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Results for “Journal of Morphology”

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At least 91 records · Page 5Linked to original sources
USGS2008

Temporal downscaling of decadal sediment load estimates to a daily interval for use in hindcast simulations

In this study we used hydrologic proxies to develop a daily sediment load time-series, which agrees with decadal sediment load estimates, when integrated. Hindcast simulations of bathymetric change in estuaries require daily sediment loads from major tributary rivers, to capture the episodic delivery of sediment during multi-day freshwater flow pulses. Two independent decadal sediment load estimates are available for the Sacramento/San Joaquin River Delta, California prior to 1959, but they must be downscaled to a daily interval for use in hindcast models. Daily flow and sediment load data to the Delta are available after 1930 and 1959, respectively, but bathymetric change simulations for San Francisco Bay prior to this require a method to generate daily sediment load estimates into the Delta. We used two historical proxies, monthly rainfall and unimpaired flow magnitudes, to generate monthly unimpaired flows to the Sacramento/San Joaquin Delta for the 1851-1929 period. This step generated the shape of the monthly hydrograph. These historical monthly flows were compared to unimpaired monthly flows from the modern era (1967-1987), and a least-squares metric selected a modern water year analogue for each historical water year. The daily hydrograph for the modern analogue was then assigned to the historical year and scaled to match the flow volume estimated by dendrochronology methods, providing the correct total flow for the year. We applied a sediment rating curve to this time-series of daily flows, to generate daily sediment loads for 1851-1958. The rating curve was calibrated with the two independent decadal sediment load estimates, over two distinct periods. This novel technique retained the timing and magnitude of freshwater flows and sediment loads, without damping variability or net sediment loads to San Francisco Bay. The time-series represents the hydraulic mining period with sustained periods of increased sediment loads, and a dramatic decrease after 1910, corresponding to a reduction in available mining debris. The analogue selection procedure also permits exploration of the morphological hydrograph concept, where a limited set of hydrographs is used to simulate the same bathymetric change as the actual set of hydrographs. The final daily sediment load time-series and morphological hydrograph concept will be applied as landward boundary conditions for hindcasting simulations of bathymetric change in San Francisco Bay.

California↗
USGS2007

Intertidal sand body migration along a megatidal coast, Kachemak Bay, Alaska

[1] Using a digital video-based Argus Beach Monitoring System (ABMS) on the north shore of Kachemak Bay in south central Alaska, we document the timing and magnitude of alongshore migration of intertidal sand bed forms over a cobble substrate during a 22-month observation period. Two separate sediment packages (sand bodies) of 1–2 m amplitude and ∼200 m wavelength, consisting of well-sorted sand, were observed to travel along shore at annually averaged rates of 278 m/yr (0.76 m/d) and 250 m/yr (0.68 m/d), respectively. Strong seasonality in migration rates was shown by the contrast of rapid winter and slow summer transport. Though set in a megatidal environment, data indicate that sand body migration is driven by eastward propagating wind waves as opposed to net westward directed tidal currents. Greatest weekly averaged rates of movement, exceeding 6 m/d, coincided with wave heights exceeding 2 m suggesting a correlation of wave height and sand body migration. Because Kachemak Bay is partially enclosed, waves responsible for sediment entrainment and transport are locally generated by winds that blow across lower Cook Inlet from the southwest, the direction of greatest fetch. Our estimates of sand body migration translate to a littoral transport rate between 4,400–6,300 m 3 /yr. Assuming an enclosed littoral cell, minimal riverine sediment contributions, and a sea cliff sedimentary fraction of 0.05, we estimate long-term local sea cliff retreat rates of 9–14 cm/yr. Applying a numerical model of wave energy dissipation to the temporally variable beach morphology suggests that sand bodies are responsible for enhancing wave energy dissipation by ∼13% offering protection from sea cliff retreat.

Alaska↗
USGS2008

Secrets in the eyes of Black Oystercatchers: A new sexing technique

Sexing oystercatchers in the field is difficult because males and females have identical plumage and are similar in size. Although Black Oystercatchers (Haematopus bachmani) are sexually dimorphic, using morphology to determine sex requires either capturing both pair members for comparison or using discriminant analyses to assign sex probabilistically based on morphometric traits. All adult Black Oystercatchers have bright yellow eyes, but some of them have dark specks, or eye flecks, in their irides. We hypothesized that this easily observable trait was sex-linked and could be used as a novel diagnostic tool for identifying sex. To test this, we compared data for oystercatchers from genetic molecular markers (CHD-W/CHD-Z and HINT-W/HINT-Z), morphometric analyses, and eye-fleck category (full eye flecks, slight eye flecks, and no eye flecks). Compared to molecular markers, we found that discriminant analyses based on morphological characteristics yielded variable results that were confounded by geographical differences in morphology. However, we found that eye flecks were sex-linked. Using an eye-fleck model where all females have full eye flecks and males have either slight eye flecks or no eye flecks, we correctly assigned the sex of 117 of 125 (94%) oystercatchers. Using discriminant analysis based on morphological characteristics, we correctly assigned the sex of 105 of 119 (88%) birds. Using the eye-fleck technique for sexing Black Oystercatchers may be preferable for some investigators because it is as accurate as discriminant analysis based on morphology and does not require capturing the birds. ??2008 Association of Field Ornithologists.

Journal of Field Ornithology↗
USGS2014

The birth and death of transverse aeolian ridges on Mars

Transverse aeolian ridges (TARs) are small bright windblown deposits found throughout the Martian tropics that stand a few meters tall and are spaced a few tens of meters apart. The origin of these features remains mysterious more than 20 years after their discovery on Mars. This paper presents a new hypothesis, that some of the TARs could be indurated dust deposits emplaced millions of years ago during periods of higher axial obliquity. It suggests that these TARs are primary depositional bed forms that accumulated in place from dust carried by the winds in suspension, perhaps in a manner comparable to antidunes on Earth, and were subsequently indurated and eroded to their current states by eons of sandblasting. It points out examples of modern dust drifts and dune‐like features that appear to have been recently formed by dust accumulating directly onto the surface from atmospheric suspension. It shows how these pristine dust deposits could evolve to explain the range of morphologies of the TARs. Finally, it explains how the known properties of many TARs are consistent with this hypothesis, including their composition, thermal behavior, and distribution.

Journal of Geophysical Research E: Planets↗
USGS2016

Genetic analysis shows that morphology alone cannot distinguish asian carp eggs from those of other cyprinid species

Fish eggs and embryos (hereafter collectively referred to as “eggs”) were collected in the upper Mississippi River main stem (~300 km upstream of previously reported spawning by invasive Asian carp) during summer 2013. Based on previously published morphological characteristics, the eggs were identified as belonging to Asian carp. A subsample of the eggs was subsequently analyzed by using molecular methods to determine species identity. Genetic identification using the cytochrome-c oxidase 1 gene was attempted for a total of 41 eggs. Due to the preservation technique used (formalin) and the resulting DNA degradation, sequences were recovered from only 17 individual eggs. In all 17 cases, cyprinids other than Asian carp (usually Notropis sp.) were identified as the most likely species. In previously published reports, a key characteristic that distinguished Asian carp eggs from those of other cyprinids was size: Asian carp eggs exhibited diameters ranging from 4.0 to 6.0 mm and were thought to be much larger than the otherwise similar eggs of native species. Eggs from endemic cyprinids were believed to rarely reach 3.0 mm and had not been observed to exceed 3.3 mm. However, many of the eggs that were genetically identified as originating from native cyprinids were as large as 4.0 mm in diameter (at early developmental stages) and were therefore large enough to over- lap with the lower end of the size range observed for Asian carp eggs. Researchers studying the egg stages of Asian carp and other cyprinids should plan on preserving subsets of eggs for genetic analysis to confirm morphological identifications.

Upper Mississippi River↗
USGS2008

Wolf body mass cline across Minnesota related to taxonomy?

Recent genetic studies suggest that in northern Minnesota two species of wolves (Canis lupus L., 1758 or western wolf and Canis lycaon Schreber, 1775 (= Canis rufus Audubon and Bachman, 1851) or eastern wolf) meet and hybridize. However, little morphological information is available about these two types of wolves in Minnesota. We analyzed the mass of 950 female wolves and 1006 males older than 1 year from across northern Minnesota and found that it increased from 26.30 ?? 0.56 kg (mean ?? SE) for females and 30.60 ?? 0.72 kg for males in northeastern Minnesota to 30.01 ?? 0.43 kg for females and 35.94 ?? 0.45 kg for males in northwestern Minnesota (females: r2 = 0.79, P < 0.02; males: r2 = 0.63, P = 0.06). These mass differences add morphological information to the identities of eastern and western wolves and support the view that ranges of the two species meet in Minnesota. ?? 2008 NRC.

Canadian Journal of Zoology↗
USGS2020

Comparison of specimen- and image-based morphometrics in Cisco

Morphometric data from fish are typically generated using one of two methods: direct measurements made on a specimen or extraction of distances from a digital picture. We compared data on 12 morphometrics collected with these two methods on the same collection of Cisco Coregonus artedi from Lake Ontario, North America, to assess the degree of bias in measurements made directly on a specimen- vs. an image-based method. We also assessed the degree of reproducibility within the image-based method by evaluating the amount of variation between different analysts for each morphometric method. Our results indicate specific morphometrics may be more prone to bias across the two methods and between analysts. Four of 12 morphometrics evaluated showed significant deviation from a 1:1 relationship that would be expected if the imaged-based method produced accurate specimen-based measurements. Pelvic fin length and pelvic–anal fin distance had the highest between-analyst variation for image-based landmarks, indicating low reproducibility for these metrics, compared with pectoral fin or total length, which had lower between-analyst variation. Although some morphometric measurements can be accurately obtained with either method, and therefore potentially used interchangeably in studies on Cisco morphology, our findings highlight the importance of considering method bias in morphometric studies that use data collected by different methods.

Journal of Fish and Wildlife Management↗
USGS2013

Linking morphodynamic response with sediment mass balance on the Colorado River in Marble Canyon: issues of scale, geomorphic setting, and sampling design

Measurements of morphologic change are often used to infer sediment mass balance. Such measurements may, however, result in gross errors when morphologic changes over short reaches are extrapolated to predict changes in sediment mass balance for long river segments. This issue is investigated by examination of morphologic change and sediment influx and efflux for a 100 km segment of the Colorado River in Grand Canyon, Arizona. For each of four monitoring intervals within a 7 year study period, the direction of sand-storage response within short morphologic monitoring reaches was consistent with the flux-based sand mass balance. Both budgeting methods indicate that sand storage was stable or increased during the 7 year period. Extrapolation of the morphologic measurements outside the monitoring reaches does not, however, provide a reasonable estimate of the magnitude of sand-storage change for the 100 km study area. Extrapolation results in large errors, because there is large local variation in site behavior driven by interactions between the flow and local bed topography. During the same flow regime and reach-average sediment supply, some locations accumulate sand while others evacuate sand. The interaction of local hydraulics with local channel geometry exerts more control on local morphodynamic response than sand supply over an encompassing river segment. Changes in the upstream supply of sand modify bed responses but typically do not completely offset the effect of local hydraulics. Thus, accurate sediment budgets for long river segments inferred from reach-scale morphologic measurements must incorporate the effect of local hydraulics in a sampling design or avoid extrapolation altogether.

Arizona↗
USGS1995

Influence of fluoride on aluminum toxicity to Atlantic salmon ( Salmo salar )

Atlantic salmon ( Salmo salar ) alevins were exposed to various aluminum (0–4700 μg/L) and four fluoride (0–500 μg/L) concentrations at two pH values (5.5 and 6.5) for 4- and 30-d periods. In the 4-d tests, aluminum with fluoride was less toxic at pH 6.5 than at pH 5.5, whereas without fluoride, pH had no effect. In the 30-d test, mortality in all treatments was 17–21% at pH 5.5, but only 3–7% at pH 6.5. Fish length and weight after 30 d were reduced in all fluoride–aluminum treatments at pH 5.5, but only in the 200-μg/L aluminum without fluoride treatment at pH 6.5. At pH 5.5 and 6.5 without aluminum, histomorphological examinations revealed no abnormalities in gill tissue. However, in aluminum exposure with no fluoride, gill filaments and secondary lamellae were swollen and thickened. Addition of fluoride at pH 6.5 alleviated some gill damage. At pH 5.5 and 200 μg/L aluminum, addition of 100 μg/L fluoride reduced swelling of gill lamellae, but 200 μg/L fluoride did not reduce swelling. Low fluoride concentrations (< 100 μg/L) may reduce gill morphological damage in fish exposed to aluminum in acidic waters, whereas high fluoride concentrations (> 100 μg/L) may not reduce aluminum-induced effects.

Canadian Journal of Fisheries and Aquatic Sciences↗
USGS2003

A new noncalcified dasycladalean alga from the silurian of Wisconsin

Noncalcified thalli, consisting of a narrow main axis with numerous branched hairlike laterals in whorls and a subapical array of undivided clavate laterals, from the Silurian (Llandovery) Brandon Bridge Formation of southeastern Wisconsin , constitute the basis for a new genus and species of dasycladalean alga , Heterocladus waukeshaensis. A relationship within the family Triploporellaceae is indicated by the whorled arrangement of the laterals and the absence of gametophores on mature specimens. A compilation of occurrence data suggests that noncalcified dasyclads, as a whole, were more abundant and diverse during the Ordovician and Silurian than at any other time in their history. The heterocladous thallus architecture of this alga adds to a wide range of morphological variation documented among Ordovician and Silurian dasyclads, the sum of which indicates that Dasycladales underwent a significant evolutionary radiation during the early Paleozoic.

Wisconsin↗
USGS2000

Standardizing the nomenclature of Martian impact crater ejecta morphologies

The Mars Crater Morphology Consortium recommends the use of a standardized nomenclature system when discussing Martian impact crater ejecta morphologies. The system utilizes nongenetic descriptors to identify the various ejecta morphologies seen on Mars. This system is designed to facilitate communication and collaboration between researchers. Crater morphology databases will be archived through the U.S. Geological Survey in Flagstaff, where a comprehensive catalog of Martian crater morphologic information will be maintained.

Journal of Geophysical Research E: Planets↗
USGS2012

Seasat synthetic aperture radar ( SAR) response to lowland vegetation types in eastern Maryland and Virginia

Examination of SEASAT SAR images of eastern Maryland and Virginia reveals botanical distinctions between vegetated lowland areas and adjacent upland areas. Radar returns from the lowland areas can be either brighter or darker than returns from the upland forests. Scattering models and scatterometer measurements predict an increase of 6 dB in backscatter from vegetation over standing water. This agrees with the SCWigital number (DN) increase observed in the digital SEASAT data. The brightest areas in the Chickahominy, Virginia, drainage, containing P. virginica about 0.4 m high, contrast with the brightest areas in the Blackwater, Maryland, marshes, which contain mature loblolly pine in standing water. The darkest vegetated area in the Chickahominy drainage contains a forest of Nyssa aquatica (water tupelo) about 18 m high, while the darkest vegetated area in the Blackwater marshes contains the marsh plant Spartina alterniflora, 0.3 m high. The density, morphology, and relative geometry of the lowland vegetation with respect to standing water can all affect the strength of the return L band signal.

Journal of Geophysical Research - Oceans↗
USGS2011

Patterns of morphological variation amongst semifossorial shrews in the highlands of Guatemala, with the description of a new species (Mammalia, Soricomorpha, Soricidae)

Members of the Cryptotis goldmani group of small-eared shrews (Mammalia, Soricomorpha, Soricidae) represent a clade within the genus that is characterized by modifications of the forelimb that include broadened forefeet, elongated and broadened foreclaws, and massive humeri with enlarged processes. These modifications are consistent with greater adaptation to their semifossorial habits than other members of the genus. The species in this group occur discontinuously in temperate highlands from southern Tamaulipas, Mexico, to Honduras. In Guatemala, there are three species: the relatively widespread Cryptotis goodwini and two species ( Cryptotis lacertosus , Cryptotis mam ) endemic to highland forests in the Sierra de los Cuchumatanes of western Guatemala. Ongoing studies focusing on the relationships of variation in cranial and postcranial skeletal morphology have revealed a fourth species from remnant cloud forest in the Sierra de Yalijux, central Guatemala. In this paper, I describe this new species and characterize its morphology relative to other species in the C. goldmani group and to other species of Cryptotis in Guatemala. In addition, I summarize available details of its habitat and ecology.

Zoological Journal of the Linnean Society↗
USGS2016

Eurytemora carolleeae in the Laurentian Great Lakes revealed by phylogenetic and morphological analysis

In the Laurentian Great Lakes, specimens of Eurytemora have been reported as Eurytemora affinis since its invasion in the late 1950s. During an intensive collection of aquatic invertebrates for morphological and molecular identification in Western Lake Erie in 2012-2013, several specimens of Eurytemora were collected. Analysis of these specimens identified them as the recently described species Eurytemora carolleeae Alekseev and Souissi 2011. This result led us to assess E. carolleeae’s identifying features, geographic distribution and historical presence in the Laurentian Great Lakes in view of its recent description in 2011. Cytochrome oxidase I (COI) DNA sequences of Eurytemora specimens were identified as closer (2 - 4% different) to recently described E. carolleeae than to most E. affinis sequences (14% different). Eurytemora from other areas of the Great Lakes and from North American rivers as far west as South Dakota (Missouri River) and east to Delaware (Christina River) also keyed to E. carolleeae . Morphological analysis of archival specimens from 1962 and from all the Great Lakes was identified as E. carolleeae . Additionally, Eurytemora drawings in previous publications were reassessed to determine if the species was E. carolleeae and are reported here. Additional morphological characters that may distinguish North American E. carolleeae from other taxa are also described. We conclude that E. carolleeae is the correct name for the species of Eurytemora that has inhabited the Great Lakes since its invasion, as established by both morphological and COI sequence comparisons to reference keys and sequence databases in present and archival specimens.

Great Lakes↗
USGS2015

Speculations on colonizing success of the African clawed frog, Xenopus laevis (Pipidae), in California

The African clawed frog has been established in California for over twenty years. During that period, populations have spread to most of the drainage systems in southern California. It is suggested that a suite of contributing factors, including morphological, behavioural, and biochemical predator avoidance strategies, and reproductive and feeding (cannibalism) strategies, have aided in the success of this species in an extralimital situation.

South African Journal of Zoology↗
USGS2003

Probable relationships between the lower Jurassic crocodilomorph trackways Batrachopus and Selenichus: Evidence and implications based on new finds from the St. George area southwestern Utah

The enigmatic ichnogenus Selenichnus (Hitchcock, 1858) from the Lower Jurassic of Massachusetts and Utah may represent poorly preserved, extramorphological examples of Batrachopus . Selenichnus trackways from the St. George area (Utah) are virtually indistinguishable from the type material described by Hitchcock (1858) and Lull (1953) from Massachusetts. However, Selenichnus type specimens from Massachusetts, as well as the material from Utah, suggest a relationship with Batrachopus : The former track morphology appears to transform into the latter as preservational conditions change. The size and gait indicated by the two ichnogenera are similar. The suggested relationship between the two ichnogenera does not alter the fact that there are distinct differences in the morphology of the type specimens. Thus, pending discovery of more material, formal synonymy of the two ichnogenera is not formally proposed.

Utah↗
USGS2000

A genetic evaluation of morphology used to identify harvested Canada geese

Using maximum likelihood estimators (in genetic stock identification), we used genetic markers to evaluate the utility of 2 morphological measures (culmen length and plumage color) to correctly identify groups of hunter-harvested dusky (Branta canadensis occidentalis) and dusky-like Canada geese on the wintering grounds within the Pacific Flyway. Significant levels of genetic differentiation were observed across all sampled breeding sites for both nuclear microsatellite loci and mtDNA when analyzed at the sequence level. The ability to discriminate among geese from these sites using genetic markers was further demonstrated using computer simulations. We estimated contributions from the Copper River Delta, the primary breeding area of dusky Canada geese, to groups of hunter-harvested geese classified as dusky Canada geese on the basis of morphology as 50.6 ?? 10.1(SE)% for females and 50.3 ?? 13.0% for males. We also estimated that 16 ?? 8.1% of females classified as dusky Canada geese on the basis of morphology originated from Middleton Island, Alaska; a locale currently managed as a subpopulation of dusky Canada geese, even though the majority of geese from this area possess a unique mtdna haplotype not found on the Copper River Delta. The use of culmen length and plumage color to identify the origin of breeding populations in the harvest provides conservative criteria for management of dusky Canada geese as individuals of other breeding populations are misassigned as dusky Canada geese and birds of the lighter-plumaged dusky-like group did not appear to originate from, breeding sites of the dusky Canada goose. Our analyses demonstrate that genetic markers can accurately estimate the proportion of genetically differentiated areas that comprise an admixed group, but they also raise questions about the management scale of Pacific Flyway Canada geese (e.g., at the subspecies or breeding population level) and the use of morphological and genetic characteristics to monitor the harvest of different populations within admixed wintering flocks.

Journal of Wildlife Management↗
USGS1978

Morphology of chasma walls, Mars

The landforms developed on the walls of the Valles Marineris system of chasmas are of three major types, which are locally transitional. The most common type is composed of steep spurs and gullies. The dominant process in the formation or modification of this type appears to be the downslope movement of. material under the influence of gravity, resulting in the accumulation of extensive talus deposits. The type is morphologically similar to high, steep terrestrial scarps in desert or alpine environments. The second morphologic type consists of walls dissected by tributary canyons with characteristic V-shaped cross profiles and blunt canyon heads that locally contain lobate deposits. The tributary canyons may be relict features of the time, when the existence of running water was possible on the surface of Mars. The third morphologic type consists of landslide scars forming broad curved or straight recessed sections of chasma wall. This type is accompanied by landslide deposits that form hummocky floors at the base of the recessed sections. The landslides developed at the expense of other wall morphologies. Chains of rimless depressions and craters that parallel the main structural trends of the chasmas are best interpreted as collapse holes. The origin of the chasmas on Mars is conjectural and may have been structural (grabens), but, on the basis of morphologic studies of their walls, it is suggested that most of the present wall configuration is the result of erosional scarp retreat, where erosion follows preestablished structural planes of weakness.

Journal of Research of the U.S. Geological Survey↗