Pereira – UFF, Brazil 

• Ricardo Coutinho – IEAPM, Brazil

• Gilberto M. Amado Filho – JBRJ, Brazil,

• Leonardo T. Salgado – JBRJ, Brazil

• Martin Wahl IfM Geomar Kiel Germany• Martin Wahl – IfM Geomar, Kiel, Germany

• Markus Molis – Helgoland, Germany

67

• Claire Hellio – Univ. Portsmouth, UK

• All my students, past and present 67y p p

Final Final thoughtthought

What world will we leave for the future generations?

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