Effect of temperature and nutrition on the development and inter specific relationship of Aedes aegypti and Ae. albopictus (Diptera: Culicidae) Thahsin Farjana and Nobuko Tuno Laboratory of Ecology, Kanazawa University, Japan

Background More than one-third of the world’s population living in areas at risk for dengue transmission (CDC-2010) Dengue Map Province or local level   Country level Areas of ongoing transmission risk    Map courtesy: CDC-Health Map collaboration, 2010

artificial containers Artificial containers Two competent vectors for dengue and DHF Aedes aegypti indoor and outdoors: artificial containers 2. Aedes albopictus urban Artificial containers Natural containers Rural Sub-urban Vegetated urban

Aedes aegypti: Global distribution Ae. aegypti infested areas with dengue epidemic activity Ae. aegypti infested areas Map courtesy: CDC dengue map, 2006

Ae. albopictus: Global distribution Map Courtesy: Landcare Research, 2004

geographic distribution of vector borne diseases. Global climate change Regional temperature and photoperiod may affect the distribution of these two species (Hawley, 1988) Vegetation/Detritus type may affect the outcomes of inter specific competition in sympatric areas (Murrell & Juliano, 2008)

Interspecies competition Our questions: Combined effect of temperature & nutrition ?????? Larval growth Interspecies competition

Materials and Methods Laboratory stocks: Aedes aegypti Tanzania strain (Mosi, Tanzania) Ae. albopictus Japan strain (Nagasaki, Japan) Adults maintenance; 25±1°C, humidity (70-90%), 14L/10D photoperiod 3% sucrose solution Mouse blood (once per week).

Manipulated conditions: 1. Temperature (20, 25, 30, 35°C) 2. Nutrition (Poor vs Rich) Poor: 0.05 mg for 1st and 2nd instars 0.1 mg for 3rd and 4th instars Rich: 0.2 mg for 1st and 2nd instars 0.5 mg for 3rd and 4th instars 200 ml water + 20 larvae Species size Single species: 20 larvae x 5 replicates Mixed species: Ae. aegypti 10: Ae. albopictus 10 x 10 replicates

Larval developments, survival, molting and pupation were checked daily Wing length of emergent adults were measured (Van Den Heuvel, 1963). Measured parameters: Mortality at developmental stages Development period from 1st instars to adult (♀ and ♂) Wing length of adults (♀ and ♂) Interspecies competition among 2 species

Per capita performance, Index I With Modification from Livdahl and Sugihara 1984 Ln(1/N0)(∑ wx3) I = ∑x wx3 / ∑ wx3 No, is the initial number of larvae in an experimental treatment wₓ, is the wing length of females that emerged on day x

Mortality from first instars to emergence Results and Discussion Mortality from first instars to emergence Ae. aegypti Ae. albopictus Significantly different between poor and rich nutrition

Effect of temperature, diet and mixed species on the mortality Factors Effects (ANOVA Results) Ae. aegypti Ae. albopictus Temperature Yes Nutrition No Mixed species Temperature x Nutrition Temperature x Mixed species Significant=Yes, Non Significant=No

Development time from 1st instars to emergence in mixed species Female Male

Wing length of adult Ae. aegypti and Ae Wing length of adult Ae. aegypti and Ae. albopictus at 20, 25, 30 and 35 °C temperature Ae. aegypti ♀ Ae. albopictus ♀

Effects (MANOVA Results) Effects of temperature and diet on the development time and wing size in mixed species Factors Effects (MANOVA Results) Ae. aegypti Ae. albopictus Female Male Temperature Yes Nutrition Temperature x Nutrition No Significant=Yes, Non Significant=No

Sex ratio of Ae. aegypti and Ae. albopictus

In case of Ae. albopictus, more female in mixed and poor diet may compensate for the declining intrinsic rate of increase under these unfavorable conditions.

Per Capita Performance index (I) with 1:1 sex ratio

Estimated per capita performance index I in mixed species with absolute sex ratio Ae. albopictus was favored at 20°C - 25°C Ae. aegypti was favored at 25°C- 30°C. At 35°C, the population growth of both species was declined.

Comparative I in A. Poor Diet B. Rich Diet

Comaprative I in different diet conditions

Concluding remarks Population growth of Ae. albopictus was more stable, regardless of diet and temperature. Population growth of Ae. aegypti varied more with these two factors. These species-specific attributes may help explain the latitudinal distribution of the mosquitoes and degree of species dominance where they are sympatric.