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Effect of larval and adult diet on desiccation resistance of marula fruit fly, Ceratitis cosyra
(Walker) (Diptera: Tephritidae)
Mnguni Sandiso 10358626Supervisors: Dr C.W. Weldon & Prof S.W. Nicolson
C.W Weldon C.W Weldon
Introduction• Water availability
– survival, distribution & fitness
• Small size of insects is a challenge
• Water acquisition– food consumption, drinking, atmospheric H2O & by-
product
A. Coetzer
Physiological adaptations
• Physiological adaptations– water loss rates, water storage & dehydration tolerance
• Role of heamolymph– reservoir
• Nutrition role• Importance of metabolic reserves
– Larval feeding– Adult feeding
Study species
• Ceratitis cosyra (Walker)• Diptera: Tephritidae• Fly of economic importance • Serious pest
– Wide distribution– Many plant families
Dr C.W Weldon www.dermis.lnC.W Weldon
Hypothesis
Manipulation of larval and adult diet results in increased nutrient content thus enhances desiccation resistance
A. Coetzer A. Coetzer
Materials and Methods
• Fly colonies and manipulation• Larval diet
– (high = 8% yeast) (low = 1% yeast)
• Adult diet– (high = sugar + YH) (low = sugar)
YH = hydrolysed yeast (source of amino acids, lipids & micronutrients)
Dr C.W Weldon
Assays
• Initial mass, dry mass, water content & dehydration tolerance assays
• Desiccation resistance assay
At 0 days and 10 days after emergence
A. Coetzer A. Coetzer
Data analysis
• Generalised Linear Modelling– Independent variable
Larval and adult diet
– Dependent variable Initial mass, dry mass, water content & dehydration tolerance
• Cox Proportional Hazards Desiccation resistanceAll data analysed in Statistica (version 11)
Initial mass - unfed fliesHigh yeast leads to more body mass
SEX female SEX male
low yeast high yeast
LARVAL DIET
6.0
6.5
7.0
7.5
8.0
8.5
9.0
9.5
10.0
10.5
11.0
INIT
IAL
MA
SS
(mg)
Water content - unfed flieshigh initial mass leads to more body water content
SEX female SEX male
low yeast high yeast
LARVAL DIET
5.4
5.5
5.6
5.7
5.8
5.9
6.0
WAT
ER
CO
NTE
NT
Desiccation - unfed flies
LARVAL DIET
LON
GE
VIT
Y (h
ours
)
SEX: femaleSEX: male
high yeast low yeast50
60
70
80
90
100
110
120
high initial mass and water content leads to low desiccation resistance
Initial mass - fed flies
high protein leads to more body mass, irrespective of larval diet
SEX female SEX maleLARVA DIET: low yeast
ADULT DIET:sugar
sugar + YH6
7
8
9
10
11
12
13
INIT
IAL
MA
SS
(mg)
LARVA DIET: high yeast
ADULT DIET:sugar
sugar + YH
Water content - fed flieswater content varied depending on larval diet, exhibiting sex-specific differences
SEX female SEX maleLARVA DIET: low yeast
ADULT DIET:sugar
sugar + YH5.4
5.5
5.6
5.7
5.8
5.9
6.0
6.1
6.2
WAT
ER
CO
NTE
NT
LARVA DIET: high yeast
ADULT DIET:sugar
sugar + YH
Desiccation resistance - fed flies
ADULT DIET
LON
GE
VIT
Y (h
ours
)
LARVAL DIET: low yeast, SEX: femaleLARVAL DIET: low yeast, SEX: maleLARVAL DIET: high yeast, SEX: femaleLARVAL DIET: high yeast, SEX: male
sugar sugar + YH28
30
32
34
36
38
40
42
44
46
48
50
52
54
56
58
high resistance when reared in low yeast larval diet
Discussion• Larval and adult diet both affect desiccation resistance • Larval diet plays a greater role than adult diet• Adult diet affected desiccation in a sex-specific way• Larvae with high initial mass had high water content but low
desiccation resistance• Water content is not responsible for desiccation resistance (similar
patterns) in adult flies reared in low yeast larval diet • High initial mass could be causing high water loss rates• Prior exposure to stress environment could be key• Females (larger in size) had greater desiccation resistance than
males and performed better when they fed in low protein, irrespective of the larval diet
Conclusion
Desiccation resistance largely depends on larval diet.Adult diet leads to sex-specific differences.Adult females thrive in low protein while adult males thrive in both high and low protein.The findings were irrespective whether adult flies were reared in high or low yeast as larvae.
Acknowledgements • Dr Aruna Manrakhan (Citrus Research International)• Ezette Du Rand (Department of Biochemistry)• Tshidi Hlalele (Department of Zoology and Entomology)• Andre Coetzer (Photographer)
Dr C.W Weldon Dr C.W Weldon
Thank you…