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ENT 101 - Insect-Human Interactions > Module 2 - The Business of Being an Insect > Flashcards

Module 2 - The Business of Being an Insect Flashcards

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1
Q

What are the plates in an insect’s exoskeleton called?

A

Sclerites
- ventral side of each segment is the STERNUM
- dorsal side of each segment is the TERGUM
- the tergum on segments in the thoracic region is also called the NOTUM
- lateral region of each segment is the PLEURON

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2
Q

3 most important structures found on an insect head

A

antennae, eyes, mouthparts

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3
Q

Antennae
- What are they?
- What do they house?
- Are they the same for every insect?

A
  • pair of appendages on the head that come in a variety of shapes and sizes
  • house the sensory structures that are part of the PNS which are called sensilla; sensilla contain neurons that respond to specific chemical sin the air
  • different groups of insects have specialized antennae adapted to different enviro conditions and requirements; difference in morphology can be used to identify insect species
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4
Q

What are sensilla (sensory receptors on the antennae) used for?

A

smelling (olfaction) and in some rare cases detect taste, movement, moisture, air currents vibrations, heat

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5
Q

Photoreceptors

A
  • important sensory structure on the insect head
  • photoreceptors can include a pair of compound eyes, which are usually accompanied by up to 3 simple eyes known as ocelli
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6
Q

What are compound eyes composed of?

A

Multiple units known as OMMATIDIA
- each ommatidium can be considered an individual eye that contains a lens and a crystalline cone, which focus light onto photoreceptor and pigment cells
- images captured by individual ommatidia combine to provide the insect with 1 large comprehensive image

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7
Q

What do pigment cells do for photoreceptors (aka compound eyes)?

A

Adapt the photosensitivity of the eye to changing light conditions, and help to adjust the amount of light entering each individual ommatidium. Block light from passing btw ommatidia to increase the resolution of the image.

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8
Q

What are ocelli (simple eyes)? What is their primary role?

A
  • contain a single facet covered in transparent cuticle which can be curved into a lens that focuses light on an extended retina made up of sensory cells
  • appear as small swellings on a head, cannot pick up focused images
  • used to detect polarized light and changing light intensities
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9
Q

What is the main job of the mouthparts?

A

Acquire and ingest food
- many sensory sensilla are present on sections of the mouthparts to allow an insect to taste its food
- mouthparts are modified in multiple ways to enable insects to acquire specific foods

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10
Q

4 main structures of the mouthparts of an insect

A
  1. the labrum
  2. mandibles
  3. maxillae
  4. labium

*the sensory structures associated with the mouthparts are located on palps, with most insects having 2 pairs

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11
Q

Labrum

A

single structure that covers and protects other mouthparts

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12
Q

Mandibles

A

paired structures that act like sharp pinchers
- large, strong, and often serrated to cut, tear, and crush food
- can be used in aggressive behaviours

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13
Q

Maxillae

A

behind the mandibles, aid in cutting up food but are used mainly to manipulate and hold food in place for the mandibles to crush

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14
Q

Labium

A

below the maxillae, acts like a lower-lip, it can hold food in place and aid in food manipulation with the maxillae

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15
Q

Palps

A

associated with the maxillae and the labium house sensory receptors to smell and taste food

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16
Q

What mouthparts evolved in the earliest insects?

A
  • biting and chewing mouthparts; only solid foods can be effectively ingested, not liquids
  • overtime they’ve been modified in accordance with changes in diet specificity
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17
Q

What are the 4 main types of modified mouthparts used to exploit liquid food sources?

A
  1. piercing-sucking mouthparts
  2. siphoning mouthparts
  3. sponging mouthparts
  4. lapping mouthparts
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18
Q

Piercing-sucking mouthparts

A
  • used by insects to pierce animal or plant tissues to access nutritious fluids
  • modified into strong and pointed needle-like structures
  • salivary glands are also often present; may produce fluids that provide support around the mouthparts for plant feeding or act as anticoagulant in blood feeding insects
  • insects with these mouthparts have muscular sucking pumps in their heads
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19
Q

Siphoning mouthparts

A
  • long PROBOSICIS used to siphon liquids, such as nectar and water
  • proboscis made up of highly modified maxillae, that fuse or fit together to form a straw-like structure
  • only found in the order lepidoptera
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20
Q

Sponging mouthparts

A
  • consist of a sponging structure called a LABELLUM, which is covered in many tiny grooves that allow the uptake of liquid food by capillary action
  • some dipterans
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21
Q

Chewing-lapping mouthparts

A
  • unique to bees
  • lapping tongue important for pollen feeding
  • also have mandibles that can be used in nest-building, hive defense, and sometimes to cut through the bases of flowers to access nectar
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22
Q

The head is the…

A

sensory centre of the insect

23
Q

The thorax is…

A

the locomotory centre of the insect

24
Q

3 segments of the thorax

A
  1. Prothorax
    - leg pair
  2. Mesothorax
    - forewing location
    - leg pair
  3. Metathorax
    - hindwing location
    - leg pair
25
Q

Features and functions of the absomen

A

Most of the fxns are internal, such as digestion, as it contains most of the internal organs but there are some external fts to note.
- SPIRACLES are openings along the medial line of an insect’s thorax and abdomen and are involved in respiration
- External genitalia present towards the posterior
- CERCI are sensory appendages; sensilla on the surface of cerci of some insects detect air movement created by predators approaching from behind

26
Q

Male sex organ

A

Aedeagus
- normally retained within the body for protection
- major component is a tube-like organ called the penis through which sperm is transferred
- claspers allow the male to hold a mate during copulation, associated with the aedeagus of some species

27
Q

Female external reproductive organ

A

Ovipositor
- used to lay eggs
- some insects it is visible externally while in others it retracts when not laying eggs
- many have sensory structures that detect environmental cues so females can recognize optimal egg-laying sites

28
Q

Digestive system

A

Consists of a single complete tube, known as the ALIMENTARY CANAL
- canal has 2 openings; one for food ingestion and one for waste expulsion
- 3 regions: FOREGUT (stomodaeum), MIDGUT (mesenteron), and HINDGUT (proctodaeum)
- regions separated by valves and spincter muscles that control the movement of food
- each region has specialized fxns
- structure and modifications reflect the insect’s diet

29
Q

Foregut of the alimentary canal

A

where food is ingested and physically broken down, may also be a food storage site
- after food has been collected and manipulated by mouthparts it is passed into the mouth where digestion begins
- food is clumped into a bolus within the pharynx and the bolus passes throught he esophagus and into the crop (if present) for temp storage before being moved into the proventriculus
- Proventriculus is lined with rows of teeth to mechanically break down food; absent in some insects such as those with liquid diets

30
Q

Midgut of the alimentary canal

A

Where most digestion and absorption of nutrients occurs
- after passing through the proventriculus, food is passed into the midgut
- nutrient absorption maximized by having increased SA and enzyme secretion in outpockets known as GASTRIC CAECA
- nutrients from digested food selectively absorbed by the midgut epithelium and transported around the insect’s body in hemolymph
- no cuticular lining so this region of the canal is not shed with an insect’s moult; the PERITROPHIC MEMBRANE provides some protection and compartmentalizes the digestive process; it encapsulates the food bolus and is excreted along with solid waste
- peritrophic membrane can be secreted by cells in the anterior portion of the midgut or produced throughout the midgut, but must be secreted continously while the insect actively feeds; the membrane is absent in liquid feeders

31
Q

Hindgut of the alimentary canal

A

Where resorption of water, salts, and remaining nutrients occurs
- at the jxn btw the midgut and hindgut are the MALPIGHIAN TUBULES; noodle-like extensions of the hindgut that permeate the insect’s body cavity to remove nitrogenous waste and maintain osmoregulatory balance
- distal ends of tubules indiscriminately remove substances dissolved in hemolymph
- any water, sugars, or salts initially removed by tubules will then be resorbed at the proximal end of tubules or in the hindgut before excretion
- hindgut can be further divided into: ileum, colon, rectum
- like the foregut, the hindgut has a protective cuticular lining that must be replaced when the insect moults

32
Q

Osmoregulation

A

Maintaining the balance of H2O and solutes in the body; very important in ALL insects as desiccation is a risk
- terrestrial insects excrete nitrogenous wastes in a highly concentrated form called URIC ACID vs vertebrates that excrete urea

33
Q

Frass

A

what a fecal pellet is called when in the rectum; this is the material that remains in the hindgut after resorption is excreted from the rectum

34
Q

Fat body

A
  • a structure located outside of the alimentary canal that aids in digestion
  • structure and size of the fat body is variable but is essentially a network of fatty tissue located throughout the insect’s body
  • fxns: metabolism of large macromolecules, an essential storage organ from which the insect draw nutrients during non-feeding or strenuous parts of its life cycle
  • prominent in reproducing females, migrating insects and diapausing individuals, and juvenile holometabolous insects
35
Q

Alimentary Canal modifications

A

Structure varies with diet and the nutritional properties.

  1. Plant-feeding insects
    - wide, short, straight alimentary canals common to insects with solid diets
    - strong muscles in the gut to move the food bolus
    - specialized membranes that line the inner cavity to protect the gut from abrasions
    - short with little storage capacity bc large amounts of nutrient-poor food in the form of leaves and stems
  2. Animal-feeding insects
    - long alimentary canals with large storage capacities; diets are nutrient rich and need to be stored after consumption because these diets are available only intermittently
  3. Liquid-feeding insects
    - pharynx has prominent musculature to form a pump which is used to draw in liquid food
    - canal is long, narrow, and convoluted to maximize the SA of the gut available for nutrient absorption from a watery diet low in nutrients
    - gut may have other modifications to concentrate nutrients, such as a sort of bypass (filter chamber) that shunts excess water and sugar from the foregut to the hindgut leaving only necessary nutrients to be processed and absorbed in the midgut
36
Q

Symbionts

A

Internal and external microorganisms (bacteria, fungi, protists), hosted by insect bodies
- abundant in the alimentary canal
- can be passed between individuals by ingestion, or undergo vertical transmission from mother to offspring by transovarial transmission

37
Q

What do insect symbionts do?

A
  • aid in digestion, nutrient synthesis, and poison detoxification
    ex. digestion of cellulose is aided by symbionts, atmospheric nitrogen fixation, AA production, pheromone production
  • examples of toxins degraded in some insects by symbionts: terpenes, caffeine, nicotine, cocaine, and isothiocyanates
38
Q

What kind of circulatory system do insects and other arthropods have?

A

Open circulatory system
- hemolymph is not contained within blood vessels but within the HEMOCOEL, or body cavity
- all cells and tissues surrounded by barriers (basement membranes) to be kept separate from hemolymph

39
Q

Aside from water, what does the fluid of the hemolymph contain? What color is it?

A

Cells, inorganic ions, organic molecules (lipids, sugars, amino acids, proteins)

Varies in colour, although it is generally colourless and clear

Plasma is the liquid component and main constituent of the hemolymph
- plasma mediates the exchange of all chemicals including hormones, nutrients, and wastes, between insect tissues.

40
Q

What is the main blood sugar of many insects that is a nutrient distributed by the hemolymph?

A

Trehalose
- a disaccharide composed of 2 glucose molecules
- can also be found in other invertebrates as well as bacteria, fungi, and plants

41
Q

What does the hemolymph NOT do?

A
  • does not transport O2; no hemoglobin (some exceptions)
  • in general the circulatory and respiratory systems of insects are separate
42
Q

Hemocytes

A
  • the other main constituents of the hemolymph
  • nucleated cells with many fxns; major component of the insect immune system
  • 1 fxn is phagocytosis
  • multiple can act collectively to encapsulate larger foreign materials or parasites
  • also involved in the coagulation of hemolymph when the integument is wounded
  • can store and distribute nutrients
43
Q

How is hemolymph moved throughout the insect body?

A

By muscle contractions, particularly by the DORSAL VESSEL = a tube that runs along the back of the insect, pumping hemolymph anteriorly.

The body cavity is also separated by a DORSAL DIAPHRAGM and VENTRAL DIAPHRAGM which help guide the flow of hemolymph

To ensure continuous flow is maintained, there are pulsatile organs located at the bases of appendages which pump hemolymph through the associated appendages.

44
Q

How does hemolymph enter the dorsal vessel?

A

Through OSTIA
- one-way valves allow hemolymph to enter the dorsal vessel, where waves of muscle contractions push the hemolymph anteriorly, and out of the vessel at the insect’s head

45
Q

What is the respiratory system of insects comprised of?

A

A network of cuticle-lined tubes called TRACHEAE. They permeate the insect’s body and allow gas exchange.
- tracheae are usually reinforced with spiral thickenings that prevent them from collapsing but still allow flexibility
- lining is shed with each mouth
- tracheae brand into smaller tubes called TRACHEOLES; abundant around tissues w/ high O2 demand; sometimes embedded in tissues

46
Q

What connect the tracheae to the outside environment?

A

Openings in the body wall called SPIRACLES
- laterally along the thorax and abdomen
- have valves that open only during gas exchange, and may also have filters that cover the openings to help limit exposure to harmful particles or microorganisms, in addition to reducing water loss

47
Q

What does the size of the tracheal system vary with?

A
  • varies btw insect species, as well as with an insect’s body volume and developmental stage
  • highly active = extensive system
  • architecture is predetermined but the growth is plastic allowing for an autonomous response to oxygen deprived tissues
48
Q

Air sacs

A

Tracheae are modified in some insects to form air sacs = regions of the tracheal network where the tracheae are enlarged and the ringed thickenings that usually provide support are reduced or lost to allow the air sacs to stretch. Act as a reservoir to increase ventilation. Also, can allow for some growth within an exoskeleton and sometimes sound production.

49
Q

How is gas exchange accomplished in insects?

A
  • mostly by diffusion through the tracheae, however ventilation is also used to increase the efficiency of gas exchange
  • efficiency of gas exchange in insects is a limiting factor on overall body size because diffusion is the principal method of gas exchange, and diffusion is only effective over short distances = proportionally larger tracheal network in large insects when compared to small insects
50
Q

What is a byproduct of gas exchange?

A

Loss of water
- net movement of water vapour is outward
- terrestrial insects must balance the need for gas exchange with the risk of water loss

51
Q

How has the tracheal system been adapted to terrestrial vs aquatic insects?

A

Terrestrial: open tracheal system in which the tracheae open to the enviro through the spiracles

Aquatic: most have a closed tracheal system, in which the spiracles are absent or sealed

52
Q

What must aquatic insects with an open tracheal system do?

A

Must visit the surface periodically for gas exchange or carry an air bubble called a “gas gill” with them.
- gas gills are a film or bubble of air that covers the spiracles and allows gas exchange to occur within the water

53
Q

What must aquatic insects with a closed tracheal system do?

A
  • some can perform gas exchange simply by diffusion across the cuticle
  • many other have evolved tracheal GILLS = a fine network of branched tracheoles which are contained in highly variable internal or external structures specialized for gas exchange

ENT 101 - Insect-Human Interactions (12 decks)

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