No abstract

No abstract

We used microsatellites to assess genetic diversity and spatial structuring of the invasive apomictic New Zealand mudsnail (Potamopyrgus antipodarum) in the initial focal area of its recent North American invasion, a portion of the upper Snake River basin (Idaho) that is segmented by a series of hydropower dams. Thirty-four samples (812 total snails) from a 368 km reach of this drainage were genotyped for six loci. Sixty-five distinct clones were detected and grouped into four divergent clusters based on chord distances. Genetic structuring of populations was generally low. Our results indicate that the founding population(s) of this invasion was composed of a small number of putative clonal lineages which spread rapidly within this fragmented watershed owing to the enhanced dispersal ability of these parthenogens. The substantial genetic variation documented in this study suggests that caution should be used in the application of biological control measures for this pest species.

The human Achilles tendon (AT) consists of sub-tendons arising from the gastrocnemius and soleus muscles that exhibit non-uniform tissue displacements thought to facilitate some independent actuation. However, the mechanisms governing non-uniform displacement patterns within the AT, and their relevance to triceps surae muscle contractile dynamics, have remained elusive. We used a dual-probe ultrasound imaging approach to investigate triceps surae muscle dynamics (i.e., medial gastrocnemius-GAS, soleus-SOL) as a determinant of non-uniform tendon tissue displacements in the human AT. We hypothesized that superficial versus deep differences in AT tissue displacements would be accompanied by and correlate with anatomically consistent differences in GAS versus SOL muscle shortening. Nine subjects performed ramped maximum voluntary isometric contractions at each of five ankle joint angles spanning 10° dorsiflexion to 30° plantarflexion. For all conditions, SOL shortened by an average of 78% more than GAS during moment generation. This was accompanied by, on average, 51% more displacement in the deep versus superficial region of the AT. The magnitude of GAS and SOL muscle shortening positively correlated with displacement in their associated sub-tendons within the AT. Moreover, and as hypothesized, superficial versus deep differences in sub-tendon tissue displacements positively correlated with anatomically consistent differences in GAS versus SOL muscle shortening. We present the first in vivo evidence that triceps surae muscle dynamics may precipitate non-uniform displacement patterns in the architecturally complex AT.

The effects of nonpoint source pollution on salmonid incubation and embryo survival to emergence were evaluated on Rock Creek in south-central Idaho. New monitoring protocols were applied to evaluate effects of sediments and associated pollutants on spawning and recruitment of brown trout Salmo trutta. According to these new protocols, incubation success in artificial egg pockets is measured in terms of inlragravel dissolved oxygen (IGDO), percent fine sediment (<2.0 mm) in the substrate, and survival of embryos and alevins to emergence. Mean IGDO concentrations and saturation levels were significantly less (P < 0.05) at stations affected by agricultural pollutants than at a control station. Up to 40% of IGDO measurements were below 6.0 mg/L, the proposed water quality criterion for salmonid spawning in Idaho streams. Mean values for percent fine sediment were also higher at all impacted stations. Survival to emergence at the control station ranged from 18 to 83% and averaged 48%. Survival at impacted stations ranged from 0 to 54% and averaged 17%. Survival generally increased with mean IGDO concentrations above 8.0 mg/L and 70% saturation. A growth index expressed as the ratio of alevin total length to thermal units of exposure (summed daily degrees above 0°C) during stream incubation showed reduced alevin growth during incubation at impacted stations. Significant positive relationships were found between IGDO saturation and survival to emergence (P < 0.01). We found significant inverse relationships for percent fine sediment and survival (P < 0.05).

No abstract

No abstract

No abstract