1. Effect of larval and adult diet on desiccation
resistance of marula fruit fly, Ceratitis cosyra
(Walker) (Diptera: Tephritidae)
Mnguni Sandiso 10358626
Supervisors: Dr C.W. Weldon & Prof S.W. Nicolson
C.W Weldon C.W Weldon
2. Introduction
• Water availability
– survival, distribution & fitness
• Small size of insects is a challenge
• Water acquisition
– food consumption, drinking, atmospheric H2O & by-
product
A. Coetzer
3. 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
4. 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
5. Hypothesis
Manipulation of larval and adult diet
results in increased nutrient content thus
enhances desiccation resistance
A. Coetzer A. Coetzer
7. 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
8. 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 resistance
All data analysed in Statistica (version 11)
9. Initial mass - unfed flies
High 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
INITIALMASS(mg)
10. Water content - unfed flies
high 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
WATERCONTENT
11. Desiccation - unfed flies
LARVAL DIET
LONGEVITY(hours)
SEX: female
SEX: male
high yeast low yeast
50
60
70
80
90
100
110
120
high initial
mass and
water content
leads to low
desiccation
resistance
12. 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 + YH
6
7
8
9
10
11
12
13
INITIALMASS(mg)
LARVA DIET: high yeast
ADULT DIET:
sugar
sugar + YH
13. Water content - fed flies
water
content
varied
depending
on larval
diet,
exhibiting
sex-specific
differences
SEX
female
SEX
maleLARVA DIET: low yeast
ADULT DIET:
sugar
sugar + YH
5.4
5.5
5.6
5.7
5.8
5.9
6.0
6.1
6.2
WATERCONTENT
LARVA DIET: high yeast
ADULT DIET:
sugar
sugar + YH
14. Desiccation resistance - fed flies
ADULT DIET
LONGEVITY(hours)
LARVAL DIET: low yeast,
SEX: female
LARVAL DIET: low yeast,
SEX: male
LARVAL DIET: high yeast,
SEX: female
LARVAL DIET: high yeast,
SEX: male
sugar sugar + YH
28
30
32
34
36
38
40
42
44
46
48
50
52
54
56
58
high
resistance
when
reared in
low yeast
larval diet
15. 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
16. 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.
17. 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
