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…