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