Effects of an Invasive Parasite on a Coevolved Host-Parasite System: Ascogregarina Barretti and Aedes Triseriatus

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Biological Sciences


Steven Juliano

Mentor Department

Biological Sciences


The antagonistic host-parasite relationship can drive population level effects, potentially influenced by a variety of environmental factors. The presence of invasive parasites within the habitat can alter established host-parasite relationships, affecting host fitness and infection prevalence, parasite burden, and infection success of the native parasite within the host. The mosquito, Aedes triseriatus, is native host to protozoan parasite, Ascogregarina barretti. This parasite exists within the host habitat and is ingested by the host while foraging; after ingestion, the parasite consumes host resources in the larval midgut before reproducing within the Malpighian tubules during the host pupal stage. A. triseriatus also experiences infection by the invasive parasite, Ascogregarina taiwanensis. Similar to A. barretti, A. taiwanensis is ingested by the host during foraging and consumes host resources within the larval midgut. However, A. taiwanensis has not been known to successfully reproduce within A. triseriatus, making these infections unproductive for the parasite but still potentially costly for the host. We tested the hypotheses that: 1) The presence of an invasive parasite will negatively impact native parasite fitness (decreased infectious burden, decreased infection success) through immune induction of the host, and 2) Coinfection with the native and invasive parasite will negatively impact host fitness (increased larval development time, decreased reproductive fitness) through increased costs of infection. First instar A. triseriatus larvae were exposed to habitats with one of three parasite treatments: no parasite, A. barretti, or A. barretti and A. taiwanensis. Randomly selected 4th instar larvae were dissected to determine parasite burden. Adults were dissected to determine parasite prevalence, burden, and parasite reproduction success. All treatments were assessed for survivorship to adulthood and estimated per capita population growth rate of the host.



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