L4 Abdomen

Question 1

How many segments in the abdomen?

Answer 1

primitively 11, Modern is difficult to distinguish segments, can usually see 5-7

Question 2

What appendages are homologous to jointed walking legs of metameric ancestor?

Answer 2

Styles

Question 3

describe cerci

Answer 3

On 11th segment, not homologous to ancestral jointed walking legs, not segmented.
Earwigs have enlarged cerci to form pincers for male/male competition

Question 4

What surface allows for gas exchange?

Answer 4

Abdominal gills/gill plates
in aquatic juveniles
v thin cuticle

Question 5

describe prolegs

Answer 5

in juveniles especially lepidoptera and hymenoptera
not jointed but are extensions of the cuticle.
Moves by changes of internal blood pressure
Ring of hooks on foot end

Question 6

What are the main features of the abdomen adapted to?

Answer 6

egg laying and reproduction

Gonopore on segment 7 of abdomen

Question 7

What are 2 types of ovipositor?

Answer 7

Appendicular ovipositor

Substitional ovipositor

Question 8

Describe the apendicular ovipositor

Answer 8

Plate structures behind gonopore form a tube, deposits eggs onto the substrate
very extravagant in parasitoids.

Question 9

Describe the Substitutional ovipositor

Answer 9

lost plates, changes in blood turgor causes it to extend out of body. Flexible system, most terminal segments are collapsed and held inside.

Question 10

what genital openings do insects have?

Answer 10

Primitive - only 1, gonopore, mating and egg laying occurs here. on 7th abdominal segment.
Advances - gonopore for mating, ovipore for egg laying on 11th segment.

Question 11

What is the adeagus?

Answer 11

Penis. Complex structure is a mechanism of speciation

Question 12

5 parts of the male reproductive system

Answer 12

1. testes
2. Vas deferens, joins testes to Seminal vesicle
3. seminal vesicle stores sperm
4. Accessory gland - secretions coat sperm to form spermatophore
5. Adeagus - with claspers/spikes to aid mating

Question 13

Female reproductive system

Answer 13

1. Ovaries - composed of several tubes, no.hugely variable [ovarioles], meiosis occurs at the tip, produvcing haploid oocytes.
2. Lateral oviduct and comon oviduct join 2 ovaries to gonopore.
3. Spermotheca - 1-3, stores sperm
4. Accessory gland - Secreted coating over batches of eggs. produces ootheca, a small pod filled with eggs,protected for embryogenesis.

Question 14

Development of oocyte as it travels down the follicle

Answer 14

Haploid oocyte passes down ovariole
follicle cells laid around it
Nurse cells and Yolk develop inside oocyte
Yolk grows and egg increases in size. Yolk eventually fills egg

Question 15

How is the yolk formed?

Answer 15

Vitellogenesis - synthesis from the fat body. From fat body. passed through blood to ovary, deposited in oocyte by nurse cells.

Question 16

What does the fat body do?

Answer 16

Adipocyte cells store glycogen and triglycerides as an energy reserve.
Dynamic tissue, multiple metabolic functions. One function is to store and release energy in response to insect’s energy demands.

Question 17

Autogeneous/Anautogeneous/Facultatively anautogeneous

Answer 17

Autogeneous insects don’t require a protein meal to start maturing eggs
Anautogeneous insects do require a protein meal. this can be a major limitation.
Facultatively anautogeneous- depends on how successful juvenile stages are.

Question 18

fancy name for egg shell production

Answer 18

choriogenesis

consists of a vitelline membrane and chorion

Question 19

What happens in ovulation?

Answer 19

Upon ovulation, egg moves out of ovariole into lateral oviduct.
Can be stimulated by mating, mechanical pressure, or the presence of a suitable ovulation site - sometimes if a suitable place is not found, yolk is reabsorbed back into body.

Question 20

Describe the steps involved in fertilisation

Answer 20

• sperm stored in spermatheca after mating
• female gets enough sperm for all eggs in lifetime, males may also damage reproductive tract to prevent other males mating with her.
• Fertilisation occurs as eggs pass down common oviduct past spermatheca
• sperm pass through micropiles [holes in egg shell]

Question 21

How are eggs adapted to being underwater?

Answer 21

Aeropyles - thin layer of air trapped around egg surface to allow gas exchange for a while.

Question 22

Oviparous

Ovoviviparous

Answer 22

Oviposit - lay eggs, most insects are oviparous

Larviposit - eggs hatch in common oviduct and live larvae produced. Gives them a competitive advantage.

Question 23

Example of adenotrophic viviparity

Answer 23

tsetse flies - release one egg at a time, which hatches in the common oviduct and develops through all the larval forms. Nourished by secretions of accessory gland. When final larvae deposited, it weighs as much as the fly.

Question 24

Describe haplodiploidy

Answer 24

Female has choice over whether to fertilize eggs as they pass down the common oviduct.
Fertilised = Female, diploid
Unfertilised = Male, haploid
Sperm are identical, since males are haploid. Insects have a higher degree of relatedness between sisters so have more complex social systems than other animals.

Question 25

What is Sperm precedence and how does it affect male competition?

Answer 25

The last sperm into the spermatheca is the one to fertilise the egg.
Causes males to try and prevent females mating again, by destroying the oviduct or ‘mate guarding’.
eg Female yellow dung beetles lay eggs in the centre of a cow pat, so larger males compete to be in the centre so are the last ones to mate.
Many males have structures on the genetalia to scrape out previous sperm from female.

Question 26

Give an example of secondary genetalia

Answer 26

Damselflies - males form ‘wheel’ with female

Sperm transferred from primary to secondary genetalia on male then into female.

Question 27

How can age of insects be determined?

Answer 27

If temp is known, can work out how many previous eggs have passed through the ovaries by analysing yolk deposition.
Because the oocyte pops out of follicle, can see remnants of follicle cells at the tip of descending oocyte.