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Larval violence in neotropical jungle mosquitoes: investigations of interspecific predation mechanics in two Sabethene mosquitoes
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Boyd, Taylor
McFadden, Shannon
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Denver, CO
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Metropolitan State University of Denver
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conference poster

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Presented at the 2020 MSU Denver Undergraduate Research Conference
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Faculty mentor: Robert Hancock
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Department of Biology

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Auraria Institutional Repository
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Auraria Library
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RESEARCH POSTER PRESENTATION DESIGN © 2012 www.PosterPresentations.com RESEARCH POSTER PRESENTATION DESIGN © 2019 www.PosterPresentations.com Intraguild predation by mosquito ( Diptera : Culicidae) larvae is widespread across the taxa, confirmed in at least thirteen genera 1 9 . The manifestation of this behavior is however vastly diverse in the following aspects: dependency on predation (facultative or obligate), prey catching mechanisms along with associated morphology, and prey selection (intraspecific or interspecific). In this study the occurrence of interspecific predation and cannibalism (intraspecific predation) is investigated in order to fully describe unique voracious behavior within the Neotropic species Sabethes cyaneus and yellow fever vector Sa. chloropterus 10 . INTRODUCTION The Sabethes spp. larvae used in the study were from colonies originally established by R. G. Hancock and W. A. Foster from mated females collected from Isla Majé , Lago Bayano Panamá in 1988. These colonies as well as Aedes aegypti and Ae . albopictus (prey) colonies have been housed and maintained at Metropolitan State University of Denver at 27 ± 1 ° C with a 12:12 light:dark cycle. Larvae for the experiments described below were reared in plastic trays filled with aged tap water and fed powdered Tetramin ® twice weekly. To assess the occurrence and frequency of interspecific and intraspecific predation, Sabethes larvae were isolated from recently fed trays and placed individually into a (3.3 cm 2 ) cell of a silicone ice tray filled with aged tap water. A potential prey larva (instars of the same species, a species within the same genus, or a different genus Aedes ) was then added to each occupied cell. Observations were recorded every 24hr for up to 72hr. To further document the possible occurrence of cannibalism and fully elucidate the prey catch mechanism by sabethine larvae, high speed microvideography was used. Recordings at 180 frames per second (fps) were made using Panasonic Lumix GH5 cameras fitted with macro lenses including an Infinity Optical Robusto system (Infinity Optical Company, Boulder, CO). Recordings of 500 1200fps were made using a Ximea (Münster, Germany) XiQ USB 3.0 Superspeed camera (model M0013cG ON) fitted with a Kern Switar 75mm c mount Macro lens. The range of the predatory strike was investigated in 15 minute overhead recordings of trials during which six 4 th instar Sa. cyaneus and Sa. chloropterus respectively were paired against a 1 st or 2 nd instar Ae. aegypti . Trials were conducted in silicone ice trays. Mean distance to prey was compared using one way anova and the Turkey Kramer test. MATERIALS & METHODS Sa. cyaneus and Sa. chloropterus were observed to have essentially identical predation mechanics. Initiation occurs predominately from one of two positions: surfaced (respiring) or lying on the bottom of the container. In both instances, the dorsa is normally facing the nearest surface as larvae appear to overwhelmingly prefer positions close to the walls of the container (Figure 1a). Once prey is detected the maxillae flare (Figure 1b) right before both the anterior and posterior part s o f the body are thrust towards the prey at a high speed. During this action the sclerotized siphon strikes the prey, bringing it directly to the mouth, between the maxillae, and once secure the predator clamps down (Figure 1c). This entire action occurs within approximately 16 milliseconds. The predator customarily thrashes the caught prey violently from side to side with quick motions of its head, sometimes even resecuring the position of the prey between the mandibles using its siphon. Prey consumption, which is typically incomplete in this species, involves the action of teeth on the mandibles, which cut into hel d prey (Figure 1d). CONCLUSIONS Both Sa. cyaneus and Sa. chloropterus were observed preying on Ae. aegypti and Ae. albopictus . Mean strike distance between species was significantly heterogeneous ( Turkey Kramer test, P>0.05). Cannibalism was readily observed within Sa. chloropterus even without starvation of the larvae. However, results are inconclusive on whether Sa. cyaneus cannibalize. We suspect the behavior in this species may be only prevalent in response to starvation as seen in other species such as Culex pipens 7 however further data is needed to confirm . Other preliminary results allude to the presence of interspecific predation by 4 th instar Sa. chloropterus on younger 2 nd /3 rd Sa. cyaneus and a lack of predation when the roles are reversed. Both Neotropic species utilize the unique siphon strike to capture their prey. REFERENCES 1.Pramanik, S., Banerjee, S., Banerjee, S., Saha , G. K. & Aditya, G. Observations on the predatory potential of Lutzia fuscana on Aedes aegypti larvae: Implications for biological control ( Diptera : Culicidae). Fragm . Entomol . 48 , 137 142 (2016). 2.Lounibos, L. P. BEHAVIORAL CONVERGENCES AMONG FRUIT HUSK MOSQUITOES. Florida Entomol . 66 , 32 41 (1983). 3.Ratsirarson, J. & Silander , J. A. Structure and Dynamics in Nepenthes madagascariensis Pitcher Plant Micro Communities. Biotropica 28 , 218 227 (1996). 4.Mogi, M. & Chan, K. L. Predatory habits of dipteran larvae inhabiting Nepenthes pitchers. Raffles Bull. Zool. 44 , 233 245 (1996). 5.Digma, J. R., Sumalde , A. C. & Salibay , C. C. Laboratory evaluation of predation of Toxorhynchites amboinensis ( Diptera:Culicidae ) on three mosquito vectors of arboviruses in the Philippines. Biol. Control 137 , 104009 (2019). 6.Koenraadt, C. J. M. & Takken , W. Cannibalism and predation among larvae of the Anopheles gambiae complex. Med. Vet. Entomol . 17 , 61 66 (2003). 7.El Husseiny , I., Elbrense , H., Roeder, T. & El Kholy , S. Hormonal modulation of cannibalistic behaviors in mosquito (Culex pipiens ) larvae. J. Insect Physiol. 109 , 144 148 (2018). 8.Dennehy, J., Robakiewicz , P. & Livdahl , T. Nordic Society Oikos Larval Rearing Conditions Affect Kin Mediated Cannibalism in a Treehole Mosquito.No Title. Oikos 95 , (2001). 9.Mastrantonio, V. Cannibalism in temporary waters: Simulations and laboratory experiments revealed the role of spatial shape in the mosquito Aedes albopictus. PLoS One 13 , 1 12 (2018). 10.DE RODANICHE, E. & GALINDO, P. Isolation of Yellow Fever Virus from Haemagogus Mesodentatus , H. Equinus and Sabethes Chloropterus Captured in Guatemala in 1956. Am. J. Trop. Med. Hyg . 6 , 232 237 (1957). 11.Ralph E. Harbach . Ontogeny of the Larval Stage of Sabethes Chloropterus With Special Reference to Setal Development and Phylogenetic Implications for the Family Culicidae ( Diptera ) . Mosquito Systematics vol. 23. ACKNOWLEDGEMENTS Metropolitan State University of Denver Taylor Boyd, Shannon MacFadden, and Robert Hancock PhD Larval violence in Neotropical jungle mosquitoes: investigations of interspecific predation mechanics in two sabethine mosquitoes Fig. 1. Depiction of predation mechanics of Sa. chloropterus on Ae. aegypti over one second. 1a. Larva filter feeding, maxillae tucked in. 1b. Pre strike position, maxillae flared. 1c. Post strike siphon capture. 1d. Prey consumption. RESULTS Fig. 2. Mean prey distance (dashed lines) and 95% confidence regions (dotted lines) for successful siphon strikes of Sa. chloropterus (left) and Sa . cyaneus (right) larvae. The means were significantly heterogeneous (one way anova , F 1,39 =8.882, P =0.0049; Turkey Kramer test, P>0.05) 1,000 milliseconds 16ms 1a. 1b. 1c. 1b. 1a. 1b. 1c. 1d. 1c. 1c. Sa. cyaneus adult by K. Custer 2020 Sa. chloropterus adult by R. G. Hancock 1991 Special thanks to Woodbridge A. Foster, PhD for providing the original Sa. cyaneus and Sa. chloropterus colonies used in this study. Thanks to Shawn Ward Stoffa for their role in rearing and maintenance of the colonies as well as Johnathan Dyhr, PhD for his assistance in high speed filming . Contact: tboyd12@msudenver.edu ; smacfadd@msudenver.edu Fig. 3. Developmental changes from the 1 st to 4 th instar of Sa. chloropterus larvae. I. 1 st instar with unsclerotized siphon and relatively underdeveloped mouthparts. II. 2 nd instar, during this stage siphon will completely sclerotize, development of sensory structures (setae, posterior filaments) on anterior. III. & IV. 3 rd and 4 th instars respectively, size increases dramatically, setae branch out 11 . Sa. chloropterus was observed predating as early as the second instar. This development in behavior coincides with the development of both the maxillae and the siphon (See Figure 3). In this instar the terminal hook like projection and lateral teeth of the maxillae take form. The siphon also advances within this stage and is now fully sclerotized, longer, and equipped with setae and a posterior row of filaments 11 .