Multiple watershed alterations influence fish community structure in Great Plains prairie streams

Stream fish distributions are commonly linked to environmental disturbances affecting terrestrial landscapes. In Great Plains prairie streams, the independent and interactive effects of watershed impoundments and land cover changes remain poorly understood despite their prevalence and assumed contribution to declining stream fish diversity. We used structural equation models and fish community samples from third‐order streams in the Kansas River and Arkansas River basins of Kansas, USA to test the simultaneous effects of geographic location, terrestrial landscape alteration, watershed impoundments and local habitat on species richness for stream‐associated and impoundment‐associated habitat guilds. Watershed impoundment density increased from west to east in both basins, while per cent altered terrestrial landscape (urbanisation + row‐crop agriculture) averaged ~50% in the west, declined throughout the Flint Hills ecoregion and increased (Kansas River basin ~80%) or decreased (Arkansas River basin ~30%) to the east. Geographic location had the strongest effect on richness for both guilds across basins, supporting known zoogeography patterns. In addition to location, impoundment species richness was positively correlated with local habitat in both basins; whereas stream‐species richness was negatively correlated with landscape alterations (Kansas River basin) or landscape alterations and watershed impoundments (Arkansas River basin). These findings suggest that convergences in the relative proportions of impoundment and stream species (i.e., community structure) in the eastern extent of both basins are related to positive effects of increased habitat opportunities for impoundment species and negative effects caused by landscape alterations (Kansas River basin) or landscape alterations plus watershed impoundments (Arkansas River basin) for stream species.     

Microhabitat use of the diamond darter

The only known extant population of the diamond darter (Crystallaria cincotta) exists in the lower 37 km of Elk River, WV, USA. Our understanding of diamond darter habitat use was previously limited, because few individuals have been observed during sampling with conventional gears. We quantified microhabitat use of diamond darters based on measurements of water depth, water velocity and per cent substrate composition. Using spotlights at night‐time, we sampled 16 sites within the lower 133 km of Elk River and observed a total of 82 diamond darters at 10 of 11 sampling sites within the lower 37 km. Glides, located immediately upstream of riffles, were the primary habitats sampled for diamond darters, which included relatively shallow depths (<1 m), moderate‐to‐low water velocities (often < 0.5 m·s^?1) and a smooth water surface. Microhabitat use (mean ± SE) of diamond darters was estimated for depth (0.47 ± 0.02 m), average velocity (0.27 ± 0.01 m·s^?1) and bottom velocity (0.15 ± 0.01 m·s^?1). Substrate used (mean ± SE) by diamond darters was predominantly sand intermixed with lesser amounts of gravel and cobble: % sand (52.1 ± 1.6), % small gravel (12.2 ± 0.78), % large gravel (14.2 ± 0.83), % cobble (19.8 ± 0.96) and % boulder (1.6 ± 0.36). Based on our microhabitat use data, conservation and management efforts for this species should consider preserving glide habitats within Elk River. Spotlighting, a successful sampling method for diamond darters, should be considered for study designs of population estimation and long‐term monitoring.     

Beneficial effects of n-3HUFA enriched Artemia as food for larval palmetto bass (Morone saxatilis × M. chrysops)

The beneficial effects of feeding n−3 highly unsaturated fatty acids (HUFA ≥ 20 carbon fatty acids with three or more double bonds) to palmetto bass (striped bass × white bass) larvae, 4–30 days of age, were studied using Artemia diets enriched with six n-3HUFA levels. Dietary n-3HUFA concentrations were < 0.03% (control diet), 0.33%, 0.63%, 0.87%, 1.26%, and 2.27% of dry-wt Artemia. Larval n-3HUFA contents were reduced at a faster rate with decreasing dietary n-3HUFA intake, and were significantly different by 30 days posthatch (4–20 mg g⁻¹ dry-wt fish). Starved larvae selectively conserved endogenous n-3HUFA reserves, indicating an essential role of n-3HUFA in larval development. Mass mortality in the control and 0.33% n-3HUFA diets occurred at metamorphosis (26–28 days posthatch). At harvest, all fish, except those fed the two highest n-3HUFA diets, suffered from handling stress (shock syndrome) with increasing severity (25 to 100%) at decreasing dietary n-3HUFA intake. Recovery from shock syndrome was 100% at the 0.63% and 0.87% n-3HUFA diets, 63% at the 0.33% n-3HUFA diet and 0% at the control diet. Post-harvest survival was similar among the four highest dietary n-3HUFA groups (64–73%), whereas the two lowest n-3HUFA groups differed significantly (0 and 37%). Growth promotion was evident with increased dietary n-3HUFA intake as fish fed the highest n-3HUFA diet were twice the size of those fed the control diet (99 vs 52 mg wet-wt). Final fish sizes at the three highest n-3HUFA diets were similar. Given similar culture conditions, a minimum dietary n-3HUFA intake of 1.26% of dry-wt Artermia is recommended to avoid handling stress and promote growth in larval palmetto bass.     

The relative contributions of yield components to lint yield of upland cotton,Gossypium hirsutum L.

Summary Stepwise regression analyses provided an estimate of the net effect of yield components on lint yield of Upland cotton. Data from strain tests in the Pee Dee, South Carolina, cotton breeding program for crop years 1968 and 1969 were used in these analyses. Lint yield/m² was the dependent variable. Independent variables were: bolls/m², lint/seed, and seeds/boll.Correlation analyses indicated the relationships among yield components. Partial correlation coefficients were utilized to show the order of variable addition in the regression equations. We found that bolls/m² assumes the major role in determining yield. The lint/seed component assmes the secondary role in the development of lint yield. Seeds/boll made a relatively larger total contribution only after lint/seed had made its contribution.These data indicate that selection pressure should be placed on prolificacy (bolls/m²) and seeds/boll, concommitantly with selection to maintain or increase lint/seed. Although the lint/seed component makes a relatively smaller total contribution to lint yield, it is necessary to maintain or increase this component to secure the increased contributions of seeds/boll.Cooperative investigations of the Plant Science Research Division, Agricultural Research Service, US Department of Agriculture and the Tennessee and South Carolina Agricultural Experiment Stations. South Carolina Technical Contribution No 954.     

Reproductive Behavior of Hexaploid/Diploid Wheat Hybrids 1

The bottleneck restricting introgression of useful genes directly from diploid into hexaploid wheats is the low number of BC₁F₁ seeds obtained. In crosses between hexaploid wheat (Triticum aestivum L.; AABBDD) and Aegilops squarrosa L. (DD) or T. urartu Thum. (AA), this bottleneck may be overcome simply by pollinating a sufficient number of F₁ spikes. However, hybrids between hexaploid wheat cultivars (T. aestivum) and T. monococcum L. (AA) generally are highly female-sterile, often having no pistils. One T. monococcum accession, PI 355520, when crossed with T. aestivum, produced hybrids with female fertility in the same range as that of T. aestivum/A. squarrosa or T. aestivum/T. urartu hybrids, ca. 0.5 to 1.0 backcross seed per spike. We found that female fertility was controlled by two duplicate genes in PI 355520, and that this accession can be used as a bridging parent to introgress genes from other T. monococcum accessions into hexaploid wheat. Pairing of homologous chromosomes was less frequent and weaker in such crosses than in T. aestivum/A. squarrosa crosses, but homoeologous bivalents occurred at a rate of almost 0.5 II per cell. Restitution division was detected in crosses involving all three diploid species and was confirmed cytologically in crosses with PI 355520. Chromosome numbers of BC₁F₁ plants ranged from 35 to 67; plants with 49 or more chromosomes occurred at frequencies of 0.09 to 0.21 among progeny of A. squarrosa and T. urartu and 0.29 in progeny of T. aestivum/T. monococcum crosses involving PI 355520. These results are consistent with those of previous studies, demonstrating the potential of direct Hexaploid/diploid crosses for rapidly introgressing useful genes into Hexaploid wheat with minimum disturbance of the background genotype.     

Gynogen Production in Hybrid Striped Bass

Abstract.— Meiotic gynogens were produced using hybrid striped bass (♀ white bass, Morone chrysops , ×♂ striped bass, M. saxatilis ) eggs and white perch M. americana UV-irradiated sperm. Diploidy of the fertilized eggs was restored by application of hydrostatic pressure, which induced retention of the second polar body. Use of white perch sperm provided an unmistakable marker for detection of a paternal genetic contribution. Two assays were developed using the polymerase chain reaction (PCR) to amplify specific regions of the Morone genome . Primers for gene amplification were developed based on the DNA sequence of the striped bass growth hormone gene (SB-GH) or an anonymous striped bass locus (SBI-10). Control experiments using DNA from the three Morone species demonstrated that gene amplification yielded species-specific patterns of DNA fragments for both of these loci. Therefore, any progeny with a paternal contribution of a set of white perch chromosomes could be identified. Using these assays, we demonstrated that greater than 75% of the progeny obtained from successful experiments were true gynogens. These striped bass hybrid gynogens will provide the basis for future efforts to calculate gene-centromere distances and to identify markers linked to specific traits of interest to aquaculture.     

Comparative Stress Dynamics of Brood Stock Striped Bass Morone saxatilis Associated with Two Capture Techniques

Mature striped bass ( Morone saxatilis ) were collected from the spawning reaches of the Choptank River, Maryland for the purpose of evaluating stress effects associated with capture. Two commonly used capture devices were evaluated—gillnetting and electrofishing. Results indicated that stress, as measured by changes in plasma corticosteroid and chloride concentrations, was significantly lower and recovery time quicker in those fish captured by electrofishing compared to gillnetting. By the end of the study period (48 h), those fish captured by electrofishing had recovered from the initial capture shock as evidenced by corticosteroid levels returning to near baseline levels. Conversely, at 48 h post-capture, those fish captured by gillnetting exhibited severe hypochloremia and elevated corticosteroid levels approaching that of the initial stress associated with capture.     

Iridium-192 interstitial brachytherapy as adjunctive treatment for canine cutaneous mast cell tumors

Eleven dogs with cutaneous mast cell tumors (MCTs) were treated with surgery and iridium-192 ((192)Ir) interstitial brachytherapy. Minimum tumor doses ranged from 47.2 to 63.3 Gy. Treated tumors were classified as grade II (n=7) or III (n=4). Five dogs had recurrences with a median progression-free interval of 1391 days, and six dogs had no recurrence at a median follow-up time of 942 days. Acute adverse effects were well tolerated, and late effects were mild. One dog developed a second tumor of a different cell type in the radiation treatment field.