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Entomology > Excretion and Water Balance > Flashcards

Excretion and Water Balance Flashcards

1
Q

Insects, like most animals, must Maintain and eliminate what?

A

Maintain a reasonably constant blood composition and total water content for cell viability and must eliminate toxic wastes

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2
Q

Where can Euryhaline mosquito larvae survive and how?

A

In everything from fresh water to 300% sea water and alkaline salt lakes
- Drink their own body weight every few hours to harvest dilute food from pond sediments (Filter feeders)

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3
Q

Where do mealworms live, what do they eat and what kind of excrement do they produce?

A
  • Lives in dry environment, eats dry food and produces dry excrement
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4
Q

Desert locusts, what do they eat and what kind of excrement do they produce?

A
  • consume own weight in succulent plants and produce moist excreta unless they are starved in which case they produce dry excreta
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5
Q

What is the general nature of the excretory process? why do they take place?

A
  1. Eliminate most blood solutes non-selectively; takes place in the malpighian tubules
  2. Selectively reabsorb useful solutes; takes place in the hindgut (mostly)
  3. Actively secrete certain toxins (malpighian tubules
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6
Q

why would insects feed on toxic plants?

A
  • nutrution
  • defense
  • synthesis
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7
Q

What happens during dehydration for an insect?

A

-low blood pressure and a dramatic drop in blood volume during dehydration

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8
Q

Why are the effects not especially detrimental?

A

Hemolymph is not used for gas exchange

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9
Q

What is a consequence of of dehydration?

A

Formation of primary urine in insects cannot occur by pressure driven filtration

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10
Q

What do most insects actively secrete?

A

K+ (with Cl- as anion) forming KCl rich urine

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11
Q

What does an insects KCl rich urine cause?

A

A large concentration gradient between the hemolymph and malpighian tubule lumen for diffusion of all other blood solutes

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12
Q

What is the main excretory organ in insects?

A

Malpighian tubules

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13
Q

What is the structure of malpighian tubules?

A

Blind-ended tubules composed of a single layer of epithelial cells (3 cells when seen in a cross-section.
- can be differentiated histologically along their length with up to 4 distinct sections

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14
Q

Which insects lack malpighian tubules?

A

Aphids and collembola

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15
Q

What are Malpighian tubules?

A

A slowly operating system for secretion of primary urine

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16
Q

Why are all the nutrients excreted and then reabsorbed as needed?

A

It is energetically more favorable cause it is easier to reabsorb needed molecules passively than to actively excrete all unneeded ones

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17
Q

What is the main excretory product?

A

Uric acid

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18
Q

What is the main function of the excretory system?

A

Removed nitrogenous (metabolic) wastes

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19
Q

Which takes longer to completely filter their blood, humans or insects?

A

Insects

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20
Q

What do mapighian tubules secrete?

A

sugars, amino acids, water, KCl, toxins and nitrogenous wastes

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21
Q

Where is primary urine secreted?

A

from the Malpighian tubules to the hind gut

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22
Q

Where is a major source of water balance in the insect (where most water is reabsorbed)?

A

Rectum

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23
Q

What is reabsorbed in the hindgut?

A

sugars, amino acids and ions (to maintain osmolity of the hemolymph)

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24
Q

What does reabsorption of water in the rectum facilitate?

A

K+ secretion in the malpighian tubules

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25
Q

Where are the distal ends of the malpighian tubules fused?

A

the rectal wall

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26
Q

What does diuretic hormone do?

A
  • stimulates diuresis

- Promotes water loss

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27
Q

What does antidiuretic hormone do?

A
  • Prevents water loss by promoting fluid reabsorption in the hindgut
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28
Q

What is diuretic hormone stimulated by?

A

Distention of the gut

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29
Q

What is anti diuretic hormone stimulated by?

A

Dehydration

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30
Q

What is Rhodnius?

A

Hemolymph from bloodfed bug is injected into an unfed bug which stimulates diuresis

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31
Q

What does cauterization of mNSC cells in the brain cause?

A

Causes insect to swell (no diuresis)

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32
Q

What does an injection of mNSC cause?

A

Diuresis

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33
Q

What are diurestic hormones?

A

group of neuropeptides ranging in size

- more potent form found in the corpora cardiaca; form produced in the brain is a precursor

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34
Q

What are some endocrine factors that increase absorption of water?

A
  • antidiuretic hormone
  • Homogenates of corpora cardiaca or ventral ganglioa stimulate up to 5-fold increase in reabsorption in the ileum of locusts
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35
Q

What secretes proline and where is it reabsorbed?

A

secreted in the malpighian tubules and reabsorbed in the rectum

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36
Q

What is proline utilized as?

A

an energy source to drive active transport in metabolically active rectum tissue

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37
Q

Where is the proline secreted by the malpighian tubules completely utilized?

A

by the mitochondria of the hindgut which have a specific proline carrier

38
Q

What is feeding governed by?

A

a central excitatory state which is affected by sensory input

39
Q

What are external stimuli?

A

Olfaction, gustation

40
Q

What are internal stimuli?

A

Crop volume, nutrient concentrations in hemolymph

41
Q

What factors can the responsiveness of sensilla vary with?

A
  1. state of hunger ( time since last meal)
  2. Nutritional state
  3. Neurohormone levels
  4. Nonassociative learning
42
Q

where does control of feeding reside?

A

the sub-oesophageal ganglion

43
Q

What is the sub-oesophageal ganglion?

A

fusion of the mandibular, maxillary and labial ganglia; considered part of the brain

44
Q

What separate factors are involved in each step of feeding?

A
  1. Biting (=initiation)
  2. Continuation
  3. Termination
45
Q

Feeding mechanisms almost always depend on what?

A

some direct stimulus from the food to the Sensilla

46
Q

How does feeding work in Blowflies?

A

Stimulation of the tarsal sensilla by sugars etc. Leads to extension of the proboscis; sensilla on the labellum then determine if feeding proceeds

47
Q

How does feeding work in Schistocerca?

A

Tarsal, maxillary, and labial palp sensila all need to be stimulated to initiate biting; after the first bite, quality of the food is monitored by cibarial receptors

48
Q

Are more or less receptors needed for specialized feeders?

A

Fewer are needed

49
Q

What are phagostimulants?

A

Stimulus necessary for initiation and often continuation of feeding

50
Q

What are phagodeterrents?

A

Stimulants that can inhibit feeding even in the presence of stimulants

51
Q

What does acceptance of food and feeding rate usually result from?

A

The ratio or balance of stimulants and deterrents in the food

52
Q

Do stimulants or deterrents change the amount of time it takes for an insect to start eating?

A

no

53
Q

What is effected by the presence of stimulants or deterrents in food?

A

total amount of food eaten

54
Q

What regulates the termination of feeding?

A
  • Thought based on the decay of the excitatory state through:
  • Chemosensory adaptation or habituation
  • Increased foregut volume detected through stretch receptors
  • Negative feedback from nutrients or hormonal factors in the hemolymph
55
Q

Which mouthparts are salivary glands especially important for?

A

piercing/sucking mouthparts

56
Q

What does the saliva of blood feeders include?

A
  • Local anesthetics
  • Vasodialators
  • Anticoagulants
57
Q

What is contained within the saliva of sucking plant feeders?

A

Digestive enzymes such as amylase or invertase

58
Q

What does aphid saliva contain? Why?

A

Pectinases - facilitate penetration of the stylets through plant tissues to the vascular tissues (Phloem)

59
Q

What can enzyme secretion in the midgut be regulated by?

A
  1. Secretagogue
  2. Neural Stimulation
  3. Hormonal stimulation
60
Q

What is Secretagogue?

A

An enzyme stimulating substance in food

61
Q

What are the neural Stimulators that signal the presence of food in the midgut?

A

Stretch receptors

62
Q

How does hormonal secretion regulate secretion of enzymes?

A

Hormones respond to nutritional state of the insect

63
Q

What is the rate of digestion determined by?

A

the rate of degradation of polysaccharides to monosaccharides

64
Q

What is the Paunch?

A

An Anaerobic region of the hindgut

65
Q

What does an insect need for proper nutrition? (6)

A
  1. 10 essential amino acids
  2. Cyclitols
  3. Fat-soluble vitamins
  4. Water-soluble vitamins
  5. Free fatty acids
  6. Sterols
66
Q

Which amino acid is the most important for larval growth?

A

phenylalanine

67
Q

What are cyclitols needed for?

A

Membrane synthesis

68
Q

What is vitamin A complex used for?

A

vision

69
Q

What happens if a lepidoperan has a defficiency in free fatty acids?

A

Many cannot pupate or have wing deformities as adults

70
Q

Can insects synthesize sterols?

A

no

71
Q

How do plant feeding insects obtain sterols?

A

Modify phytosterols to cholesterol which is essential for synthesis of ecdysteroids, etc.

72
Q

What are sterols used for?

A

molting hormones

73
Q

What is the relative growth rate of an insect?

A

= Weight gained per day/ average larval weight

74
Q

What is the relative consumption rate of an insect?

A

= Mg ingested per day/ average larval weight

75
Q

What is the efficiency of conversion of ingested food?

A

= Weight mg gained/ mg food ingested x 100

76
Q

What is the Efficiency of Conversion of digested food?

A

= Weight mg gained/(mg ingested-mg frass(poop)) x 100

77
Q

What is the Approximate Digestibility of an insect?

A

= (mg ingested - mg frass(poop))/mg ingested x 100

78
Q

What is the calculation for metabolic cost of an insect?

A

1- ECD

79
Q

Which insects have the highest RGR? Lowest?

A 
Highest = Forb-feeding homoptera
Lowest = Aquatic detrivores
80
Q

Which insects have the highest/lowest RCR?

A 
Highest = Tree feeders
Lowest = Predatory insects
81
Q

Which insects have the highest/lowest ECI %?

A 
Highest = Seed-feeding hemiptera
Lowest = Aquatic detrivores
82
Q

Which insects have the highest/lowest ECD %?

A 
Highest = Seed-feeding hemiptera
Lowest = Ants
83
Q

Which insects have the highest/lowest AD %?

A 
Highest = Forb-feeding coleoptera
Lowest = Dung-feeding insects
84
Q

What is a major requirement for optimal growth?

A

Nitrogen (Amino acids, proteins)

85
Q

What are RGR and ECI positively correlated with?

A

% Dietary N

86
Q

Why do insects have a specific need for Amino N?

A

Cause exoskeleton is composed of up to 20% aa derivatives

87
Q

What is Phenylalanine important for?

A

Formation of the integument

88
Q

What is water a major influencer of?

A

Larval growth

89
Q

Can insects partially compensate for reduced food quality?

A

yes

90
Q

Which is more efficient, Holometobolous insects or hemimetabolous insects? Why?

A

Holometabolous insects because most of food they eat goes to the integument

91
Q

Why do self selectors of diet grow slower?

A

They waste time and energy switching foods

Entomology (14 decks)

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