ZOOS AS EXPERIMENT ENVIRONMENTS: BIOLOGY OF LARVAL AND ADULT MOSQUITOES (DIPTERA: CULICIDAE)

Zoos are a unique environment where humans and animals are in close daily contact, potential mosquito habitats exist, exotic plants and animals are introduced regularly, and wild animals roam. Studies of mosquito behaviors in zoos will lead to a better understanding, both within and outside zoos, of disease transmission routes and mosquito biology. To investigate whether the unique assemblage of habitats in zoos affects mosquito behavior, I sampled larvae and adults in the Greenville Zoo and the Riverbanks Zoo, South Carolina, USA, from March 2008 to January 2011. The objectives of my study were to investigate mosquito oviposition behavior, blood-host usage, and transmission of the causative agent of dog heartworm (Dirofilaria immitis); document the structure of the mosquito pyloric armature; and provide zoos with suggestions for mosquito control. My results underscore the medical and veterinary importance of studying mosquito blood feeding ecology in zoos, and the experimental utility of zoos for studying mosquito behavior. A total of 1,630 larvae and 4,349 adults representing 16 species was collected and identified. The most common species were Aedes albopictus, Ae. triseriatus, Culex erraticus, Cx. restuans, and Cx. pipiens complex. Principal components and multiple logistic regression analyses showed that across both zoos the overall larval mosquito presence (regardless of species) was predicted by ambient and site temperature, precipitation, dissolved oxygen, presence of natural habitats, and absence of aquatic vegetation. Pairwise species associations indicated significant habitat-based relationships between larvae of Ae. albopictus and Ae. triseriatus, and Cx. pipiens complex and Cx. restuans. Recommendations to zoo personnel, regarding larval mosquito habitat management, were to reduce or eliminate artificial containers and shade sources greater than or equal to 2 m above standing water, use mosquito larvicides when source reduction is not possible, and receive training in recognizing and mitigating larval mosquito habitats. Mosquitoes fed on captive animals, humans, and wild animals, and took mixed bloodmeals. Blood hosts included 1 amphibian species, 16 bird species, 10 mammal species (including humans), and 2 reptile species. Minimum flight distances (dispersal) from host locations ranged from 15.5 m to 327.0 m, with a mean of 94.1 m ± 13.4 m. No mosquitoes tested (n = 45) were positive for D. immitis. The pyloric spines of Ae. albopictus, Ae. j. japonicus, Ae. triseriatus, An. punctipennis, Cx. pipiens complex, Cx. restuans, Or. signifera, and Tx. rutilus were photographed and measured. Differences exist in qualitative and quantitative spine structure, with Aedes spp. forming one general group, Culex spp. another, and An. punctipennis and Or. signifera a third. The one specimen of Toxorhynchites rutilus examined was most like Culex spp. mosquitoes. Larval mosquito-habitat, adult mosquito-host associations, and pyloric armature and spine structures generally conformed to previously published accounts, indicating that mosquito biology inside zoos represents mosquito biology outside zoos. Therefore, zoos can be used for experiments not feasible in the field. However, novel variation (e.g., new, exotic host records) recorded in mosquito species warrants further investigation in zoos. My study demonstrates that zoos can be used as experiment environments to study mosquito behaviors (e.g., oviposition cues, innate versus learned host preferences, mosquito dispersal, and home range memory), and that findings can be extrapolated to non-zoo areas, while also providing medical and veterinary benefits to zoo animals, visitors, and the public