Respiration Diet Specializations. General Organization. Openings leads to system of pipes. spiracles openings to the respiratory system

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Beverly Dean
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1 Respiration Diet Specializations 1. Respiratory systems a. Anatomy b. Air movements c. Gas exchange d. Respiratory pigments?! 2. Digestive systems a. Mouthparts and diet b. Major gut divisions (structure and function for each section) c. Integrating digestive and excretory systems for water balance Openings leads to system of pipes General Organization Longitudinal trunks: lateral dorsal, ventral Cross wise tracheae: dorsal, ventral visceral Major branches extend up, down and in spiracles openings to the respiratory system 1

spiracles can be permanently open permanently closed able to

Tracheal structure lined with cuticle branch and join finest

shed at molt taenidia for strength Tracheal structure Tissue

withstand negative pressure tracheoles and tracheole cells

active tissue, tracheoles reach near mitochondria atmosphere

2 spiracles can be permanently open permanently closed able to open and close respond to neural input or directly to CO 2 Tracheal structure lined with cuticle branch and join finest branches are intracellular tracheal epithelial cells cuticle shed at molt taenidia for strength Tracheal structure Tissue dissolved away - slinky like structure obvious must withstand negative pressure tracheoles and tracheole cells tracheoles keep cuticle at molt intracellular tracheoles in active tissue, tracheoles reach near mitochondria atmosphere oxygen diffuses into tissue CO2 released from tissue into tracheole 2

? it s the physics Diffusion of oxygen oxygen in air diffuses >100,000 times faster than in water or tissues Carbon

3 Systems with air sacs taenidia reduced or absent collapse under pressure important in ventilation forced air movements NOT lungs open (to the air) respiratory systems closed respiratory systems How can a closed respiratory system work?? it s the physics Diffusion of oxygen oxygen in air diffuses >100,000 times faster than in water or tissues Carbon dioxide diffuses 10,000 times faster so... Diffusion of oxygen faster from spiracle to tracheole than from tracheole to mitochondria 3

times, with ventilation, can create flow in one direction resting ventilation, example hyperventilation -

4 Gas Exchange Ventilation Internal air movement Diffusion ventilation at rest, most of the time all spiracles closed air goes in and out of a spiracle- tidal flow opening and closing spiracles at different times, with ventilation, can create flow in one direction resting ventilation, example hyperventilation - time all closed is reduced - continuous in flight, all spiracles are used Internal compression inspiration expiration 4

5 What is going on with actual gas exchange? development of equipment that can measure very small changes in gas levels allows study of this question Gas Exchange with Working Spiracles research dependent on technical equipment that can measure very small changes in gas concentrations in tiny spaces Three general patterns of respiration in insects (discontinuous gas exchange cycle = DGEC) discontinuous disc., no long closed period continuous in resting insects (easiest to study) measurements have shown that gas exchange occurs in distinct bursts especially extreme in pupae Recordings of CO2 release (Ai-Ci) and water loss Gibbs, A. G. et al. J Exp Biol 2004;207: Cecropia pupa 3 spiracle phases takes a breath every 8 hours Closed Flutter Fully open 5

6 end of open phase gradient favors diffusion out of CO2, H2O spiracle closed, CO2 build up, no change in H20 spiracle opens gradient for CO2 flow out high, H20 always the same Start with Closed Phase po2 falls Pressure falls Flutter begins Pressure equalizes Build up of CO2 triggers spiracle to open O2 triggers closure CO2 release po2 pressure What is the functional significance of DGE? Reduce respiratory water loss? Protection from toxic oxygen? Manipulate oxygen levels Red line is oxygen level in atmosphere Green lines are CO2 release Blue line is the O2 level inside tracheae 2005 Nature 433:516 At low oxygen At high oxygen Oxygen levels constant Spiracles open often to allow more oxygen to get in Frequent small releases of CO2 Spiracles rarely open Oxygen level trachea the same as in low oxygen conditions 6

7 Oxygen nicely regulated! oxygen levels (PO2) are constant regardless of oxygen level Oxygen is a poison! When photosynthesis evolved, atmosphere started accumulating oxygen Water is split (CO2+H20=CH2+O2), Oxygen attacks chemical bonds, very corrosive New systems had to evolve to deal with it Think how corrosive pure oxygen is to us, even now Think how antioxidants are good for you Using DGE, insects reduce gas exchange to reduce toxic effect of oxygen that is not being used quickly Cycle disappears in active, flying insects. Oxygen is being used quickly Insect respiratory system functions most efficiently at high levels of oxygen consumption What is the functional significance of DGE? Reduce respiratory water loss? YES? Protection from toxic oxygen? YES Respiratory pigments? 7

HEMOCYANIN Archeognatha Thysanura Orthoptera Dermaptera Isoptera Hemocyanin common in spiders,

didn t need it because they live in a relatively high oxygen environment Hemocyanin in insects

tissue cells Hemoglobin larval Chironomus - midge Gasterophilus -a dipteran parasite HEMOGLOBI

8 HEMOCYANIN Archeognatha Thysanura Orthoptera Dermaptera Isoptera Hemocyanin common in spiders, Crustacea, mollusks copper carries oxygen, gives it a blue color previously believed insects didn t need it because they live in a relatively high oxygen environment Hemocyanin in insects Perla a stonefly, carries functional hemocyanin in its blood In the other groups, it is found in tissue cells Hemoglobin larval Chironomus - midge Gasterophilus -a dipteran parasite HEMOGLOBI Hemiptera Coleoptera Lepidoptera Diptera Hymenoptera Hemoglobin in insects in hemolymph of Chironomus 8

Chironomus larval chironomids are called "blood worms" they contain a small hemoglobin with high affinity for oxygen allows them to extract oxygen from water in low oxygen environments the only

9 Chironomus larval chironomids are called "blood worms" they contain a small hemoglobin with high affinity for oxygen allows them to extract oxygen from water in low oxygen environments the only insect (so far) that has Hb in its blood Hemoglobin in Drosophila and Apis Found in tissues, not in hemolymph J. Biol. Chem. 277(32):29012 (2002) Hemoglobin in Drosophila A. very early embryo B. yolk sac C,D. fat body E. tracheal cells ADULTS F. tracheal cells G. fat body cells H. late oogenesis J. Biol. Chem. 277(32):29012 (2002) Diffusion of oxygen remember that diffusion of oxygen through tissue between the tracheole and mitochondria is slow Hemoglobin Location in tracheoles may allow steady oxygen flow to mitochondria when oxygen content of air varies? Non-toxic store of oxygen relationship of INSECT HEMOCYANINS to other arthropod hemocyanins higher insects have lost them (have a new function!) 9

storage proteins Insect diets vary widely

plants Solids, liquids Wide range of food

10 Did hemocyanins vanish in most insects? No, they morphed into related proteins called hexamerins, or storage proteins Allows insects to store amino acids! storage proteins Insect diets vary widely Food Processing I. basic equipment + diversity II. designs for floods and droughts Animals, plants Solids, liquids Wide range of food types generalists, scavengers Narrow range of food types specialists Mouthparts, gut structure. vary widely and reflect diet 10

11 consider my head and its mouthparts labrum mandible maxillae labium Hypopharynx labrum mandibles maxillae labium 11

cuticle lined overall unsclerotized but can have sclerotized spines foregut regions pharynx esophagus

12 mouthparts any of the parts can be modified modified parts work together to make a mouth that functions completely differently from other plans Your basic gut foregut - general features FOREGUT MIDGUT HINDGUT cuticle lined overall unsclerotized but can have sclerotized spines foregut regions pharynx esophagus crop proventriculus grasshopper pharynx-crop pharynx especially has muscles muscles give the ability to PUMP 12

pharyngeal pump - Lepidoptera Lepidoptera pharyngeal pump -

esophagus crop proventriculus pharynx esophagus crop

Diptera and Lepidoptera have permanent sac The capacity of the

13 pharyngeal pump - Lepidoptera Lepidoptera pharyngeal pump - plant fluid feeds foregut regions foregut regions pharynx esophagus crop proventriculus pharynx esophagus crop proventriculus crop Honeypot ants storage extensible part of gut Diptera and Lepidoptera have permanent sac The capacity of the CROP can be enormous. Quality of cuticle (impermeability) important in ability to store 13

characters FOREGUT MIDGUT HINDGUT Midgut - general features Caeca = ventriculus NOT lined with cuticle gastric caeca secretes

14 foregut regions along its length proventriculus pharynx esophagus crop proventriculus anterior part of valve between foregut and midgut variable form proventricular spines Your basic gut midgut orthopteroid insects push and tear food good species specific characters FOREGUT MIDGUT HINDGUT Midgut - general features Caeca = ventriculus NOT lined with cuticle gastric caeca secretes enzymes absorbs nutrients secretes peritrophic envelope increase absorptive surface area? often contain microorganisms, possible symbionts 14

Midgut secretes peritrophic envelope/matrix type I forms over surface of midgut type 2 secreted anteriorly forms lining for midgut found in most insects but not most Hemiptera can form in response to

compartmentalizes digestion for greater efficiency 3.

15 Midgut secretes peritrophic envelope/matrix type I forms over surface of midgut type 2 secreted anteriorly forms lining for midgut found in most insects but not most Hemiptera can form in response to one food (blood) but not another (nectar) peritrophic envelope function of the peritrophic envelope? 1. mechanical barrier from abrasion, pathogens, enzymes 2. compartmentalizes digestion for greater efficiency 3. biochemical barrier neutralizing toxins Composition of the matrix chitin fibrils linked by proteins glycans fill spaces properties of matrix depend on specific ion content and ph separate lumen into two spaces this allows compartmentalization of enzyme activity for different materials more efficient absorption as digested material moves into space next to gut wall Insect counter defense? Plants have defenses against insects One strategy is to contain compounds that will cause free radicals to form in insect herbivores Many plants contain enough iron to trigger free radical formation collected the peritrophic envelopes 15

The Experiment feed caterpillars artificial diet with different amounts of iron excreted peritrophic envelope contained the iron = PM scavenges iron Does this protect the insect when radical

tannin and iron add a chemical that disrupts membrane = damage when chemical added = it really is the PM that is providing protection More new protective abilities for PM Heliothis virescens (tobacco

16 The Experiment feed caterpillars artificial diet with different amounts of iron excreted peritrophic envelope contained the iron = PM scavenges iron Does this protect the insect when radical producing compounds are present? add tannins, different iron levels measure damage =total protection! What happens when you repeat experiment and remove PM? tannin and iron add a chemical that disrupts membrane = damage when chemical added = it really is the PM that is providing protection More new protective abilities for PM Heliothis virescens (tobacco budworm) - protects against baculovirus infection Aedes aegypti PM protein binds heme (iron) Midgut subdivisions Midgut subdivisions Hemiptera often have midgut subdivided into several specialized regions important for elimination of water and for housing micro-organisms 16

hindgut - general features ileum, colon, rectum pyloric valve between hindgut and midgut Malpighian tubules (kidney

somewhere in the hindgut features to provide retention of these microbes How do insects obtain water?

surplus constant deficit Dealing with imbalance requires integrating digestive system with excretory system Machinery

17 hindgut - general features ileum, colon, rectum pyloric valve between hindgut and midgut Malpighian tubules (kidney tubes) attach below valve - great landmark lined with cuticle very permeable hindgut symbionts are often housed somewhere in the hindgut features to provide retention of these microbes How do insects obtain water? Specialized diets with water imbalance in their food blood plant fluids flour, grain short term surplus constant surplus constant deficit Dealing with imbalance requires integrating digestive system with excretory system Machinery for balancing water, ions malpighian tubules digestive system 1) attachment site 2) cross-section structure basic structure of malpighian tubules 17

Rhodnius prolixus short term surplus feeds ~ once in

it can go hide kidneys (MTs) go to work blood

tubule to increase activity ions pumped in, water

water recovery moves water/ions from food to blood

important rectal pads pads of transporting cells

water and ions can be selectively recovered using

18 Rhodnius prolixus short term surplus feeds ~ once in 6 months huge meal must get rid of water quickly so it can go hide kidneys (MTs) go to work blood feeders short term surpluses hormonal activation of tubule to increase activity ions pumped in, water follows Shortage of water Digestive system helps in water recovery moves water/ions from food to blood recovering water/ions in urine water recovery VERY important rectal pads pads of transporting cells good tracheal supply indicates metabolic activity water and ions can be selectively recovered using malpighian tubules + gut to recover water cryptonephridial arrangement 18

What do animals do to survive?

What do animals do to survive? Section 26-1 All Animals have are carry out Eukaryotic cells with Heterotrophs Essential functions such as No cell walls Feeding Respiration Circulation Excretion Response