ENT 220 Midterm

How many segments are in the head?

6

How many segments are in the thorax?

3

Plates in thorax

Notum (dorsal), Pleuron (lateral), Sternum (ventral)

How many segments are in the abdomen?

11

Dorsal, lateral ventral plates in the abdomen

Tergum (dorsal), Pleural membrane (lateral), Sternum (ventral)

Functions of the integument/exoskeleton

• Resistancetodryingout

• Metamorphosis

• Sensory and neuro-motor sophistication

• Mobile winged adults

Layers in the Cuticle

• EPIcuticle

• PROcuticle

  • EXOcuticle

  • ENDOcuticle

Layers in the integument

Cuticle and epidermis

5 layers in the epicuticle

Lacks chitin

• cement layer

• wax layer

• superficial layer

• Outer epicuticle

• Inner epicuticle

What is chitin made of?

Rotating bundles of N-acetyl-D-glucosamine polymers

Sclerotization

Hydrogen bonding of chitin chains, Quinones (phenolic bridges) link proteins, Dehydration of protein chains

Arthrodial membrane

Unsclerotized cuticle, in between joints, caterpillar skin

Cuticle benefits

• water movement

• protection

• barrier to pathogens and predators

• crypsis

• waste products (pigment, chemicals)

• attaching muscles, provides leverage

Cuticle disadvantages

• specific modifications for gas exchange

• specific modifications for sensory reception

• restriction on growth

• molting- vulnerable physically, chemically, osmotically

• Energetic cost of new exoskeleton that must be larger than the old one

5 Main sclerites in the head

vertex, gena, frons, clypeus, labrum

5 main mouthparts

Labrum, Mandibles (2), Maxillae (2) Hypopharynx, Labium

Prognathous

Forward jaw

Opisthognathous

Behind jaw

Hypognathous

Under jaw

Maxillary and labial palps function

chemosensory

Parts that make up the preoral cavity

Chemosensory

Suctorial Mouthparts

nectar feeding in Lepidoptera through proboscis

Piercing-sucking mouthparts

Wide variety of distantly related insects consume liquid food: herbivores (cicada), parasites (mosquitoes), adult fleas, carnivores (assassin bugs), elongated and toothed stylets enclosed by sheath (labium)

Sponging/lapping mouthparts

modifiedmouthpartsof “higher” flies (“suborder” Brachycera)

Chewing-lapping mouthparts

occur in adult bees; mouthparts modified to consume nectar and honey

Galea

elongated maxillae held together by spines and hooks, part of the proboscis, extended by increase in hemolymph pressure, coiled due to elasticity of cuticle and contraction of muscles, nectar sucked up by Cibarium

Hemiptera piercing and sucking mouthparts adaptations

• Mandibles are long stylets

• Maxillae form long interlocking stylets that form anterior food canal and posterior salivary canal

• Efficient muscular pumps in head

• All palpi lost and labrum reduced

• Labium forms long, protective sheath

Mosquito special piercing and sucking mouthparts

Labium -Labellar lobes (modified palpi) for mopping up blood

Mosquito piercing and sucking mouthparts - 6 stylets

• Scissor-like mandibles (2)

• Drill-like maxillae (laciniae-mesial lobe of maxillary stipes) (2)

• Labrum-epipharynx long, sharp— forms food canal (1)

• Hypopharynx long, sharp— contains salivary canal (1)

Tsetse fly (Glossinidae) piercing and sucking mouthparts

• Mandibles and maxillae lost

• Labrum, hypopharynx, labium and maxillary palpi present and similar to mosquitoes

• Labium with protrusible, spiny tip (piercing)

Stablefly (Muscidae) special piercing and sucking mouthparts

Rasping labellar lobes

House fly sponging mouthparts

labellar lobes with pseudotracheae modified for sponging up liquid food

Pseudotracheae

Open tubes that funnel food to the food canal in labrum

Horse flies piercing & sponging mouthparts

Mandibles, maxillae, hypopharynx swords, Labium with pseudotracheae, food canal formed by labrum-epipharynx & hypopharynx

Honeybees and bumblebees chewing-lapping mouthparts

• “Tongue”: glossae (labium)

• Surrounded by tube formed by galea (maxillae) and labial palp

• Sucking pump and tongue draw up nectar

• Mandibles not directly used in feeding

Maggot rasping mouthparts

Highly reduced, mouth hooks used for rasping, Myiasis, predation, decomposing

Odonata (dragonflies, damselflies) Seizing-Grasping mouthparts

Labium elongate, grasping and prehensile hooks, Thoracic / abdominal muscle contraction = hemolymph pressure

Neuroptera & diving beetle larvae Mandibulosuctorial mouthparts

Mandibles & maxillae form scythe-like feeding tubes, contain salivary (poison) canal

Aquatic filtering adaptations in Diptera (Fly) larvae

Labrum with brushes: feeding currents in mosquitoes

Antennae: grasping food

1st body segment name

PROthorax and FOREleg

2nd body segment name

MESOthorax, MIDleg, FOREwings

3rd body segment name

METAthorax, HINDleg, HINDwings

Thoracic sclerites

Notum (dorsal); Pleuron (lateral); Sternum (ventral)

PTEROthorax

Consists of the MESO and METAthorax

Pleuron sclerite sections

episternum (anterior) and epimeron (posterior) by pleural suture (ridge)

Specialized legs for cursorial locomotion

elongate, more distance, less effort, well developed femora and tibiae on all legs

Specialized legs for SALTATORIAL locomotion

Located on metathorax (HINDLEG), Enlarged femora/tibiae, Legs anchored by tarsal claws/pads, stored elastic energy released

Specialized legs for NATATORIAL locomotion

mid and hind legs flattened, row of setae (tibia and/or

tarsi), anterior movement, legs rotated

Specialized legs for FOSSORIAL locomotion

forelegs modified for digging, toothed projections from femur/tibia to rake soil, tarsi reduced

Specialized legs for RAPTORIAL locomotion

generally located on prothorax, to grasp prey for feeding, metathoracic in some parasitic wasps, “hanging flies”, large depressor muscles

Function of wing remigium

power & movement

8 main veins in wings

• pre costa (PC)

• costa (C)

• sub costa (Sc)

• radius (R)

• media (M)

• cubitus (Cu)

• anal (A)

• jugal (J)

Tegmina

Thickened leathery forewing modification

Elytra

Hardened forewings in beetles (Coleoptera)

Hemelytra

Forewings have a thickened base; Apical is membranous, in Heteroptera (true bugs)

Haltere

Reduced wings that act as a stabilizer or balancer

Which body segments bear genitalia?

8 and 9

How many body segments are in the abdomen?

11

Appendicular (“true”) ovipositors

Formed from appendages of A8 and A9, have 3 pairs of valves, Primitive condition, in some Odonata, Orthoptera, some Hemiptera, Hymenoptera

Substitutional ovipositors

Composed of extensible posterior abdominal segments, derived convergently several times, in Lepidoptera, Coleoptera, Diptera, Terminalia is telescopic, Manipulated by muscles attached to apodemes

Aedeagus

whole copulatory organ, structures of ninth abdominal segment, includes sclerotized penis

Stomodeum

Foregut, ectoderm and replaced at molt

Mesenteron

Midgut, endoderm and retained at molt

Proctodeum

Hindgut, ectoderm, replaced at molt

Digestion process

1. Grinding in the preoral cavity

2. Swallow with muscular pharynx

3. Food to esophagus

4. Crop for storage

5. Proventriculus to regulate food passage

Cibarium

Forms upper area of the pre-oral cavity

Salivarium

Forms lower area of the preoral cavity, connection to salivary glands

Dilator muscles

In the preoral cavity, made of pharyngeal muscles and cibarial pump

Proventriculus

Located in the preoral cavity, has grinding teeth

Peritrophic membrane

Located in the midgut, Formed by chitin, surrounds food bolus, permeable to enzymes, protects epithelial cells, compartmentalizes digestion (cyclic), secreted with feces

Structures located in the midgut

• gastric caecae increase surface area for nutrient absorption

• gut epithelium one cell layer thick

• epithelial cells produce and secrete enzymes (lipases, amylases, proteases)

• peritrophic membrane protects epithelium

• after digestion pyloric valve relaxes-remaining material to hindgut

Modifications to digest liquid food

• Narrowing of mouth tube to increase liquid flow

• Esophageal diverticulum to store liquid

• Salivary gland secrete or regurgitate ventricular fluids (Anticoagulants,toxins, histolysing)

Filter chamber

• digestive specialization

• Anterior and posterior section of midgut touch in enclosed membrane

• water shunted to hindgut

• food concentrated in midgut

• In many Hemiptera

• osmoregulation not disturbed

• Used for sap because of low nutrients in it

Function of the foregut

• Resorption of water and ions (NA+, K+,CL–)

• Defined by entry of Malpighian tubules

• Rectum

• Concentrates waste while avoiding toxicity (e.g. Nitrogen)

• Often houses bacterial endosymbiont

Insect symbionts

• Bacteria/protozoa/fungi in gut

• Provide sterols for moulting and carotenoids for eyes

• May have to reinoculate/relocate post-molt

• Sit in midgut

Malpighian tubules

• in the foregut

• Outgrowth of the alimentary canal

• Ends freely in the body cavity

• Range 2 or > 200. Aphids only insects without them

• Produce filtrate from hemolymph

Cryptonephric system

• preserve water in dry habitats

• distal end of the Malpighian tubules are in contact with the rectum

• ex. Tenebrio molitor

Function of the rectum

• reabsorb water

• Rectal epithelium thickened to form rectal pads

• Specialized cells in rectal pads carry out active recovery of Cl-

• Pumping Cl- creates electrical and osmotic gradients for absorption of H2O, salts, sugars and amino acids

Bug nitrogenous waste types

• ammonia: highly toxic

• uric acid: less toxic, store N

• Urea: rare

Fat body

• Equivalent to vertebrate liver

• Synthesizes, stores, and metabolizes fats, carbohydrates, proteins

• Loose network of cells associated with connective tissues of body

• site of glycogen deposition and storage

• Stores insect yolk vitellogenins

• Releases Trehalose (blood sugar)

Hemocoel

insect body cavity, with sinuses separated by septa, has hemolymph

Hemolymph function

• Nutrient transport

• Waste transport

• Hormone transport

• Heat transfer

• Chemical defense

• Hydrostatic skeleton (soft larvae)

• Hatching, molting

• Wing enlargement

• Movement

What is Hemolymph made of?

Plasma (liquid) + Hemocytes (blood cells)

What is circulatory plasma made of?

• Water (50-90%)

• Inorganic ions (varies with diet)

• Waste (uric acid)

• Organic acids

• Sugars

• Mainly trehalose; (glycerol in some)

• Lipids

• Hexamerins→storage proteins

• Lipophorin→transport lipids

• JH-binding proteins (juvenile hormone)

4 main Hemocyte functions

1. Phagocytosis

2. Encapsulation of parasites and large foreign material

3. Hemolymph coagulation

4. Storage and distribution of nutrients

   Does not carry oxygen

Dorsal vessel

• “heart”

• Simple tube of myocardial cells

• Lies in pericardial sinus above dorsal diaphragm

Dorsal diaphragm

• in the circulatory system

• Connective tissue

• Alary muscles move fluid up

• Support dorsal vessel

• Has septa

Ostia

Segmentally arranged openings of dorsal vessel for hemolymph, Act as one-way valves

Circulatory pathway

1. Enters pericardial sinus

   • Via dorsal diaphragm septa

   • Posterior end

2. Moves to dorsal vessel – Via ostia

3. Dorsal vessel contracts – Posterior to anterior

4. Leaves aorta

5. Circulates postero-ventrally – expansion of the abdomen, anterior to posterior

Ventral diaphragm

• Fibromuscular septum

• Aids circulation

• Peristaltic contractions

• Pumps hemolymph backwards & laterally in perineural sinus

• No ostia

Accessory pulsatile organs

• pumps blood to but not inside appendages

• Pumps blood to base of antennae, wings, legs, cerci

Spiracles

• External openings

• Up to 10 pairs: 2 thoracic; 8 abdominal

• Lack of O2 or build-up of CO2 initiates opening

• Closed most of the time for water conservation

Tracheae

• Develop as paired invaginations of epidermis (ectodermal origin)

• Has sclerotized taenidia for support

• Shed at molting

Tracheoles

• Fine tubules of gas exchange system that contact cells

• <1 μm diameter

• Not always shed at moulting

Taenidia

• Sclerotized spiral thickenings for tracheal support

• Flexible but resists compression

Intima

• ectodermally derived internal cuticle

• inner lining of tracheae, foregut, hindgut

• In tracheae: has wax, cuticulin, and chitin layers

• shed during molt

• helps prevent O2 absorption and H2O loss

3 phase discontinuous gas exchange

• Closed spiracular phase→consume O2 from tracheae, levels drop

• Flutter phase→spiracles rapidly open/close, O2 enters but CO2 keep building up

• Open spiracular phase→exchange O2, CO2 and H2O

What structures aid in Diffusion & Ventilation

• Air sacs

• body compression→thorax & abdomen

• rapid compression and expansion of trachea

• coordinated opening and closing of spiracles

• Hemolymph movements

Air sacs

• tracheal dilations

• assist in flight: increase buoyancy

• reservoir for oxygen

• increase tidal air flow

• decrease mass of flying insects

• distribution of cooler air

• Forms space for molting

• tympanic structures

• Helps to escape pupal case

Siphon (Terminal spiracle)

• helps insects to breathe in water

• suspends from water meniscus

• direct connection between atmosphere & spiracles in terminal respiratory siphon

• water repellent hairs at tip of siphon