10/27/2015

1

Variations on the theme of Digestion

Trophallaxis: ants (Hymenoptera: Formicidae)

Honeypot ants (repletes)

between castes

Food movement in gut• by peristalsis

• via peritrophic membrane

• antiperistalsis (necessary for trophallaxis)

10/27/2015

2

Trophallaxis: other insects

Social wasps brood

Termite workers queen

Burying beetles larvae

Omnivore: cockroach(highly variable)

Leaf specialist: imperial moth(2-3 hours for transit)

Speed of digestion: effect of dietary class

Carnivores: tiger beetle (10x herbivore)

Chemically stable:clothes moth

(2-4 days)

also: food type & amount; activity & hunger level; temperature, etc.

hair(keratin)

(many hosts)

10/27/2015

3

Filter chamber of Sternorrhyncha (Coccidae & Aphidae)

Ant-tending (mutualism)

Scale insects,Coccidae:

Efficiencyof digestion:• Circumstances.• Ecology (desert,

tropical, etc.).• Life history.• Concentration.• Type (solid, liquid,

complex, fibrous).• Liquid pressure

(turgor, etc.).

esophagus

esophagus

filter chamber(lateral view)

Mutualism: Plants, Ants, and Scale insects

Neotropical Acacia(hollow thorns)

Kibara(swollen internode)

Beltian bodies

coccids(phloemfeeders)

entranceholes

“Domatia”

(Evolutionary consequences of insects gettingrid of excess carbohydrates)

10/27/2015

4

Secretory cornicles (Aphidae) and mutualism.Reciprocity: real costs and benefits

analorgan

cornicle

Benefits:• excess carbos.

• sugar goo.

• fungus on goo.

• protection from predators.

• transport to new, fresh food.

Benefit for the ant:• Reliable food!

Costs:• exposure

to other predators.

• cornicleconstruction.

• biochemical machinery.

Secretory organs (Lycaenidae)and mutualism (reciprocity)

10/27/2015

5

More secretory organs (Lycaenidae) and mutualism (reciprocity)

Dorsal nectaryorgan

Pore cupolae

Pore cupola

(larvaeating

aphids)

Jalmenus evagoras

Sounds (vibrations)attract ants to tend

caterpillars

larva

pupa

grunts

drums

hisses

pu

pal

calls

strigil

larv

alca

lls

milliseconds

sec

msec

10/27/2015

6

Excretory products (Membracidae) and mutualism:Bi-product benefits rather than reciprocity

(no particular costs for the interaction)

(the treehopper “helmet”)

Extra-oral digestion: Ex. = syrphid fly larva

Methods used:• salivary glands

• mandibular glands

• regurgitation from midgut (Dytiscidae & neuropteran larvae)

Result: liquification

10/27/2015

7

Extra-oral digestion:Ex. = parasitic wasps

Pompilidae(liquify hosts)

Sphecidae

(cicada killer)

Silk “digestion” (Ex. = Polyphemus moth, Antheraea polyphemus)

10/27/2015

8

Wood digestion, 1: Just the Carbs

Death-watch beetle(Anobiidae: Xestobium)

Constituents of wood:• 40-60% cellulose

• 18-40% lignin (never utilized)

• 8-40% hemicellulose (Orthoptera)

• 5% starch, glucose, protein

Witchetty grub(Lepidoptera: Cossidae)

Powderpost beetle(Coleoptera: Lyctidae)

(Australia)

Wood (cellulose) digestion, 2: Actual cellulase

Coleoptera: Cerambycidae

Zygentoma: Lepisma

Orthoptera:Schistocerca

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Wood (cellulose) digestion, 3:

Gut symbionts

midgut bacteria:Tipula

hindgut bacteria:Scarabaeidae

hindgut flagellates: Mastotermes…

hindgut bacteria:Termitinae

…and Cryptocercus (2 shared genera)

(70% efficiency)

(1/3 ofbody

weight)

(note anal feedingand ingestion of

cast skins)

Keratin (hair & feathers) digestion

Clothes moth(Tineidae)

Bird lice(Psocodea:

Phthiraptera:Mallophaga)

Carpet beetles(Dermestidae)

(47% efficiency)

Methods:• strong reducing agents

• keratinase (rare)

• unknown pathway?

10/27/2015

10

Collagen digestion: warble flies (Hypoderma)

Collagenase (flies) & hyaluronidase (assassin bugs)

Wax digestion: wax moths (Pyralidae: Galleria spp.)

(50% efficiency via endosymbiotic bacteria in mycetocytes)