Monday, May 23, 2016
10:30 - 12:00

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10:30 - 10:45: / 314 HEAVY METAL POLLUTION AND PARASITISM AFFECT MAYFLY DRIFT BEHAVIOR AND SUSCEPTIBILITY TO STONEFLY PREDATION

5/23/2016  |   10:30 - 10:45   |  314

HEAVY METAL POLLUTION AND PARASITISM AFFECT MAYFLY DRIFT BEHAVIOR AND SUSCEPTIBILITY TO STONEFLY PREDATION Heavy metals discharged into streams from abandoned and active mines in the western USA can affect the behavior and interactions of grazing insects with their predators. Previous research in unpolluted streams showed that mayfly dispersal behavior is altered by endoparasitic mermithid nematodes. Our study examined the independent and interactive effects of metal pollution and parasites on mayfly dispersal and susceptibility to predation. Using streamside microcosms, we compared the drift and predation rates by stoneflies (Megarcys signata) of parasitized and unparasitized mayflies (Baetis bicaudatus) originating from metal-polluted and unpolluted reference streams. Results showed that daytime drift of parasitized individuals was higher than unparasitized individuals in both stream types. However, significant interactions between metal exposure and parasitism indicated that nighttime and total drift of unparasitized mayflies exceeded those of parasitized mayflies in metal-polluted streams. Therefore, dispersal depended on both exposure to heavy metals and parasitism. Exposure to metals, but not parasitism, increased susceptibility of mayflies to predation by nocturnal stoneflies. These findings demonstrate the importance of evaluating environmental context involving abiotic stressors on interactions between mayflies and their enemies

Jasmine Hamilton (Primary Presenter/Author), California State University, Sacramento, hamiltonjasmine27@yahoo.com;


Barbara Peckarsky ( Co-Presenter/Co-Author), University of Wisconsin, Madison, peckarsky@wisc.edu;


Kara Cromwell ( Co-Presenter/Co-Author), University of Wisconsin-Madison, kara.cromwell@gmail.com;


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10:45 - 11:00: / 314 HOW DO HOST-PARASITE LIFE HISTORY AND ABIOTIC ENVIRONMENTAL CONTEXT INTERACT TO DETERMINE PARASITE PREVALENCE?

5/23/2016  |   10:45 - 11:00   |  314

HOW DO HOST-PARASITE LIFE HISTORY AND ABIOTIC ENVIRONMENTAL CONTEXT INTERACT TO DETERMINE PARASITE PREVALENCE? Parasite infection risk can be affected both by attributes of organisms and their environmental context. Following observations that mermithid (Nematoda) parasite prevalence in Baetis mayflies increased with the quantity of oviposition habitat available to the host, we hypothesized that oviposition habitat attracted dispersal of both healthy and parasitized hosts, leading to aggregations and higher infection rates in sites that would otherwise favor host recruitment. To test this hypothesis, we used a 2-year field experiment in which instream oviposition habitat was increased or decreased relative to controls (N=4). We measured no change in parasite prevalence after the manipulation, suggesting that life history traits other than selective oviposition and/or site traits other than oviposition habitat influence the distribution of parasitism. Continuing the search for unknown drivers, we have observed that warmer streams have not only lower parasite prevalence, but also hosts that are more developmentally advanced at the date when parasitic infections begin, implying that phenological mismatch could decrease parasitism in warmer streams. Because the effect of temperature cannot be disentangled from coexisting environmental variables in situ we propose an experimental test.

Kara Cromwell (Primary Presenter/Author), University of Wisconsin-Madison, kara.cromwell@gmail.com;


Barbara Peckarsky ( Co-Presenter/Co-Author), University of Wisconsin, Madison, peckarsky@wisc.edu;


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11:00 - 11:15: / 314 THE EFFECT OF PARASITISM ON DRIFT BEHAVIOR AND CONSEQUENCES FOR TROUT PREDATION ON LARVAE OF THE MAYFLY BAETIS BICAUDATUS

5/23/2016  |   11:00 - 11:15   |  314

THE EFFECT OF PARASITISM ON DRIFT BEHAVIOR AND CONSEQUENCES FOR TROUT PREDATION ON LARVAE OF THE MAYFLY BAETIS BICAUDATUS For parasites that utilize only one host for their development, survival of the parasite depends on survival of their host. This is the case with the mayfly Baetis bicaudatus, whose larvae are parasitized by the mermithid nematode Gasteromermis sp. in streams in western Colorado, USA. Previous studies conducted in artificial environments report conflicting results regarding the effect of parasitism on Baetis drift behavior, which not only facilitates foraging for benthic algae, but also increases their vulnerability to drift-feeding salmonid predators.To resolve previous conflicts, in 12 natural streams we collected drifting macroinvertebrates, and compared the prevalence of parasitized Baetis to their benthic prevalence. We also used gastric lavage to examine the stomach contents of brook trout (Salvelinus fontinalis), and compared parasite prevalence in trout diets to that of the benthos. Results showed that parasitized Baetis drifted less frequently than healthy individuals. In addition, we observed a significantly lower percentage of parasitized Baetis in trout diets as compared to the surrounding habitat. These results support the hypothesis that the parasite manipulates the host to favor safety from predators over food consumption.

Benjamin Swift (Primary Presenter/Author), Rocky Mountain Biological Laboratory, benjibear3@gmail.com;


Kara Cromwell ( Co-Presenter/Co-Author), University of Wisconsin-Madison, kara.cromwell@gmail.com;


Barbara Peckarsky ( Co-Presenter/Co-Author), University of Wisconsin, Madison, peckarsky@wisc.edu;


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11:15 - 11:30: / 314 BIOTIC INTERACTION ENHANCES SURVIVAL AND FITNESS: INTERSPECIFIC FACILITATION AMONG AQUATIC MACROINVERTEBRATES

5/23/2016  |   11:15 - 11:30   |  314

BIOTIC INTERACTION ENHANCES SURVIVAL AND FITNESS: INTERSPECIFIC FACILITATION AMONG AQUATIC MACROINVERTEBRATES A mesocosm experiment was performed to determine the effect of biotic interaction on survival and fitness of aquatic macroinvertebrates. Two species of Trichoptera (Micropterna sequax and Potamophylax rotundipennis) were used in homogeneous and heterogeneous populations. Emergence success of 900 individuals was scored and fitness was measured in terms of wing span and biomass. We found that a biotic interaction between the two species resulted in a higher emergence success of M.sequax, while P.rotundipennis was not significantly affected by this interaction, indicating a interspecific facilitation. Additionally, M.sequax developed larger wings and had a higher biomass in heterogeneous populations, suggesting even more clearly the benefits of a biotic interaction with P.rotundipennis. Our key findings show a clear positive effect of species diversity on the survival and fitness of M.sequax and only few negative effects on P.rotundipennis males. Even though both species are similar in terms of niche preference and life-history strategy, this result shows an interspecific facilitation that affects survival and fitness. These effects can influence ecosystem functioning in the long-term and emphasize the importance of species diversity within freshwater streams.

Judith Westveer (Primary Presenter/Author), University of Amsterdam, j.j.westveer@uva.nl;


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11:45 - 12:00: / 314 BURROWING BEHAVIOR OF UNIONID MUSSELS IN CENTRAL TEXAS

5/23/2016  |   11:45 - 12:00   |  314

BURROWING BEHAVIOR OF UNIONID MUSSELS IN CENTRAL TEXAS Freshwater mussels are one of the most imperiled groups of organisms globally. In Texas, 15 of approximately 50 species are considered threatened. A better understanding of burrowing behavior and its drivers is needed to design effective survey protocols, facilitating the collection of distribution data, a crucial step for developing conservation strategies. Our objective was to examine burrowing behavior and potential drivers at three different field sites and with lab experiments. Preliminary results show that a higher percentage of mussels in the San Marcos River were burrowed in winter (Jan 2015, 85%) than late fall (Oct 2014, 50%), and mussels were burrowed more at a sandy site in the San Antonio (89±1.1%, mean ± SE of visible shell, n=119) compared to a gravel dominated site in the Guadalupe River (40±3.4%, n=100). Lab experiments indicated that despite temperature changes mussels moved approximately as much down as up, but 57% of mussels stopped moving when temperatures decreased from 24°C to 14°C-15°C. Our results suggest that surveys may need to follow different guidelines depending on local conditions such as substrate and temperature.

Bianca Hernandez (Primary Presenter/Author), Texas State University, bah118@txstate.edu;


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