Arctic tundra wetlands support abundant waterbirds, but invertebrate prey communities may change with climate warming. Increased influx of nutrients and labile dissolved organic matter (DOM) from thawing permafrost may alter the relative importance of organic matter (OM) sources, with associated changes in relative biomass of taxa dependent on different sources. In six wetland types, we used stable isotopes (δ13C, δ15N) to compare contributions of four OM sources (periphytic microalgae, cyanobacteria, macrophytes, and peat) to the diets of nine macroinvertebrate taxa. Relative OM contributions within invertebrate taxa were similar among wetland types. Cyanobacteria comprised only 2–7% of OM sources for all taxa in shallow wetland types (<1 m), but up to 25% for oligochaetes and Physidae in deeper wetlands. Macrophytes were minor OM sources (<13%) in all wetland types except deep open lakes (21–26%). Peat typically comprised 20–40% of OM sources except for Physidae (mostly 50–80%). Microalgae were the dominant OM source for most taxa (47–78%, mean ⁓60%), although less for Oligochaeta and much less for Physidae (9–32%). High periphyton production with very depleted δ13C values likely results from continuous daylight illuminating shallow depths, high N and P levels, and very high pCO2 derived from bacterial respiration of DOM leached from thawing permafrost. Invertebrate consumption of microalgae and peat appears often to involve bacterial intermediates. Impacts of warming on invertebrate prey availability will likely depend not on shifts in OM sources, but on changes in overall area or number of shallow ponds.

Nemerteans are common invertebrates along coastlines in both temperate and arctic climates throughout the world. Amphiphorus imparispinosus is a carnivorous member of this phylum that is found abundantly in the intertidal areas of the Oregon coast. As in many other invertebrate phyla, endocrine integration within the nemerteans is thought to be accomplished by neurosecretory mechanisms. In Amphiphorus the presence of these neurosecretory systems has not been previously shown. This project was undertaken to determine if neurosecretory cells are present within the central nervous system of this species and. further, to examine seasonal changes in the number and appearance of these cells. The second objective of this research was to determine the reproductive cycle of Amphiphorus and to examine a possible correlation between this cycle and seasonal changes in the neurosecretory system.

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Whether active or passive, dispersal accompanied by gene flow shapes the population genetics and evolutionary divergence of species. Indirect methods which use genetic markers have the ability to assess effective dispersal—that which resulted in gene flow. My objective was to see if an aquatic insect and an obligate aquatic invertebrate show similar phylogeographic patterns and genetic uniqueness. Hyalella azteca and Callibaetis americanus were collected from 4-5 springs in each of six basins in the Great Basin of western North America. No dispersal or genetic studies of C. americanus have been conducted to date. However, several studies focusing on mtDNA diversity of H. azteca have revealed a tremendous degree of cryptic diversity in the desert springs of the Great Basin. Nested clade phylogeographical analysis (NCPA), FST values, AMOVA, and Mantel tests were used to examine geographical associations. I also used traditional phylogenetic approaches including maximum parsimony (MP) and likelihood (ML) analyses using cytochrome c oxidase subunit I (COI), 28S, and 16S as genetic markers. The mitochondrial COI sequence divergences in C. americanus were higher than H. azteca COI divergences within springs but lower among springs. FST values were very high in H. azteca reaching near fixation for certain alleles. C. americanus FST values were lower suggesting greater gene flow and, consequently, greater dispersal rates. Even though Mantel tests did not detect significant isolation by distance when evaluating all haplotypes together, nested clade analysis was able to examine smaller networks of related haplotypes and detect significant isolation by distance. Whereas the genetic structure in C. americanus was dominated by restricted gene flow with isolation by distance, H. azteca was characterized more by gradual range expansion followed by fragmentation. Mayflies likely showed more gene flow than amphipods because of their flight capabilities, but movement was still restricted by long distances between isolated springs.

The sensation of mechanical signals is vital for all animals. For this task Drosophila larvae are equipped with chordotonal organs. These are specialized mechanosensory organs which are composed of multicellular subunits. In this study I show how metabotropic signaling by the adhesion GCPR CIRL interacts with part of the ionotropic pathways during mechanosensation in sensory neurons of the pentascolopidial chordotonal organ (lch5). CIRL modulates cAMP levels in sensory neurons and thereby shapes the receptor potential response to mechanical stimuli. Here, CIRL forms a functional interaction with the TRP channel NOMPC in which nompC is epistatic to Cirl. Furthermore, the evidence presented suggest the presence of another target of CIRL and the involvement of a further signaling pathway besides cAMP modulation. In the second part of the study, I describe a method to express the anion-selective channelrhodopsin GtACR1 in individual of the five neurons of the lch5. For this I used the MARCM approach which generates genetic mosaics during the development of the neurons of interest. Thereby a specific subset of cells deriving from a common precursor expresses the desired protein GtACR1.

Benthic macroinvertebrate communities of Huntington River, Emery County, Utah were studied to determine effects of sedimentation from construction of Electric Lake Dam, a state highway, and two bridges. Approximately 900 benthic samples were collected from riffle areas above, in, and below the construction zone from January, 1971 to December, 1973. Two settling basins below construction sites were effective in limiting scouring of downstream communities. Heavy silt deposition was limited to a 1-km stream reach. Number of indicators, density, and biomass were reduced in the construction zone during periods of sediment input. During periods of scouring, density and biomass were reduced; however, community diversity (d̅) increased due to a reduction of the more populous taxa. The mean d̅ value in the construction zone was 2.05 compared to 2.81 outside. Ordination analysis revealed dissimilarity in communities in, above, and below the construction zone. Specific indicators showed varying response to sedimentation. Recovery was rapid following scouring but slow following sedimentation.

Macroinvertebrate populations in the Weber River, Summit County, Utah, were analyzed to determine what effects channelization resulting from Interstate-80 construction and water impoundment had on the standing crop, species diversity and species composition. Bottom samples were collected monthly from riffle areas in channeled and unchanneled sections and above Echo and Wanship Reservoirs. Macroinvertebrate populations in the channeled areas were similar in standing crop, species diversity and species composition to those in unchanged areas within six months following channelization. Species diversities were higher (d=4.1, 3.7) above the reservoirs than below (d=2.0). The reservoirs restricted the distribution of several species of macroinvertebrates. The effects of channelization on the macroinvertebrate fauna in the Weber River were negligible, but water impoundment influenced the species composition and species diversities of the populations occurring in the tailwater.

No description available.

Exotic invasive plant species can alter aquatic habitats potentially influencing the macroinvertebrate community and foraging fishes. Therefore, I investigated the hypothesis that Hydrilla verticillata will alter habitat important to macroinvertebrate community structure and bluegill foraging efficiency. Studies were conducted in ponds and aquaria. At the pond level, macroinvertebrate abundance, richness, and biomass in a hydrilla-dominated habitat did not differ significantly from a diverse plant habitat. Indicator taxa did differ significantly between respective treatments. The data suggest hydrilla beds may not provide increased macroinvertebrate abundance and richness compared to diverse plant beds as previously thought. In aquaria, habitat complexity (Ihv) and light transmittance were influenced by increasing the homogeneity of hydrilla in an aquatic bed habitat. In addition, bluegill foraging efficiency was affected negatively by increasing spatial complexity of a hydrilla dominated habitat. Therefore, a shift to a monotypic hydrilla habitat can alter macroinvertebrate community composition and impact bluegill foraging success.