Flashcards in Devo Lect 21 - Insect Meta. Deck (25):
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Ametabolous
Pronymph to adult doesn’t require much change. Not really metamorphosis.
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Hemimetabolous
Pronymph goes through nymph stages before adult which is significantly different (ie wings)
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Holometabolous
Very significant changes from larva to adult
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Ecdysis and function
Ecdysis = molting. Exoskeleton is basically thick ECM limits growth of larva, needs to molt in order to continue growing. Accomplished by increasing movements etc.
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Instar
One larval stage. Holometabolous organisms have several instars before metamorphosis
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Metamorphic molt
Last molt before larva becomes pupa
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Imaginal molt
Molt from pupa to adult (butterfly)
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How many stages does Drosophila have?
3 larval instars, then pupa then adult for a totally of 4 molts
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Ecdysone description
Hormone involved in molting; steroid based so it can go through membranes and turn on genes needed
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Ecdysone production
cyclical; peaks just before a molt, then drops and hits low at molt
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Polytene chromosomes and ecdysone
Puffs show where ecdysone turns genes on
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Process of molting
Apolysis, new cuticle produced, old cuticle digested, ecdysis, expansion, darkening and hardening, maturing
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Apolysis
Glands in epidermis start secreting enzymes that create separation b/w old cuticle and epidermis
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Expansion
Old cuticle is flexible, needs to be larger so the larva can grow. It will take in water or air to stretch it out
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Eclusion
Another word for imaginal molt
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Instars
Period in between losing an exoskeleton
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Imaginal disks
Epidermal thickenings which will become antenae, limbs etc; these cells are determined; can be studied in vitro (and they produce structures)
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Cause of metamorphosis experiment
Decapitate first instar larva, connect to head of adult, undergoes metamorphosis
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Corpus allatum
Piece of insect brain which secretes JH, experiments show that it keeps larva from doing metamorphosis
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JH
juvenile hormone, from corpus allatum. Prevents metamorphosis, not sure what it targets exactly
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JH signaling loop
JH from corpus allatum; neurosecretory cells release prothoracicotropic hormone, causes prothoracic gland to release ecdysone, molting occurs. No JH in adult.
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Kr-h1
Kruppel homolog-1; activated by JH injection; if blocked by RNAi, then metamorphosis happens early
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Mosquitoes
Holometabolous; females suck blood for nutrient
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Problems with insecticides
Used to manage insects; problems are killing all insects, or toxicity on other species
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