Insect Development Flashcards
What are the three different types of development?
Ametabolous, Hemimetabolous, Holometabolous
What type of wing development corresponds to which type of development?
Apterygota = Ametabolous, Exopterygote = Hemimetabolous, Endopterygota = Holometabolous
What orders are ametabolous?
Collembola, Protura, Diplura, Archeognatha and Zygentoma
Which Orders are Hemimetabolous?
Hemiptera, Mantodea, Blattodea, Grylloblattodea, Phasmatodea, Plecoptera, Odonata, Ephemeroptera, Mantophasmatodea.
What are the characteristics of ametabolous insects?
Primitively wingless, indeterminate moulting, monomorphic
What are the characteristics of hemimetabolous insects?
Primitively winged, wings develop externally, wings develop from wing buds, have a nymph juvenile stage, determinate moulting, dimorphic life cycle
What are the characteristics of holometabolous insects?
Primitively winged, wings develop internally, wings develop from imaginal discs, have a larval juvenile, determinate moulting, trimorphic life cycle (with pupa)
What are the three layers of an initial egg?
oocyte nucleus, periplasm and yolk
What makes up the egg shell and when is it made?
Egg shell is deposited while in ovary, made up of vitelline envelope and chorion (wax layer, endochorion, exochorion)
What are the three types of holes in the chorion?
Micropyle, Hydropyle, Aeropyle
What is a Micropyle useful for?
Useful for sperm entry into the egg
Whats the purpose of hydropyles?
Used for water uptake across whole egg surface
What the purpose of aeropyles?
gas exchange with the outside world
When does meiosis complete in the egg?
After fertilization for sexual repro, during ovulation or oviposition for parthenogenesis
What happens after the sperm penetrates the egg?
Mieotic divisions complete, haploid oocyte nucleus fuses with sperm nucleus in the interior of the cell
What is embryogenesis?
After fertilization, before eclosion involves uptake of water and oxygen
What are the steps of embryogenesis?
Nucleus divides, and migrate to the periphery of the egg, nuclei form one-cell thick layer around the periphery = blastoderm, Blastoderm goes thorugh regional differentiation forms germ anlage region of columnar cells, Grastrulation envagination of the germ anlage develops into germ band, germ band develops into ventral body (migration is called katatrepsis) Segmentation of the ventral body with appendage formation, Dorsal Closure, Grows over yolk and fuses dorsal and lateral body develop.
What is hatching called?
Eclosion, bugs swallow fluid and air along with muscular contraction to break free
What is moulting?
periodic formation of new cuticle and subsequent shedding of the old cuticle
What is apolysis?
The stage where the epidermis separates from the cuticle of previous stage
What is ecdysis?
The process of casting off the old cuticle at the end of moulting
What is the pharate condition?
The period in between apolysis and ecdysis
What is an instar?
Growth stage of immature between two successive moults
What is a Stadium?
The time between 2 successive moults (length of instar)
What is an imago?
The adult stage of the insect
What part of the cuticle is sclerotized?
The exocuticle
How many steps are in the moulting process?
14
What are the initial steps of ecdysis?
The insect becomes quiet, the Corpora Cardiaca releases PTTH which triggers the prothoracic glands to release ecdysone which stimulates cell division in epidermis.
What happens in moulting after ecdysone is released?
Stimulates cell divisions in epidermis, epidermis separates from old cuticle, space between old cuticle and epidermis is called the exuvial space, epidermis fills the exuvial space with inactive moulting gel, Epidermis begins to secrete new epicuticle.
What is in moulting gel?
Chitinases, proteinases and aminopeptidases
What happens when the new epicuticle is deposited?
The new epicuticle stabilizes and the mouting gel is activated to dissolve the old endocuticle recycled for the new procuticle, ecdysis triggering hormone from epitracheal glands, eclosion hormone from neurosecretory cells and Crustacean cardioactive peptides trigger moulting behaviour.
What is moulting behaviour?
Insect swallows air, contracts abdominal muscles, and forces blood into the head and thorax, causing expansion and collapse
What follows moulting behaviour in moulting?
Old cuticle breaks at performed lines of weakness and insect crawls out (ecdysis), New cuticle is soft and extensible expands new cuticle to final size, Release of bursicon from neurosecretory cells causes outer part of procuticle to sclerotize forming new exocuticle, wax layer is deposited on new epicuticle, cement layer is deposited on surface endocuticle continues to be deposited during intermoult period.
What dictates what stage the insect will go into to?
Juvenile hormone suppresses the expression of adult features.
When are there spikes in juvenile hormone?
There are spikes around the time of ecdysis, spikes get smaller as the insect ages.
Which scientist experimentally demonstrated the hormone sequence of insects?
Vincent Brian Wigglesworth
What are imaginal discs?
groups of undifferentiated cells invaginated below the larval epidermis correspond to particular body parts.
What is the main role of the imago stage?
Reproduction and often dispersal
What is the subimago stage?
Stage in the ephemeroptera order that is winged without reproductive organs.
What does rate of insect development depend on?
The quality and amount of food, Seasonal patterns of temperature and rainfall, environmental signals photoperiod
What is voltinism?
The number of generations of a species in a year?
What are the different categories of voltinism?
Univoltine (1 a year), Bivoltine (2 a year), Multivoltine (more than 2 a year), Semivoltine (less than 1 a year)
What is diapause?
Stage of suspended morphological development or suspended reproduction that is genetically controlled and triggered by environmental conditions, can occur at any stage
What is diapause used for?
winter survival in temperate regions and drought survival in the tropics
What environmental cues trigger diapause?
Insects have a photosensitive period where they are aware of how long the days run, if the proper conditions are met then they will enter dispause later on.
What are the two types of diapause?
developmental diapause and reproductive diapause, and obligate diapause and facultative diapause.
What is obligate diapause?
Diapause that can occur without the need of environmental cues, typical of univoltine insects
What is facultative diapause?
diapause that is dictated by environmental cues, commmon in divoltine and multivoltine species.
What type of stimuli can induce diapause?
Photoperiod, Dry season, Lower moisture, temperature and food, once induced it will occur regardless of environmental conditions
What is a Long-day insect?
an insect that doesnt undergo diapuase under long days
What are short-day insects?
no diapause under short-days
How do insects prepare for diapause?
Build up lipid reserves in fat body, reduces watera nd increase glycerol, slight muscles may degenerate, seek out shelter, more wax into epicuticle.
What triggers the end of diapause?
Return of favourable conditions triggers the end of diapause
Which moth has the longest diapause?
Yucca moth for up to 30 years
