Factors contributing to the host specificity of the frog-feeding mosquito Culex territans Walker (Diptera: Culicidae)
Creators: name: Bartlett, Kristen
Publisher: name: No Publisher Supplied
Year: 2009

description: Culex territans Walker acquires bloodmeals from amphibian hosts. Females overwinter as inseminated adults and exit diapause in New Jersey when spring peepers (Pseudacris crucifer) are calling. We tested the hypothesis that C. territans uses amphibian vocalizations as a long distance attractant.  Two thirds of females oriented toward sound across all experiments. Females allowed to orient towards or away from a frog call, bird song, live frog, or control (a plugged in compact disc player) exhibited positive phonotaxis only to the frog call. Females exhibited positive phonotaxis to calls of P. crucifer, Hyla versicolor (northern gray tree frog), Bufo americanus (American toad), and R. clamitans (green frog), but were not attracted to calls of R. catesbeiana (bullfrog), R. sylvatica (wood frog), or control. Multiple regression analysis showed that call frequency is the best predictor for phonotaxis, with pulse duration and call amplitude increasing the attractiveness of the source. When exposed to P. crucifer calls at increasing sound intensity levels, females oriented to calls in the range of 50 to 75 dB, with particle velocities of 0.02 to 0.3 mm/s, indicating that phonotaxis occurs at distances greater than 5 m from the source.To examine synchrony of Cx. territans with amphibian species, ten larval habitat sites were sampled weekly from March to November of 2004.  Culex territans larvae were temporally and spatially associated with the green frog, Rana clamitans Latrielle.  We predicted that if the preferred hosts were abundant at low temperatures, then Cx. territans might be able to digest bloodmeals at those same temperatures. Using the thermal heat summation model, 192.3 days above 3.9°C were required to complete the gonotrophic cycle. This is the lowest thermal minimum reported for a Nearctic species of mosquito.  Using this model, we calculated that the first larvae of Cx. territans field- collected on 6 May 2004 were the progeny of females which bloodfed during the last week of March or first week of April.  We conclude that Cx. territans has physiological mechanisms that allow them to take advantage of early season bloodmeal sources.The bloodmeals of field-collected female Culex territans (Diptera: Culicidae) were concurrently assayed for the presence of trypanosomes and for vertebrate host identification. We amplified vertebrate DNA in 42 of 119 females, and made positive identification to the host species level in 29 of those samples.  Of the 119 field-collected Cx. territans females, 24 were infected with trypanosomes.  Phylogenetic analysis placed the trypanosomes in the amphibian portion of the aquatic clade of the Trypanosomatidae.  These trypanosomes were isolated from Cx. territans females that had fed on the frog species, Rana clamitans, R. catesbeiana, R. virgatipes, and R. spp.  Results support an unknown lineage of dipteran transmitted amphibian trypanosomes occur within the aquatic clade. The frequency in which female Culex territans acquire trypanosomes, through diverse feeding habits, indicates a new relationship between amphibian trypanosomes and mosquitoes that has not been previously examined.  Combining Trypanosoma species, invertebrate, and vertebrate hosts to existing phylogenies can elucidate trypanosome and host relationships.