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Herbivores offenseVasakorn Bullangpoti, Ph.D.Email: [email protected]

Contents

BEHAVIORAL MECHANISM – LEAST AGGRESSIVE Feeding choice Oviposition choice

PHYSIOLOGICAL AND MORPHOLOGICAL TRAITS – sometime aggressive Enzymes Sequestering Host Chemicals Morphological Adaptations Symbionts

Herbivores Manipulate their host- Aggressive Gall and Induced Plant susceptibility Trenching, Mowing, Haying and Gardening Gregarious Feeding

BEHAVIORAL MECHANISM – LEAST AGGRESSIVE

Feeding choice Self-selection of food is likely to be more

important for herbivores that are more mobile and can gain access to varied diets.

When herbivores fail to make appropriate decision, these “mistake” tend to conservative. Such that herbivores reject food that are actually nutritious to them

http://www.treesaregood.org/treecare/insect_disease.aspx


Cannibalism and predation on other herbivores is associated with nutritional benefits and is more likely when plant foods are scarce or less nutritious.

Three Mormon crickets eating a fourth Mormon cricket

Behavioral adaptations S electively in space and time or season

winter moth , feeding on oak leaves early in the season maximized the amount of protein and nutrients availab

le to the moth, while minimizing the amount of tannins produced by the tree

Herbivores can also spatially avoid plant defenses. The piercing mouthparts of species in Hemiptera allow

them to feed around areas of high toxin concentration. Several species of caterpillar feed on maple leaves by "

window feeding" on pieces of leaf and avoiding the tou gh areas, or those with a high lignin concentration.

Similarly, the cotton leaf perforator selectively avoids eating the epidermis and pigment glands of their hosts

, which contain defensive terpenoid aldehydes.

Trichoplusia caterpillars

http://www.infonet-biovision.org/res/res/files/970.400x400.jpeg

http://www.flickr.com/photos/9546698@N07/2148457971/

Behavioral adaptations

Some animals ingest large amoun ts of poisons in their food, but the

n eat clay or other minerals, whic h neutralize the poisons. This beh

avior is known as geophagy.

Behavioral adaptations

Plant defense may explain, in part, why herbiv ores employ different life history strategies.

Monophagous species (animals that eat plants fro m a single genus) must produce specialized enzy

mes to detoxify their food, or develop specialized structures to deal with sequestered chemicals.

Polyphagous species (animals that eat plants fro m many different families), on the other hand, pro

duce more detoxi fying enzymes (specifically MFO ) to deal with a range of plant chemical defenses.


Oviposition choice Many herbivorous insects cannot move much

during the course of their development. According to the prevailing paradigm, mobile ovipositing female assess different host plant species and place their eggs or offspring on those host that result in the highest performance.

More than half of the recent literatures supported this positive correlation between adult oviposition and offspring performance


Oviposition choice The correlation between mean oviposition

preference and survival and growth of larvae averaged across many females in an herbivore population.

Herbivores may select host plants that provide poor growth but good protection from their own natural enemies


Oviposition choice One recent study, the correlation between

adult choice and performance of offspring. The future field studies of the preference-

performance correlation should consider adult performance as distinct from offspring performance.

EX: Dr.Kainoh’s lab

WIND TUNNEL

PHYSIOLOGICAL AND MORPHOLOGICAL TRAITS

– sometime aggressive-

Teeth Structures

Insect mouthparts

The development of insect mouthparts from the primitive chewing mouthparts of a grasshopper in the centre (A), to the lapping type (B) and the siphoning type (C). Legend: a, antennae; c, compound eye; lb, labium; lr, labrum; md, mandibles; mx, maxillae.

Labrum

Mandible

Siphoning Insects

Stylet

Proboscis

Figure female soapberry bugs from Florida in a 100 year period

http://www.fiu.edu/~biology/class_sites/pcb4674/CH2-EVIDENCE-SPRING-2008/CHAPTER2_SPR_2008.HTML

Morphological adaptation

Many other herbivores traits besides mouthparts can be important and offensive.

Bruchid seed beetles, female adjust egg size and probably other traits in response to particular host plant. On host with hard seeds, fitness is maximized

by laying large eggs whereas on hosts with softer seeds, fitness is higher when females lays more, but smaller, eggs (Fox et al, 1997)

PHYSIOLOGICAL AND MORPHOLOGICAL TRAITS – sometime aggressive-

ENZYME

Enzymes

Detoxification enzyme system

Proteinase Inhibitors

Salivary enzymes

Detoxification Enzyme system

XENOBIOTICS

Highly Lipophilic Lipophilic

Excretion

Phase IOxidation, reduction, Hydrolysis)

Phase IIConjugation

Accumulation in fat body

Polar Hydrophilic

Polar

Hydrophilic

XENOBIOTICS


Excretion


Phase IIConjugation


Polar Hydrophilic

Polar

Hydrophilic

Phase I reaction

Includes oxidative, reductive and hydrolytic reactions .

In these type of reactions, a polar group is either introduced or unmasked, so the drugmolecule becomes more water-soluble and can be excreted .

Esterase

A type: arylesterase that are not inhibited by

organophosphate.

B type: alliesterase, carboxylesterase and cholinesterase There are inhibited by

organophosphate due to irreversible phosphorylation of the active serine site

Carboxylesterase mechanism

Paranitrophenylacetate (pNPA) -------> paranitrophenol

0 = C

NH - C

NH - C

O

O

C2H5

0 = C

NH - C

NH - C

O

O

C2H5

OH

Phenobarbitone p- hydroxyphenobarbitone

NO2

OP (OC2H5)2

S

NO2

OP (OC2H5)2

O

Parathion Paraoxon

P450 enzymes

Cytochrome P450 (abbreviated CYP , P450 , infrequently CYP450 ) is a very large and div

erse superfamily of hemoproteins found in all domains of life.

Usually they form part of multicomponent e lectron transfer chains, called P450-

containing systems.

P450 enzymes

One of very important enzyme

http://www.uky.edu/Pharmacy/ps/porter/CPR_partners.gif

P450 enzymes

The most common reaction catalysed by cytochrome P450 is a

monooxygenase reacti on

Phase II reaction

These reactions involve covalent attachment of small polar endogenous molecule such as glucuronic acid, s

- ulfate, or glycine to form water soluble compounds.

This is also known as a conjugation reaction .

The final compounds have a larger molecular weight.

Aryl or alkyl sulfates and sulfamates

PAPS = Adenosine-3'-P-5'-Phosphosulfate

Sulfate conjugation

Mercapturic acid

glutathione (Glu, Cys, Gly)

Glutathione conjugation

Glucuronide (X = O, N, or S)

UDP-alpha-D-glucuronate

Glucuronide formation

Product in vivo reactantProcess

Glutathione-s-transferase

Enzymes of the glutathione S-transferase (GST) family are compos

ed of many cytosolic , mitochondrial , and microsomal proteins .

GSTs catalyse a variety of reactions and accept endogenous and

xenobiotic substrates .

They are members of Membrane Ass ociated Proteins in Eicosanoid and Gl

utathione metabolism family oftransmembrane proteins.

XENOBIOTICS


Excretion


Phase IIConjugation


Polar Hydrophilic

Polar

Hydrophilic

XENOBIOTICS


Excretion


Phase IIConjugation


Polar Hydrophilic

Polar

Hydrophilic

Excretion of Toxins

Toxins leave the body through:

Kidney (Urine)Feces Lungs (e.g., mucus, breat

hing out)

Proteinase inhibitor

Plant also contain antinutritive compounds that make essential constituents unavailable for digestion by herbivores.

Inhibit the action of digestive protease enzymes in herbivores and thus make protein unavailable

However, careful work have reveled that although proteinase inhibitors effectively reduced the function of particular protease in the gut of six lepidopteran species, corresponding reduction in catepillar growth were minimal (Broadway, 1995,1997)

http://www.ysbl.york.ac.uk/~proteinase/

Salivary enzymes

Herbivores also produce salivary enzymes constitutively, prior to ingestion, that minimize the effectiveness of plant defenses.

Such enzymes are applied to leaf wounds as the herbivores chew and these may reduce the activation of induced defense in plants.

Salivary enzmes

Glucose oxidase is a major constituent of caterpillar saliva that appears to suppress early signaling events in plant defense (Felton and Eichenseer, 1999)

Glucose oxidase inhibits lipooxygenase activity, a critical step in the biosynthesis of the induction signal and thereby reduces induced resistance in plants

Caterpillars that were inhibited from producing glucose oxidase fed less and grew les, indicated that offense had been block (Musser et al, 2002)

Salivary enzymes

Other herbivores may also secrete saliva that interferes with plant defense.

Salivary constituent from grasshoppers have been implicated in enhanced growth of plant

In this case, the offensive strategy may be to stimulate plant growth. However, to the individual herbivores has not been demonstrated in this sample.


Herbivores that specialize on particular host plant often have very specific enzymatic systems that allow them metabolize the secondary chemicals of those hosts.

Sequestering host chemicals

Many herbivored incorpate or sequester the biologically active chemicals of their host plants into their own tissues or glands, and thereby gain protection from their predators and parasites (Duffey, 1980)


Sequestering host chemicals (Kargan & Agrawal, 2002)

The herbivore must willing to ingest the host’s secondary chemicals

The herbivores must be relatively tolerant of the chemicals

The herbivores must ingest the chemicals without metabolizing them into biologically inactive products

The herbivores must deposit the secondary chemicals in particular tissues, or otherwise store them.

http://www.biozentrum.uni-wuerzburg.de/fileadmin/REPORT/BOT2/bot2004.htm

Interactions between plant, herbivorous insects and carnivores

Sequestering host chemicals

Decorator crabs sequester protective chemicals behaviorally by attaching noxious plants to the outsides of their bodies and thereby reduce their risk of predation (Stachowicz and Hay, 1999)

http://www-eve.ucdavis.edu/stachowicz/decorator.shtml

Sequestering host chemicals (Kargan & Agrawal, 2002)

Sequestration may be relatively expensive as an offense strategy.

Although the strategy allows herbivores to save costs associated with synthesis of defensive chemicals, it often requires specialized structures to separate, selectively uptake, and/or modify plant compounds Bower,1992)

Common sense suggest that sequestration may require a very specialized diet.

Microbial symbionts

Herbivores are unable to digest complex cellulose and rely on mutualistic, internal symbiotic bacteria, fungi, or protozoa to break down cellulose so it can be used by the herbivore . Microbial symbionts also allow herbivores to eat plants that would otherwise be inedible by detoxifying plant

secondary metabolites.

Microbial symbionts

For example, fungal symbionts of cigarette beetles (Lasiode rma serricorne ) use certain plant allelochemicals as their

source of carbon, in addition to producing detoxification enzymes (esterases) to get rid of other toxins.

Thus, Symbionts may increase feeding and exploitation of plants by herbivores by providing nutrients, digestion and detoxification.

Microbial symbionts

More aggressive strategies involve inoculating hosts with microbes that mobilized nutrients or diminish plant defenses.

Herbivores that vector plant diseases (Thrips, beetle, mite, Homopterans) may manipulate plants to their won benefits through infection.

Microbial symbionts bark beetle introduce blue stain fungi of the genera and

into trees before feeding. The blue stain fungi cause lesions that reduce the trees’ defensive mechanisms and allow the bark beetles to feed

Gall and induced plant susceptibility Gall are plant structures that are inhabited

and fed upon by small herbivores (or by fungi or microorganisms)

These structures are made of plant tissue although gall morphology is controlled by the herbivores

Variation in the morphology of the gall depends upon the phylogeny of the gall-making insect and is independent of the host phylogeny.

Herbivores manipulates their host

–aggressive-

Gall and induced plant susceptibility Gall form is determined by substances secreted by

the oviposition female or by the spatial pattern of larval or adult feeding

Aphids that feed in galls are more efficient than free feeding aphids (Llewellyn, 1982)

This evidence implicates the induction of galls as probable offensive traits.

Galls provide the gall maker with a specific microhabitat that may include relative safety from pathogens, predators, and parasites as well as source of high quality nutrition (Weis&Kapelinski,1994)


–aggressive-

Gall and induced plant susceptibility These tactics can greatly reduce the

effectiveness of photoactive plant defense. Leaf rolling reduces light inside the roll and

this behavior was associated with reduction in leaf toughness and tannin concentration.

This tactic increase rates of development and decrease mortality of larvae and qualifies as offensive.


–aggressive-

Trenching, mowing, haying and gardening Plant can immobilized herbivore mouthparts

and reduce feeding by releasing secretions from pressurized canals such as lacifers when herbivores bite.

In response, many insects cut vein across the leaf blade prior to feeding.

The herbivores then feed beyond the cuts, free from the plant exudates that would normally deter herbivores.


–aggressive-

Trenching, mowing, haying and gardening Many insect herbivores reduce harmful effects of trichomes by

mowing them before feed. Some catepillars avoid trichromes by laying down a silk covering

or scaffolding over them


–aggressive-

Trenching, mowing, haying and gardening Certain mammalian herbivores clips vegetation and cache it

before consuming it, a behavior know as ‘haying’ (Vander wall,1990)

Plants cached in ‘hay piles’ facilitated food storage and also allowed toxin degrade so that cached food become much more palatable after storage (probable offense)


–aggressive-

Trenching, mowing, haying and gardening Leaf-cutting ants gather pieces of fresh leaves and flowers which

they use to culture fungi, their ultimate sources of nutrition


–aggressive-

VIDEO LINK

Gregarious feeding To enhance the ability of herbivores to exploit

their host plants. Enhanced host finding and reduce predation

risk Gregarious caterpillars grew twice as fast as

in large groups compare with a small groups of herbivores


–aggressive-

Richard Karban and Aunrag A. Agrawal. 2002. Herbivore offense. Annu. Rev.Ecol.Syst.33:641-64

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