Larval growth and foraging behavior of Aedes albopictus and Aedes japonicus. Deborah O Donnell Ph.D. Candidate Georgetown University VMCA 2/7/07

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1 Larval growth and foraging behavior of Aedes albopictus and Aedes japonicus Deborah O Donnell Ph.D. Candidate Georgetown University VMCA 2/7/07

2 Invasive Disease Vectors Introduction of new vector often followed by outbreak/ resurgence of disease Introduced to the New World: Ae. aegypti An. gambiae Ae. albopictus and Ae. japonicus

3 Aedes japonicus Ochlerotatus raised to genus (Reinert 2000) Controversial classification (Black 2004, Savage and Strickman 2004) We follow suggestions of Edman (2005) and Widdel et al. (in press) by using Aedes

4 Aedes albopictus Aedes japonicus Reported in 1985 From temperate Japan More anthropophilic Reported in 1998 From various sources Less anthropophilic

5 Invasion and range expansion of Ae. albopictus and Ae. japonicus Ae. japonicus spread into territory occupied by Ae. albopictus Differences in native, invasive ranges 1998 Ae. japonicus 1985 Ae. albopictus

6 Medical Significance Aedes albopictus: dengue, dengue hemorrhagic fever 22 arboviruses including eastern equine encephalitis Aedes japonicus: Japanese encephalitis eastern equine encephalitis La Crosse encephalitis St. Louis encephalitis Electron micrograph of the dengue virus (CDC)

7 Medical Significance West Nile virus Research focuses on Culex spp. Ae. albopictus Ae. japonicus can transmit WNV in the laboratory infected individuals discovered Potential bridge vectors Electron micrograph of the West Nile virus (CDC)

8 Background: ecology Larvae found in container habitats Foraging: microorganisms and dead particulate matter multiple feeding modes Resource use and foraging important

9 Foraging Efficiency and Behavior Predicted Ae. albopictus and Ae. japonicus would: (1) have different foraging efficiency (different larval growth) (2) have different foraging behavior (may explain differences in larval growth)

10 Experiments: Overview 1) Individual Foraging Efficiency 2) Cohort Foraging Efficiency 3) Foraging Behavior

11 Experiments 1) Individual Foraging Efficiency Ae. albopictus and Ae. japonicus larvae reared individually pupal mass and development time 2) Cohort Foraging Efficiency Ae. albopictus larvae in interspecific and intraspecific cohorts pupal mass and development time of 3) Foraging Behavior Behavior of individual Ae. albopictus and Ae. japonicus larvae Six different feeding environments

12 Experiments 1) Individual Foraging Efficiency Ae. albopictus and Ae. japonicus larvae reared individually pupal mass and development time 2) Cohort Foraging Efficiency Ae. albopictus larvae in intraspecific and interspecific cohorts pupal mass and development time 3) Foraging Behavior Behavior of individual Ae. albopictus and Ae. japonicus larvae Six different feeding environments

13 Experiments 1) Individual Foraging Efficiency Ae. albopictus and Ae. japonicus larvae reared individually pupal mass and development time 2) Cohort Foraging Efficiency Ae. albopictus larvae in interspecific and intraspecific cohorts pupal mass and development time of 3) Foraging Behavior Behavior of individual Ae. albopictus and Ae. japonicus larvae Six different feeding environments

14 Oviposition Traps Collected Ae. albopictus and Ae. japonicus eggs (Scott and Crans 2005)

15 Methods Overview Individual and Cohort Foraging Measured fitness indicators: (1) Development time (d) (related to generation time) (2) Pupal mass (mg) (related to fecundity)

16 (1) Individual Foraging Efficiency Ae. albopictus and Ae. japonicus larvae Reared individually in 24 well plates

17 3.2 Spp*** Sex*** Spp x Sex ns Pupal mass (mg) Development time (day)

18 (1) Results Individually reared Ae. japonicus had: higher pupal mass & shorter development time...compared to Ae. albopictus

19 (2) Cohort Foraging Efficiency Replicate cohorts of 30 larvae were established under two treatments: 1) Intraspecific foraging (Ae. albopictus only) 2) Interspecific foraging (Ae. albopictus & Ae. japonicus)

20 2.0 Trmt* Sex*** Trmt x Sex ns Pupal mass (mg) Development time (day)

21 (2) Results Presence of Ae. japonicus reduced larval growth of Ae. albopictus -Ae. albopictus had decreased pupal mass and increased development time (compared to Ae. albopictus only cohorts)

22 (3) Foraging Behavior Treatments: 1) Liquid Food 2) Plastic (Control) 3) Leaf 4) Plastic + Liquid Food 5) Leaf + Liquid Food 6) Leaf + Tire Water 1cmX5cm leaf 50 ml dh 2 0 small petri dish

23 Foraging Behavior: Methods 4 th instar larvae observed for 30 mins Instantaneous scan every 30 sec Position Surface, Leaf, Wall Activity Browsing, Filtering, Thrashing, Resting 30 reps/ treatment (15 of each species) 1cmX5cm leaf 50 ml dh 2 0

24 Behavior: Data Analysis Principal Components Analysis Create fewer principal component variables that capture original data s variation MANOVA Pairwise Contrasts Between species (within treatments)

25 PC1 and PC2 explain 82.2% of variation in data PC1 explains 61.2% browsing on leaf vs resting near surface or wall leaf browsing surface wall resting trashing PC2 explains 21.0% filtering vs resting near the surface or leaf/plastic filtering resting surface leaf wall browsing

26 (3) Results MANOVA of PC1 and PC2 Scores Behavior differs among treatments Species have different behavior within treatments Interaction exists b/w species and treatment species have different responses to changes in food treatments

27 Filtering 0.4 Pl Ae. albopictus Ae. japonicus PC 2 Resting, Surface, Leaf Liq Liq Pl Lf Lf Resting Surface, Wall PC 1 Browsing, Leaf

28 Filtering 0.4 Ae. albopictus Ae. japonicus PC Lf+TW Resting, Surface, Leaf Pl+Liq Pl+Liq Lf+Liq Lf+Liq Lf+TW Resting Surface, Wall PC 1 Browsing, Leaf

29 (3) Results Non- significant differences Ae. japonicus and Ae. albopictus did not differ: Liquid food treatment Plastic + liquid food treatment

30 (3) Results Significant differences Ae. japonicus was a more active forager: Plastic treatment Leaf treatment Leaf + liquid food treatment Leaf + tire water treatment

31 Conclusions Increased larval growth for Ae. japonicus More active foraging by Ae. japonicus Ae. albopictus larvae were less efficient at acquiring resources than Ae. japonicus Ae. japonicus invests more energy into foraging Ae. albopictus- more appropriate forager Ae. albopictus conserved energy w/o food Ae. albopictus found to be superior competitor to Ae. japonicus (J. Johnson, per. comm.)

32 Future Directions How does larval growth and foraging behavior relate to: competition, predation risk Immunity (energetic tradeoffs) Ability to transmit disease

33 Acknowledgements Field Site: Banks Auto Salvage Prince William County Armbruster Lab Georgetown University