11/3/2015

1

Spiracle types and closure mechanisms: valves & atria

EXTERNAL-VALVED, ATRIATE SPIRACLE(with external Type 1 “lip closure”)

NON-VALVED,NON-ATRIATE SPIRACLE

INTERNAL-VALVED,ATRIATE SPIRACLE

closermuscle

dust-catchingsetae

atrium

lip

atriumclosermuscle

filter apparatus

ant spiracle(open) grasshopper spiracle

(closed)

Classification:• non-valved (non-

atriate & atriate

• external-valved (non-atriate & atriate)

• internal-valved (non-atriate & atriate

Spiracle types and closure, continued (all atriate)

EXTERNAL-VALVED(with Type 2 lip closure)

trachea

INTERNAL-VALVED(with opposed muscles)

INTERNAL-VALVED(occlusor muscle only)

occlusor

dilator

trachea

occlusor

elastic cuticularprocess

internalsclerotizedpad

internalcuticularprocess

trachea

occlusor muscle

head louse spiracle

valves

Atrial functions:• air filtration (dust & pollen)

• H2O conservation

• glandular secretions (stink)

• acoustics (courtship)Psocodea: Anoplura

11/3/2015

2

Trabeculae

armature

Protective hairsand teeth on lips

of spiracles

(often hydrofuge, i.e. non-wettable)

Spiracular filtering & humidifying devices (e.g. Orthoptera)

sieve plates

felt chambers

(a bit like the grillwork on

automobiles)

11/3/2015

3

Spiracular sound-making devices (e.g. Blaberidae)

Gromphadorhina portentosa:

Tracheal tube to 2nd abdominal spiracle has the form of an “exponential horn”

spiracle

Directional hearing in crickets (Orthoptera)

= mesothoracic spiracles

= tympanal organs in front tibiae MESOTHORACICSPIRACLE

11/3/2015

4

Capacitative loading of tymbals & earsin cicadas (Hemiptera)

tymbal

tympanum (ear)

tymbal muscle

tymbal

air sacs(provide acoustic loading

pleural & sternal phragmata

Magicicada septendecim

Aquatic respiratory (non-) adaptation:

Cutaneous diffusion in spongillafly larva (Neuroptera: Sisyridae)

Critical:• small size

• low needs

• cold temp

Also: 1st instar Simuliidae, Chironomidae (Diptera)

tracheal system“closed” or not present

0.25" long

11/3/2015

5

Aedesmosquito

larva

hydrofuge hairsseparated

“snorkel”(Ranatra: Hemiptera)

hairs closed over spiracle

O2

O2

CO2

air

Tracheal gills• Odonata• Ephemeroptera• Plecoptera• Megaloptera• Trichoptera

damselflynaiad

Aquatic respiratory adaptations: gills & siphons

“closed”system

“open” trachealsystem

Siphons• Hemiptera• Diptera

N2+O2

Culex pipiens life cycle (Diptera: Culicidae)

“open”

larva(wriggler)

pupa

11/3/2015

6

Aquatic respiratory adaptations: bubbles in beetles & bugs

Dytiscusbeetle:

under elytraHydrophilidaebeetle: ventral

sternal“keel”

Notonectidae, Hemipteradorsal & ventral

“open”

water strider:Gerridae, Gerris

Aquatic Hemiptera: four families, siphons & bubbles (& just skaters)

water boatman:Corixidae, Corixa

water scorpion:Nepidae, Nepa

backswimmer:Notonectidae, Notonecta

11/3/2015

7

Aquatic respiration by an air bubble:Dytiscus (Coleoptera: Dytiscidae)

subelytral cavity

trachea

air

“open” system spiracle

openings

epitheliumcuticular

filaments ofend of trachea

(spiracle)

plastron hairs(microtrichia)

AIR

H2O

H2O

H2O

5 μ

macroplastron

plastron100μ

Hydrophilus (Coleoptera)

Elmis (Coleoptera)

20 μ hairs flattened

hairserect

“riffle beetle”

“creepingwater bug”

“Open” system:

Gaseous plastron – Aphelocheirus (Hemiptera)Has been likened to a “physical gill.”

11/3/2015

8

Gaseous plastron – Aphelocheirus (Hemiptera), detail

Spiracular rosetteTiny circles & buds are minute

openings of the spiracle.

Note the importance of AIR in the “physical gill,” not just O2

Blood gills (Ex. = anus of Simulium pictipes larva – Diptera)

Typical adult “black fly”

No trachealsystem:

hemolymph

11/3/2015

9

Spiracular gills (Ex. = Hydroscapha natans – Coleoptera)

larva

adults

actualsize

Everted trachealsystem (closed)

Hemoglobin for respiration(Ex = Chironomus spp. – Diptera)

Heterogeneous subunits aggregate upon deoxygenation; they control release of O2 into a gas bubble, allowing mid-water position.(energy conservation)

An association-disassociation equilibrium

Live where O2 is at low tension.Facultative presence of hemoglobin (w/ 27x O2 affinity of vertebrate form).

No tracheal system in larvae.

Hemoglobin for buoyancyand respiration

(Ex. = Anisops sp. –Notonectidae, Hemiptera)

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10

Mansonia and Coquillettidiamosquito larvae

(Diptera: Culicidae)

Other orders:• Coleoptera• more Diptera

teeth

saw

Respiratory siphonfor puncturing plant stems

(“Open” system, as in all siphon breathers)

spiracle(aroundspiracle)

trachea

Tapping underwater plant stems for air in Donacia(a “long-horned” leaf beetle – Coleoptera: Chrysomelidae)

11/3/2015

11

Tapping underwater plant stems for air in Chrysogaster(Syrphidae: Diptera)

spiracle

(Larvae live in mud & ooze as detritivores)

abdominalspiracles

“Aquatic” endoparasite: Hypoderma larva

“head”

(“Open” system, as in all siphon breathers) spiracle

mouth hooks

Also: tapping tracheae and caudal filaments(Diptera: Tachinidae)

11/3/2015

12

Pontomyia sp. (Diptera: Chironomidae) – a marine insect

lagoons & tide pools

Male (female is larva-like & subaquatic. Adults live

only a few hours.)

Reduced wing –Skate on water instead of fly

Marine invasions: RARE• only Collembola plus a few Hemiptera,

Trichoptera, Diptera, & Coleoptera

• Why not? Probably biotic/historicalconstraints (Crustacea got there first!)

Halobates fijiensis, another marine insect (Hemiptera: Gerridae)

Distribution of juveniles along upper shore and mangrove transects

Distribution along an open-water transect

high tide

lowtide

high tide

juveniles

adults

11/3/2015

13

Pattern of Circulation

wing heart

excurrent ostium incurrentostium

dorsal & ventral septa with fenestrae at edges

nervecordheart

ganglionleg

extension ofventral septum

legdorsal vessel

(aorta)

leg ampulla

antenna

antennalampulla

wingampulla

alary (aliform)muscle

aorta ordorsal vessel

dorsaldiaphragm

tergo-sternalmuscle

heart

segmental orlateral vessel

incurrentostium

segmental orlateral vessel

Segmental vesselsin Blaberus(2 pairs thoracic,

4 pairs abdominal)