8. respiration and circulation

5 functions of circulatory system

• nutrient delivery

• hydrostatic pressure

• immune response

• clotting

• thermoregulation

hemolymph

blood

hemocoel

body cavity

describe the open circulatory system

hemolymph (blood) is released into the open hemocoel (body cavity) to circulate

function of tubular dorsal vessel

pumps hemolymph anteriorly into the pulsatile heart (abdomen) and aorta (thorax and head)

parts of pulsatile heart

• allary muscles

• ostia

alary muscles

at every chamber/segment of pulsatile heart, create rhythmic pumping

ostia

paired one-way valves at each chamber

incurrent ostia vs. excurrent ostia

incurrent ostia along heart

excurrent ostia at ends

heartbeat is __ but gets __ and __ signaling

myogenic, neuronal, endocrine

contractile wave mostly moves…

anteriorly

can contractile waves of the heart reverse?

yes — can reverse in pupae in response to anterior pressure

2 functions of alary muscles for heartbeat

• dilate heart chambers

• draw hemolymph through incurrent ostia

ventral and dorsal diaphragms

guide hemolymph into sinuses by forming channels and pulsating

accessory hearts

circulate hemolymph thru appendages (legs, wings, antennae, ovipositor)

hematopoietic organ/lymph gland

• houses stem cells and releases mature hemocytes

• usually in close association w dorsal vessel

6 substances that make up the hemolymph

• ions

• circulating sugars and AAs

• hemocytes

• circulating metabolic compounds (yolk proteins, lipid chaperones, etc.)

• defensive chemicals (synthesized or sequestered)

• endocrine signals

trehalose

disaccharide w antifreeze function

• necessary because we need glucose to diffuse to extremities. however, that would mean [glucose] would be so high that it would COUNTER its gradient from gut to hemolymph

• to resolve this, we rapidly convert glucose to trehalose for nutrient delivery

fat bodies + location and functions

lobed ribbon-like sheets of storage cells distributed throughout the hemocoel

close proximity to the heart and midgut (no capillaries)

functions: metabolic regulation, secretions into hemolymph

describe fat bodies’ involvement in metabolic regulation

• fat bodies synthesize trehalose from glucose for immediate circulation

• triglycerides and glycogen are stored in lipid droplets for induced energy release

4 things fat bodies secrete into the hemolymph

• lipophorins - lipid chaperones

• vitellogenins - yolk protein for provisioning eggs

• hormones involved in molting

• antimicrobial proteins

which number is the fat body?

2

(1 is ootheca, 2 is fat body, 3 is nerve ganglion, 4 is ventral nerve cord)

eclosion

process of hatching from an egg/cocoon

ex:

• fly “ptilinum”

• inflating wings

• molting from exuviae at suture lines

what do caterpillars’ prolegs rely on to function?

hydrostatic pressure

what are male moth “coremata” used for?

phermone release

what must humoral compounds recognize to induce cellular responses?

“universal” molecular signatures

• prior exposure sensitizes subsequent responses (but not adaptive immunity)

• less expensive than adaptive immunity

• less flexible

pattern recognition receptors

• involved in immune response

• bind specific molecular signatures associated w microbes

• trigger signaling cascades to induce cellular and humeral responses

3 types of hemocytes

• prohemocytes

• phagocytes

• enzyme producing (oenocytoids, crystal cells)

prohemocytes

undifferentiated precursors to all other hemocytes

phagocytes

• consume cellular debris

• encapsulating: flatten to engulf microorganisms

enzyme producing

oenocytoids, crystal cells

• store enzymes that induce formation of melanin and toxic compounds

3 cellular immune responses

• phagocytosis

• encapsulation

• nodulation

phagocytosis

singular target, phagocyte engulfs that one pathogen into itself

encapsulation

target is a small number of large pathogens

nodulation

target is a large number of small pathogens

cellular encapsulation and nodulation

involves phagocytes surrounding the pathogens

melanization in encapsulation and nodulation

oenocytoids release enzymes to melanize

polyDNA viruses

• parasitic wasps inject polyDNA viruses along w eggs

• they don’t kill host cells — instead, they cause production of proteins that suppress;

  • molting and growth

  • production of antimicrobial compounds

  • encapsulation

  • melanization

• … which prevent the wasp egg from being killed

2 steps to clotting

• hemolymph thickens when exposed to air (forms a gel)

• hemocytes aggregate and melanize (similar to encapsulation response)

insects are generally (exothermic/endothermic)?

exothermic

antifreeze agents

polypeptides that bind ice nuclei as they form and lower the freezing point → often parallel secondary structures

• an exception to insects being Mostly exothermic

muscle-based thermogenesis

contracting flight muscles heats up blood which is then circulated

• another exception to insects being Mostly exothermic

tracheal system

primary respiratory system of insects. a complex system of hollow vessels where O2 and CO2 are passively exchanged

tracheoles

large trachea narrow into these, which innervate tissue (muscles, brain, gut, etc.)

spiracles

• valves to the tracheal system

• muscular — can be opened or closed

• can also prevent water loss

when do spiracles open?

during “energetic” behavior

spiracle pairs for standard vs. aquatic vs. gills

“standard” - 10/9/8 spiracle pairs

aquatic - 1/2 spiracle pairs

gills (aquatic) - no spiracles

intima

cuticular layer formed by tracheal epithelium secreting chitin

taenidium

cuticular spirals within intima

• provides support but also allows some compression

are trachea or tracheoles shed during molting?

tracheoles

describe wing expansion

as fluid is pumped into the wing veins, trachea compress to enable wing expansion

air sacs

used for “active” respiration

• these are enlarged trachea which form sacs

• sacs are vented to increase air exchange

• diving beetles may also use sace for buoyancy

abdominal venting

used for “active” respiration

• various sclerite movements compress trachea to force air exchange

physical “gills”

air bubble exchanges O2 with water

plastron layer

part of physical “gills,” cuticular hairs that capture a thin, constant layer of air that connects to spiracles

how do diving beetles use their physical “gills”?

(keep in mind they don’t actually have gills)

• diving beetles trap bubbles under elytra, but must resurface due to differences in SA:V ratio

biological “gills”

air exchange across cuticle of gills

• gills are appendages → flapped to increase water flow

siphon

a “snorkel” with hairs to prevent water entry

hemoglobin in respiratory systems

AN EXCEPTION — most insects lack hemoglobin

• blood worms (larvae of some midges) live in lake sediment (extreme hypoxia)

• possess free hemoglobin in blood to fix oxygen (thus its red color)