Aquatic and terrestrial invertebrate drift in southern Appalachian Mountain streams: implications for trout food resources

1. We characterised aquatic and terrestrial invertebrate drift in six south‐western North Carolina streams and their implications for trout production. Streams of this region typically have low standing stock and production of trout because of low benthic productivity. However, little is known about the contribution of terrestrial invertebrates entering drift, the factors that affect these inputs (including season, diel period and riparian cover type), or the energetic contribution of drift to trout. 2. Eight sites were sampled in streams with four riparian cover types. Drift samples were collected at sunrise, midday and sunset; and in spring, early summer, late summer and autumn. The importance of drift for trout production was assessed using literature estimates of annual benthic production in the southern Appalachians, ecotrophic coefficients and food conversion efficiencies. 3. Abundance and biomass of terrestrial invertebrate inputs and drifting aquatic larvae were typically highest in spring and early summer. Aquatic larval abundances were greater than terrestrial invertebrates during these seasons and terrestrial invertebrate biomass was greater than aquatic larval biomass in the autumn. Drift rates of aquatic larval abundance and biomass were greatest at sunset. Inputs of terrestrial invertebrate biomass were greater than aquatic larvae at midday. Terrestrial invertebrate abundances were highest in streams with open canopies and streams adjacent to pasture with limited forest canopy. 4. We estimate the combination of benthic invertebrate production and terrestrial invertebrate inputs can support 3.3–18.2 g (wet weight) m⁻² year⁻¹ of trout, which is generally lower than values considered productive [10.0–30.0 g (wet weight) m⁻² year⁻¹]. 5. Our results indicate terrestrial invertebrates can be an important energy source for trout in these streams, but trout production is still low. Any management activities that attempt to increase trout production should assess trout food resources and ensure their availability.     

Experimental evidence quantifying the role of benthic invertebrates in organic matter dynamics of headwater streams

SUMMARY. 1. The insecticide methoxychlor was applied seasonally to one of three small headwater streams in the southern Appalachian Mountains in North Carolina, U.S.A. The initial application caused massive invertebrate drift (>1,000,000 organisms/week) and resulted in a community with few shredders and reduced abundances of most insect taxa.
2. Bacterial densities and microbial respiration rates were not affected by treatment.
3. Disruption of the invertebrate community resulted in significant reductions in leaf litter processing rates (50–74% reduction depending on leaf species) and in the amount of leaf litter processed annually (reduction of 25–28%).
4. Reductions in leaf litter processing rates resulted in significant reductions in fine particulate organic matter (FPOM) export. Declines in both concentration and total export were detectable within 1 week of treatment. Annual FPOM export was reduced to 33% of pretreatment levels. Alteration to the invertebrate community had a much greater effect on FPOM export than a severe (50–200 year) drought.
6. Course particulate organic matter (CPOM) export was not significantly influenced by treatment but was influenced by hydrologic differences among years.     

Acanthamoeba healyi N. Sp. and the Isoenzyme and Immunoblot Profiles of Acanthamoeba spp., Groups 1 and 3

ABSTRACT Two strains of Acanthamoeba isolated from human brain tissue and a strain of Acanthamoeba isolated from a fish were compared with 10 species of Acanthamoeba belonging to groups 1, 2 and 3 based on their isoenzyme profiles and antigenic characteristics. A total of 12 enzymes were studied. The isoenzymes and antigens were electrophoretically separated on polyacrylamide gradient gels, and the patterns obtained were compared after appropriate staining for particular enzymes and reactivities with homologous and heterologous rabbit anti- Acanthamoeba antisera. One of the human strains (CDC:1283:V013) was identified as A. healyi n. sp. because of its unique isoenzyme profiles for 11 of the 12 enzymes tested. The other human isolate was reidentified as A. culbertsoni because its isoenzyme profiles for 10 of 12 enzymes resembled those of A. culbertsoni , Lilly A-1 strain. Since the isoenzyme profiles and the antigenic patterns of the fish isolate as well were remarkably similar to those of A. royreba , it was considered as a strain of A. royreba . Polyacrylamide gradient gel electrophoresis appears to be a powerful technique for the study of isoenzymes and antigens of Acanthamoeba .     

Paradigmatic Processes in Culture Change

Paradigmatic processes in culture change are defined, in the sense of Thomas Kuhn, as the consequence of long-continued deliberate effort by numbers of persons to innovate within a recognized technical, artistic, or intellectual tradition (or "school" or "discipline"). The evolving paradigm will often, after a certain point of development, attract exploitation; there will then occur various functionally entailed social-cultural consequences; and ultimately efforts will be made to rationalize the change in religious, ethical, and philosophical terms.     

Analyses of genetic change-over in Drosophila populations

Genetic change-overs in Drosophila populations similar to those frequently observed in microbial ones maintained in chemostats are described. In two cases, the change-overs were revealed by an abrupt and sustained increase in the probability that two independently sampled lethal chromosomes proved to be allelic. These favored lethals (or closely linked non-lethal elements) were estimated to have fitnesses 1.30–1.35 in combination with “ordinary” lethals or 1.05–1.10 in combination with non-lethal chromosomes (fitness 1.00 is assigned to carriers of non-lethal chromosomes only). A decrease in the frequency of lethal chromosomes in a third population was adequately explained by postulating the origin of a non-lethal “favored” element whose relative fitness was 1.25, a value similar to those estimated above. Genetic change-over in populations is discussed in relation to biochemical and morphological conservatism.     

Alternative Mating Tactics and Evolutionarily Stable Strategies

Difficulties with applying Evolutionarily. Stable Strategy (ESS)methodology and terminology to alternative mating behaviors(in which some males in local populations adopt strikingly different,often non-competitive, behavioral patterns) are reviewed. Definitionsfor "tactic" (behavioral phenotype) and "strategy" (evolvedset of rules for expressing tactics) are given. Inconsistentand incorrect applications of "mixed," "pure," and "conditional"ESSs are discussed. Cases of condition-dependent alternative mating tactics arereviewed. Because most alternative behaviors are condition dependent,neither their population-wide nor individual fitness contributionsare expected to equal the fitness contributions of "primary"tactics. Individuals should, however, switch tactics at "equalfitness points." A particular conditional tactic will persistwhen its maintenance cost (genetic or physiological) is lessthan its fitness contribution. In only exceptional cases arethe fitness contributions of tactics expected to be equal: 1)genetic polymorphisms, 2) stochastic "mixed" ESSs, 3) frequency-dependentchoice and, 4) arbitrary assessment. Although alternative tacticsmay occur in cases of genetic polymorphism or genetic equipotence,most mating tactics probably occur when continuous heritablevariation in underlying conditional strategy exists. Selectionfor genetically influenced "roles" (genetic background) mayalso uncover apparent heritability.     

Movement of Assimilated Nitrogen from the Root System of the Field Pea (Pisum arvense L.)

Changes in the composition of the amino fraction of bleedingsap collected from decapitated root systems of field pea werestudied during the period of transition from cotyledon nutritionto the commencement of nitrogen fixation by root nodules. Outputand composition of bleeding sap are described for uninoculatedseedlings following application to the rooting medium of nitrate,ammonium, or urea. Assimilation by the root system of any externalsource of nitrogen results in progressive increase in the outputof all bleeding-sap components, particularly the amide asparagine.The relative proportions of the various amino compounds andthe balance of organic and inorganic nitrogen in the bleedingsap were found to vary with the source of nitrogen made availableto the root system.