SubP. Uniramia: C. Insecta

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SubP. Uniramia C. Insecta

• Circulation
• tubular ? in pericardial cavity creates
  peristaltic wave
• moves hemolymph forward via dorsal aorta
• accessory pulsatory pumps hemolymph into
  wings/legs
• body mvmts helps
• hemolymph plasma amebocytes
• little O2 transport
• hemoglobin in hemolymph func.
  in O2
  transport in aquatic immature
  sp. in
  low O2 environments

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SubP. Uniramia C. Insecta

• Gas exchange
• problem
• exchanging gas but limit water loss
• tracheal system used for gas exchange
• branched network of tubes throughout body
• tracheal trunks open to outside via spiracles
• 2 pair on thorax, 78 on abdomen
• simple hole or w/ valves to ? water loss
• filters dust
• tracheae composed of 1 layer of cells lined
  w/ cuticle
• spiral thickenings of cuticle (taenidia)
  prevent
  tracheal collapse
• tracheae branch into tiny fluid-filled
  
  tubules (tracheoles)
• reach individual cells

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SubP. Uniramia C. Insecta

• Excretion/water balance
• Malpighian tubules rectal glands
• blind ends of tubules float freely in hemocoel
• bathed w/ hemolymph
• K actively secreted into tubules
• other solutes (urate) follow
• 1 waste product is uric acid
• K CO2 ? KHCO3 reabsorbed
• pH ?, uric acid precipitates
• rectal glands reabsorb Cl/Na/H2O
• wastes pass out
• honeydew
• arid vs. aquatic sp.

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SubP. Uniramia C. Insecta

• Nervous system
• similar to larger crustaceans
• fusion of ganglia
• some have giant fiber system
• neurosecretory cells in brain func. to control
  molting/metamorphosis

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SubP. Uniramia C. Insecta

• Sense organs
• keen sensory perception
• mechanoreception
• touch/pressure/vibration picked up by sensilla
• sensillum single hair-like seta or complex
  organ w/ nerve cell(s)
• mostly distributed over antennae/legs/body
• auditory reception
• tympanal organs detect airborne sounds
• tympanic membrane
• Orthoptera/Homoptera/Lepidoptera
• organs in legs detect vibrations of substrate
• other senses
• very sensitive to temp.
• detect humidity/proprioception/gravity

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SubP. Uniramia C. Insecta

• visual reception
• 2 types of eyes
• simple, compound
• most have 3 ocelli on head (light
  intensity/daylength)
• cmpd eyes contain 1000s ommatidia
• similar to crustaceans
• can see simultaneously in almost all directions
• image is fuzzy
• flying insects have higher flicker-fusion rate
• distinguish 200300 flashes per sec
• bee can see UV light
• cannot detect shades of red
• butterflies see red

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SubP. Uniramia C. Insecta

• chemoreception
• taste/smell
• bundles of sensory cell processes in sensory pits
  on mouthparts/antennae/legs
• detect odors for several km
• feeding/mating/habitat selection/host-parasite
  relationships mediated via chemical senses
• sensitive to CO2
• pheromones

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SubP. Uniramia C. Insecta

• Neuromuscular coordination
• active thus require excellent neuromuscular
  coordination
• cross-striated muscles
• strength of muscle related to cross-sectional
  area
• flea can jump 100x body length by storing energy
  in elastic resilin protein
• cocked
• compressed resilin pads

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WARNING

• The following slides may contain sexually
  explicit material.

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SubP. Uniramia C. Insecta

• Reproduction
• dioecious
• parthenogenesis common
• internal fertilization
• deposit sperm in vagina
• nutrients also passed to ? via spermatophore
• sexual attraction
• ? moths secrete pheromone
• fireflies use flashes
• use sounds/color signals/courtship behaviors
• ? may only mate 1x
• store sperm to fertilize eggs throughout life
• lay few eggs care for young or lay ? eggs
• butterflies/moths must lay eggs on
  
  host plant for caterpillars survive
• wasps must locate specific host

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SubP. Uniramia C. Insecta

• Metamorphosis and growth
• various degrees of change
• most insects change form after hatching from egg
• each stage btwn molts instar
• insects develop wings during last stage
• useful in reproduction

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SubP. Uniramia C. Insecta

• Holometabolous (complete) metamorphosis
• 88 insects
• separates physiology of larval growth, pupal
  differentiation and adult reproduction phases
  (each stage looks very different)
• larvae/adults often live in completely different
  environments
• ? competition
• stages egg ? larva ? pupa ? adult
• pupa overwinter inside cocoon/chrysalis

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SubP. Uniramia C. Insecta

• Hemimetabolous (gradual/incomplete) metamorphosis
  
• immature looks like adult
• grasshoppers/cicadas/mantids/true
  bugs/dragonflies
• young nymphs
• stages egg ? nymph (several instars) ? adult
• Ametabolous (direct) development
• young similar to adults except size/sexual
  maturation
• silverfish/springtails
• stages egg ? juveniles ? adult

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SubP. Uniramia C. Insecta

• Physiology of metamorphosis
• regulated by hormones
• organs involved
• brain/ecdysial glands/corpora cardiaca/corpora
  allata
• produces brain hormone (prothoracicotropic
  hormone - PTTH)
• neurosecretory cells send axons to corpora
  cardiaca
• stores/release PTTH
• PTTH carried via hemolymph
  to prothoracic
  gland
• produces molting hormone (ecdysone)
• triggers ecdysis
• prothoracic glands degenerate in
  adults

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SubP. Uniramia C. Insecta

• larval molting continues as long as juvenile
  hormone (neotenine) produced
• produced by corpora allata
• corpora allata releases less and less juvenile
  hormone w/ time
• when juvenile hormone is low, larva ? pupa
• cessation of juvenile hormone production in pupa
  leads to last molt (adult)
• in adults, corpora allata active again in normal
  egg production

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SubP. Uniramia C. Insecta

• Hibernation winter dormancy
• Estivation summer dormancy
• Any stage may remain dormant to survive adverse
  conditions
• allows synchronization w/ environment
• Diapause period of dormancy in annual life
  cycle that is independent of conditions
• genetically determined
• triggered by environmental cues (e.g. daylength)
• always occurs at end of active growth stage
• then ready for another molt
• many larvae enter diapause until spring in spite
  of mild temp.

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SubP. Uniramia C. Insecta

• Defense
• protective coloration/shape (crypsis)
• warning coloration (aposematic coloration)
• mimicry
• exoskeleton
• repulsive odors/tastes
• aggression
• chemicals (digested/sprayed)

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SubP. Uniramia C. Insecta

• Communication
• respond to many environmental stimuli
• responses governed by physiological state
  nerve pathways
• behaviors are complex sequences of responses
• behavior is innate but some involve simple
  learning
• pheromones
• secreted by 1 indiv. to affect behavior of
  another
• func.
• attract opposite sex
• trigger aggregation
• fend off aggression and mark trails
• recognize nestmates
• signal an alarm
• used to trap insects to monitor populations

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SubP. Uniramia C. Insecta

• sound production/reception
• func.
• warning devices
• advertisement of territory
• courtship songs
• tactile communication
• tapping/stroking/grasping/antennae touching
• bioluminescence
• fireflies
• some sp ? mimic another species flash pattern
• attract ? and then eat them