Lecture 14

Question 1

Other modes of reproduction

Answer 1

-Parthenogenesis- nonfertilized eggs 
 Three types: Thelytoky(female), Arrhentoky(male), Deuterotoky(male and female)
-Paedogenesis (larval and pupal)
-Hermaphrodism: ovatestis
-Endosymbionts: Wolbachia

Question 2

Parthenogenesis

Answer 2

• Sexual reproduction involves 1n+1n to 2n(sperm+egg=diploid zygote)
• Can also reproduce asexually, without mating, and this is partenogenesis
• These species have females producing offspring without sperm/males
• Advantage in stable environment and abundant food resource

Question 3

Arrgenotoky

Answer 3

• MALES
• Type of parthenogenesis where all members of order (hymenoptera: ants, bees, wasps) and some thrips and scale insects
• Females are diploid 2n and males are haploids 1n. Females can control release of sperm and can lay a fertilized egg(female) or a unfertilized eggs (male)
• This regulation of sex is important for structure and social ants, bees, wasps

Question 4

Thelytoky

Answer 4

• FEMALES
• found in aphids, scale insects and cockroaches, and stick insects, and weevils
• These insects have females producing 2n eggs that are exactly like the mother
• Clones herself through parthenogenesis, large amount of offspring in short time
• Advantage of parthenogenesis species live in stable environment and exploits food source

Question 5

Pseudo-arrhenotoky

Answer 5

• Known as PGE
• Males develop from fertilized eggs but parental gene lost in somatic cells and not passed to offspring
• Beetles, mealy bugs, and scale insects
• equivalent to haploiddiploids arrhenotoky where males are haploid and develop from unfertilized eggs and certain diploid arrhenotoky where males fail to pass half of chromosome from mom

Question 6

Polyembrony

Answer 6

• Condition where 2 or more embryos devlop from one egg, TWINS
• Hymenoptera; Copidosoma, has parasite of a cutworm laying an egg which turns to 200 individuals
• Fall into two classes, hymenoptera nd strepsiptera
• From one egg, thousands of offspring can be made

Question 7

Paedogenesis

Answer 7

• Form of reproduction by larvae, without fertilzation
• Distinct from neotenic reproduction (no fertilization) and eventual maturation or metamorphosis of parent organism in adult form

Question 8

Parental Care

Answer 8

• Not common in insect world, but giant waterbug female glues eggs to male’s back
• Female taking care of eggs, young, earwig good example

Question 9

Metamorphosis

Answer 9

Each molt= a bit larger

It can also change physically depending on type of metamorphosis (3 types)

Question 10

Ametabolous

Answer 10

• Insects have little to no structural change as they grow. Immatures are called young, physically similar to adults except size and sexual maturity
• No external manifestation of age or reproductive state
• egg—>nymph—>adult; the same execept size
• NO WINGS
• ex. silverfish
• Also known as no metamorphosis
• Same habitats and habits

Question 11

Hemimetabolous

Answer 11

• Gradual changes, immatures called nymphs or naiads
• Maturation of wings, sex organs, and other adult structures occur in small steps from molt to molt
• Wings completely absent in first instar, then 2nd-3rd instar they are little stub, and grow until full developed
• Changes are usually visible externally, adults retain same features though
• INCOMPLETE metamorphosis
• Terrestrial insects have nymphs resembling the adults except the adults have wings. Similar habits and habitats
• Aquatic insects will have naiads distinct from adults, closely related but differ in habitats. Feed on different things
• Egg—-> nymph/naiad—–> adult (there is stage between young and adult, SUBIMAGO, may look fully developed but is sexually immature)

Question 12

Holometabolous

Answer 12

• Insects have immature forms (larva) very different from adults
• Larvae are feeding machines just so they can grow
• Larger in size each molt but don’t develop adult characteristics
• Fully grown larvae molt to immobile pupa stage so they can go under complete transition
• All unneeded parts digested and replaced with adult structures. Adults usually have wings (dispersal and reproduction)
• Egg—>larva—>pupa—> adult
• larvae do not look like adults
• DO NOT have similar habitats or habits
• COMPLETE metamorphosis

Question 13

Advantage to Complete Metamorphosis

Answer 13

• Reduced competition between immatures and adults
• Adults feed on new source of food
• Adults have different habitats

Question 14

3 forms of larvae

Answer 14

• Polypod larvae: (many leg)- 3 pair of thoracic legs and 5 pairs of abdominal legs (caterpillar)
• Oligo larvae: well developed thoracic legs, no abdominal legs (beetles)
• Apod larvae: (no leg)- no legs mostly flies, maggot

Question 15

Pupal types of holometabolous insects

Answer 15

• Obtect: Known as Chrysalis, enclosed with silken cocoon. Appendages held tightly like a shell. Examples are butterflies and moths
• Exarate: All the appendages are free in this type, and very visable. Examples are beetles and lacewings
• Coarctate: Known as puparium. Body is encased in hard exoskeleton of the next to last larval instar. Examples are flies.

Question 16

Steps to molting

Answer 16

• Molting is the most important aspect of metmorphosis
  1) Increase activity of epidermal cells
  2) These cells seperate from old cuticle (APOLYSIS)
  3) Epidermal cells now secrete molting fluid but its inactive
  4) Now cells will secrete new epicuticle. Seperates the cells from molting fluid
  5) Now that is sepearte, the fluid is active and it will break down the old endocuticle
  6) Old endocuticle is absorbed by epidermal cells. 90% recycled for new endocuticle
  7) Exocuticle and epucuticle not broken down by fluid
  8) New cuticle is wrinkled under the old one and the insect must expand
  9) The exdysial sutures form where there is no exocuticle. When endocuticle is dissolved, it weakens these sutures
  10) Insect now takes in air or pumps blood to blow up. This splits old cuticle from sutures and the insect can emerge from old skin (Ecdysis)
  11) After exdysis, insect is light and soft, over time it will darken and harden
  12) Eats left over cuticle for nutrients

Question 17

Summary of Molting

Answer 17

1) Apolysis- seperation of old exoskelton from epidermis
2) Secretion of inactive molting fluid
3) Cuticulin later produced for new exoskeleton
4) Activation of molting fluid
5) Digest/Absorb old endocuticle
6) Epidermis secretes new procuticle
7) Ecdysis occurs, where old exoskeleton is shed and epicuticle
8) Expansion of new integument
9) Tanning occurs of new exocuticle

Question 18

What causes this molting process?

Answer 18

There are hormones

Question 19

What is PTTH?

Answer 19

Prothoracicotrophic hormone is a brain hormone that stimulates that production of ecdysone(molting hormone) by prothoracic glands in insect larvae

Question 20

Summary of types of hormones

Answer 20

• Neurosecretory cells produce neurosecretion
• Prothoracic glands produce ecdysone
• Corpora allata produce juvenile hormones
• Corpo cardiaca produce Adipokinetic hormones and stores/release brain hormones
• Midgut endocrine cells produce peptides
• Epitracheal glands produce ecdysis triggering hormone (Eclosion) in lepidoptera

Question 21

WHOLE PROCESS (picture)

Answer 21

First the brain sends message to the prothoracic gland, sends hormone(PPTH) to stimulate the production of Ecdysone. That way the prothoracic gland will produce ecdysone (molting hormone). There is another part, corpus allatum, that makes the juvenile hormone which is important for immature stages. Pictures shows how the juvenile hormones contribute to the larval-larval molting stages and larval-pupa molting stage. Ecdysteriod is important for every molting stage.

Question 22

What are the two crucial hormones for molting/development?

Answer 22

Ecdysone and juvenile hormones

Question 23

What are instar and stadium?

Answer 23

• Instar is the form between the molt

- Stadium is the time between the molts

Question 24

Voltanism

Answer 24

• # Generations per year
• univoltine: 1 generation
• bivoltine: 2 generations
• multivoltine: many generations

Question 25

Unstable Environmental Conditions

Answer 25

Aestivation: Summer Diapause: Winter Quiescence is slowed development which resumes in favorable conditions Diapause is slowed development/physiological change, resumes with stimuli - Cues for diapause= photoperiod, temperature, food quality, moisture, ph, chemicals, O2, urea, 2 degree plant compounds

Question 26

Environmental extremes

Answer 26

- Cold - Heat - Aridity - Migration

Question 27

Environmental Effects on Development

Answer 27

- Temperature: Poikilothermic and physiological time/degree days - degree days is the amount of heat required over time for complete insect development - 1 degree day= 1 degree over 13.3 C for 24 hours - Since insects are poikilothermic, their development depends on temperature - High temperature=fast development because biochemical reactions will occur frequent and rapidly - Diffusion rates for substrates and enzymes also increase which causes greater formation of these complexes