Module 3 - The Business of Being an Insect II Flashcards
1
Q
What does a nervous system do?
A
Detects, transmits, and interprets info from the outside world
2
Q
What are one of the reasons that insects have become such a successful and diverse group?
A
Sophistication of their nervous system gives them a keen awareness of the external environment
3
Q
What is a neuron?
A
The foundation of the nervous system. It is a special type of cell which receives info from the external enviro and sends info to tissues
4
Q
What are the 3 key parts of the neuron?
A
- Dendrite
- receives info from enviro or other neurons - Cell body
- signal transmitted through the cell body, this is where the nucleus is found - Axon
- signal continues along from the cell body along the axon towards another neuron or a target cell tissue
5
Q
In what form do neurons transmit information?
A
Electrical impulses btw other neurons or to and from cells and tissues. Impulses travel in waves mediated by the electrochemical gradient neurons maintain across their cell membranes.
6
Q
What is the action potential of a neuron?
A
Wave-like change in membrane potential along the neuron
7
Q
What are the 3 roles neurons can perform in the transmission of info within the nervous system?
A
- Sensory neurons
- sense info from the external enviro and pass it along to the CNS - Motor neurons
- transmit signals from the CNS to the muscles - Interneurons
- create a ‘bridge’ btw any two or more neurons so that info can pass btw cells quickly and efficiently
8
Q
What is the space between the axon of the transmitting neuron and the dendrite of the receiving neuron?
A
a SYNAPSE sometimes called a synaptic cleft
9
Q
Within the synapse, what are the chemical messengers that pass the signal between neurons or between a neuron and a target tissue?
A
Neurotransmitters
- can either excite or inhibit the transmission of a signal
10
Q
What is an important excitatory neurotransmitter in insects? What does it affect?
A
Acetylcholine
- an organic chemical released by neurons that stimulates other neurons
- affects muscular movement, learning, and memory
11
Q
What are the two components of the nervous system?
A
- Peripheral NS
- neurons housed in sensory receptors throughout the body which detect and transmit signals from stimuli in the surrounding enviro - Central CS
- brain and ventral nerve cord
12
Q
What are neurons that pick up external stimuli found distributed across the insect body called?
A
Sensory receptors
- antennae, compound eyes, and mouthparts all contain an abundance
13
Q
What is the trichoid sensillum?
A
A common sensory receptor found in insects
- has a single hair-like structure called a seta that is associated with one or more neurons
- modified for mechanoreception or chemoreception
14
Q
What is ‘mechanoreception’?
A
When the seta of the trichoid sensillum is stimulated by movement, an AP is generated in the neuron within the sensillum, which is transmitted to the CNS. This allows mechanoreceptors to inform insects about physical cues from the enviro.
15
Q
What is chemoreception?
A
The ability to perceive chemical stimuli. Many critical decisions are dependent upon chemoreception. Chemosensitive sensilla have one or more tiny pores along the seta that allow molecules of liquids and gases to enter. The chemical compounds dissolve in a fluid contained within the seta and then bind to receptors on the sensory neuron, which transmits a signal to the CNS.
16
Q
What are the 2 types of trichoid sensilla that can detect chemical stimuli?
A
- olfactory chemoreceptors
- contact chemoreceptors
17
Q
Where is the nerve cord in insects?
A
lies along the ventral side of the body
18
Q
What does the CNS do?
A
Receives signals from the PNS and controls behaviour
19
Q
Within the CNS, nerve cells are bundled into interconnected masses called what?
A
Ganglia
- located along the length of the ventral nerve cord and joined by connectives
20
Q
What is the insect brain comprised of?
A
3 distinct pairs of ganglia within the head
21
Q
What do mushroom bodies in the anterior brain allow for?
A
some capacity for memory retention and learning in insects, especially from olfactory cues.
- well developed in social insects which require complex communication
22
Q
What do the second pair of ganglia in the insect brain receive signals fom?
A
Receive signals mainly from the receptors on the antennae.
- olfactory signals are process here, and interneurons transmit these signals to higher brain centres to influence subsequent behaviour
23
Q
What does the third part of the brain receive information from?
A
Directly from the labrum and foregut, and from the rest of the body.
24
Q
What is the subesophageal ganglion?
A
Found posterior to the brain, they are a fourth pair of ganglia. This acts as a bridge between the insect brain and the rest of the CNS. It also connects with the muscles that control the movement of the insect mouthparts.
25
What does the nervous system rely on to communicate complex information?
Hormones and neurohormones
26
How are hormones different than neurotransmitters?
Hormones move through the insect body via the hemolymph, rather than directly between neruons in the nervous system.
27
Where are insect hormones and neurohormones produced and released?
By a special type of neuron called a NEUROSECRETORY CELL
- located throughout nervous system but there is a greater concentration in the brain
28
What are neurohormones?
Hormones produced by neurosecretory cells that promote further hormone production in other non-neural tissues, such as the endocrine glands
29
What are ecdysteroids and juvenile hormone examples of?
Hormones regulated by neurohormones
- ecdysteroids play a major role in the process of molting
- neurohormones produced and released by the corpora cardiaca stimulate the production and release of exdysteroids by the prothoracic glands
- JH is produced directly by the corpora allata
30
What do insecticides target?
the insect nervous system of pest species; without a functioning nervous system an insect cannot survive
31
What are 2 groups of neurotoxic intesticides?
1. axonic poison
2. synaptic poisons
32
What does the neurotoxic insecticide, axonic poison do?
Inhibits the ability of a neuron to transmit an AP along the axon
- insects will exhibit tremors and have a general loss of control of motor fxns
33
What is a well-known axonic poison?
DDT
34
What does the neurotoxic insecticide, synaptic poison, do?
They affect the synapses btw neurons within the nervous system of the affect insect. Synaptic poisons cause rapid
nerve firing in neurons
- cause uncontrollable tremors, restlessness, paralysis, death
- many target acetylcholine or the enzyme that break it down since it is the most abundant
35
Insects exhibit internal fertilization, when does this occur?
Occurs when the sperm and egg unite inside the body of the female, which requires that the individuals find each other and interact
- ensures a high rate of fertilization
- evolved in response to a terrestrial lifestyle where external conditions are too harsh for gamete survival
36
What is multimodal communication? When it is used?
Step 1 of reproduction is finding a partner. Communication between sexes occurs in a variety of ways and many use multiple types of cues in multimodal communication
- visual, auditory, pheromones (most common)
37
What is a pheromone?
A chemical signal that when received alters the behaviour or physiology of conspecifics
- many insects signal their mating availability with sex pheromones; female often releases pheromones and male locates her but for bumblebees it is the opposite
38
What allows individuals of the same species to communicate amidst other chemical cues in the enviro?
Chemical composition of pheromones is very species specific
39
For insects such as cicadas who communicate to potential mates using auditory cues, why is this dangerous?
- can potentially attract parasitoids and predators
40
For insects that use auditory cues to attract a mate, what do females judge attractiveness of a male on?
Based on his song, they use this as an indicator of his suitability as a mate
- female listens for the lowest and deepest chirps which are associated with larger individuals
41
What cue is used particularly by butterflies and fireflies to find mates?
Visual cues
42
What do the visual cues of a firefly look like?
Flying males emit patterns of flashing light with a pattern unique to each species. A receptive female flashes a specific pattern in response to indicate her sex and receptivity.
43
After a pair of insects have located one another (visual, auditory, pheromones) what is the next step?
For a male to attract his potential mate through the art of courtship
- must prove himself worthy of the female's investment
- dances, displays, aphrodisiacs, gifts
- sometimes the male's appearance plays a part too ("the bigger the better")
44
What are aphrodisiacs?
courtship pheromones used by some male insects to stimulate sexual receptivity in females
- also provide an indication of the amount of protective alkaloid chemicals a male has sequestered that will be passed along to the female with his sperm; alkaloids applied to eggs for protection
45
What is multi-modal communication?
When an insect uses more than one mode of communication
ex. butterflies; use chemical and visual cues when seeking and choosing a mate
46
What is a nuptial gift?
Another courtship behaviour found in insects.
- often a food item that the male gives the female that she uses to assess the fitness and health of a male and nutrients for egg production
47
In many members of the order Orthoptera (grasshoppers and crickets) in what kind of package are nuptial gifts offered in?
As a package known as a spermatophylax
- contains nutrients and a packet of sperm called a SPERMATOPHORE
48
What are 3 examples of a nuptial gift?
- food, captured prey, the male himself
49
What is sexual cannibalism?
When in some cases, the male becomes his own nuptial gift.
- body is consumed for nourishment
- evolved more often in species in which individuals within a population are spaced far apart with a low likelihood of encountering one another
50
What is nature's way of compensating for the energy used by the female during reproduction?
males are the ones that put energy and effort into courtship
51
Where is the reproductive system of female insects housed?
the abdomen
52
What is the reproductive system of female insects designed for?
egg production and to receive, store, and manipulate sperm
53
What does the female reproductive system contain?
- ovaries
- ovarioles
- oviduct
- spermathecal gland
- spermatheca
- accessory glands
- genital chamber
54
Where are eggs produced?
ovarioles
55
What is each egg within the ovary loaded with and encased in?
Loaded with YOLK and other nutrients and is encased in a protective shell called the CHORION
56
What happens during the process of OOGENESIS?
New eggs are produced within each ovariole. After oogenesis, eggs are released from the ovariole and travel down the oviducts into the genital chamber.
57
Where are eggs fertilized by sperm?
Genital chamber
58
What does the spermatheca of the female reproductive tract allow for?
sperm to be stored for long periods of time inside the female's body
- supplied with nutrients from the spermathecal gland
59
What do the accessory glands of the female repro tract do/produce?
After an egg has been fertilized and travels through the female's genital chamber, it may be covered by secretions from these glands.
- accessory glands produce materials such as lubricants and glues to help stick the eggs to each other and onto the surface where they will be laid
60
When does the egg begin embryonic development?
After fertilization
61
What does the yolk provide the egg with?
Nutrients so that the embryo can complete development outside of the female
62
What is the male reproductive system specialized for?
The production, storage and dissemination of sperm
63
What are the 5 parts of the male repro tract?
1. Testes
2. Vas deferens
3. Seminal vesicle
4. Accessory gland
5. Intromittent organ
64
What are the paired testes responsible for?
The production of sperm; sperm develop withing the tubes in the testes and once fully mature travel down from the testes through the Vas Deferens
65
What is the fxn of the seminal vesicles of the male repro tract?
Storage chamber for sperm until mating occurs
66
What do the accessory glands of the male repro system do?
Supply the gametes with additional fluid
- lubrication for the sperm entering into the female's oviduct
- ejaculatory fluids help protect and nourish sperm
Also produce substances offered as nuptial gifts
May even produce specific chemicals that influence a female's receptivity
67
What is a sperm plug?
In some insects, used by males to physically prevent their mates from mating with other males.
- composed of a large amount of ejaculatory fluid that hardens to block other males' access to the female's reproductive tract OR the male's own copulatory organ (the aedeagus) breaks off and lodges within the female
68
In primitive insect groups, what do males synthesize to protect the sperm while it is transferred to the female's genital tract?
Spermatophores
- some insects have lost spermatophore and pass on free-swimming sperm in ejaculatory fluids while others package sperm-containing spermatophores with protein-rich accessory gland secretions into a SPERMATOPHYLAX
69
What is traumatic insemination?
Used by bed bugs to transfer sperm, the male pierces the female's abdominal cuticle to create a new opening
70
What are 3 ways that males transfer sperm to a female?
1. spermatophores
2. free-swimming sperm in ejaculatory fluids
3. spermatophylax
71
What is sexual conflict?
Wherein the female and male have conflicting strategies or interests concerning repro
- common in insects!!
72
What are factors of copulation that differentially affect the sexes?
frequency, duration, mode of mating
73
What is oviparity?
Displayed by most insects, this is when the female deposits fertilized eggs onto an external surface, like a plant
- embryos in the eggs are in an early stage of development when eggs are exposed to outside worlds
74
What is oviposition?
The process by which the egg passes from the female's genital opening to the outside environment
75
Oviparous females produce eggs with what?
With a nutrient-rick yolk to provide the developing embryo with essential proteins, CHOs, lipids, and slats
76
For most insects that exhibit oviparity, do they care for their offspring once eggs have been laid?
NO! This is why eggs are covered in a tough protective layer, the chorion
- in some species parental care does occur
77
What is ovoviviparity?
A reproductive strategy in which some female insects carry eggs inside their bodies throughout embryonic development
- embryos still receive nutrients from yolk
- released once eggs are ready to hatch
- provides extra protection for the young
- evolved in insects that rely on ephemeral resources only available for a short period of time
78
What is viviparity?
A reproductive strategy in which embryos continue to develop within the female after hatching from the egg
- developing offspring are not provided with nutrients from a yolk instead they are fed from their mother's accessory gland secretions, hemolymph supplements, and sometimes tissues comparable to placentas
- provides protection for offspring but restricts the number of yound
79
What is asexual reproduction?
Occurs when offspring are produced from a single female or hermaphroditic organism without the involvement of a male
- prevalent in the insect world
80
What is parthenogenesis?
A reproductive strategy whereby unfertilized eggs develop into embryos without the involvement of a male, usually resulting in genetic clones of the mother
- occurs in may stick insect sin the order Phasmatodea
- in some cases meiosis still occurs, in other cases it does not
81
What is holocyclic?
Type of reproduction with periods of asexual reproduction interspersed with sexual reproduction
82
What is haplodiploidy?
A type of sex determination mechanism that results from parthenogenesis
- male hymenopterans are produced from unfertilized eggs
- females develop from diploid fertilized eggs
83
What is polyembryony?
An odd mode of reproduction in endoparasitic insects where a single egg splits into multiple embryos
- reduced exposure to threats because she only needs to oviposit once to produce a large number of offspring
- embryos obtain energy from the host they parasitise
84
How do insects with reproductively-mature juveniles produce offspring?
Paedogenesis
- in many cases these juveniles never reach an adult form
- adult females only produce during specific conditions, while most repro occurs in female larvae
- not limited to asexual reproduction
-
85
What is hermaphroditism?
Another peculiar form of repro in insects when both male and female reproductive structures are present in a single individual
- can fertilize themselves
- rare
- the entire population are functional hermaphrodites
86
What are the 3 peculiar forms of reproduction in insects?
1. polyembryony
2. paedogenesis
3. hermaphroditism
87
What can we ensure when we interfere with insect mating success?
- we can ensure that the population size of the next generation of pests will be low, and their impacts reduced
- achieved by: mating disruption and sterile insect technique
88
89
What are 3 strange reproductive strategies used by some insects?
1. Polyembryony
2. Paedogenesis
3. Hermaphroditism
90
How do insects with reproductively-mature juveniles produce offspring?
Paedogenesis
- adult females only produce during specific conditions while most repro occurs in female larvae
- repro system matures faster than the rest of the body so that eggs are ready to be laid during the larval stage or sometimes the pupal stage
- not limited to asexual reproduction
91
What is hermaphroditism?
A peculiar form of repro where both male and female repro structures are present in a single individual who can fertilise themself
- sexual repro btw individuals occurs in this strategy as well
92
What are the two ways we can interfere with mating success?
1. mating disruption
2. sterile insect technique
93
What is mating disruption?
Exploits the pheromone-based mating-finding behaviours employed by many insects, especially within the order Lepidoptera.
- reduces successful fertilization, oviposition, pest population density, and pest-induced damage
- synthetic pheromones; high cost = used to control pests in high-value crops or for severe problems without other feasible solutions
- effective to control invasive pest species since their populations are low
-environmentally friendly and very specific to targeted insect
94
How do pest population densities play a large role in determining the success of a mating disruption program?
- at low densities the program works well to interfere with male response to rare females spread throughout the habitat
- at high pop densities a male is more likely to find a female without pheromone cues simply bc they have a higher change of encouter
95
How does sterile insect technique work?
Aims to reduce pest populations by diluting the population with a large number of sterile individuals that are not able to produce offspring
- to achieve this, the target pest must be mass reared which requires a large amount of time and money
- high cost = used against high risk pests of high value crops
- goal is to eradicate pests from an infested region, not just reduce pop
- high sterile-to-wild pop ratio must be maintained over multiple yrs
- requires collaboration btw gov bodies, industry partners, landowners
