996 resultados para University of Nebraska (Lincoln campus)


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Table of Contents: Least Bell’s Vireos Are Back, page 3 San Joaquin River National Wildlife Refuge hosted totally unexpected residents last year. Managing Ocean Wildlife, page 5 A new agreement should help in managing marine resources. Focus on . . . Endangered Species, pages 10-21 Whether it’s the fastest land mammal or the tiniest mussel, refuges work on behalf of endangered species. Peeping at Peeps, page 24 Shorebirds can be tough to identify. Classroom and fields trips helped.

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Table of Contents: Make Way for Ducklings, page 4 With help from refuge experts, roads and bridges can be built to accommodate wildlife. Katrina Heroes, pages 8-9 Extraordinary diaries from refuge staffers who were there when Katrina came calling. Focus on…Reaching Youth , page 10-15 Refuges give young people a chance to learn art, poetry, native culture, service – and stewardship. Nisqually: Growing and Restoring, page 17 The Outstanding Refuge Plan of 2005 opens the door to the largest estuary restoration project in the Pacific Northwest.

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Table of Contents: After Rehab, Vessel Starts Over in Alaska The latest addition to the Refuge System’s fleet of vessels in Alaska spent much of its life on the wrong side of the law. In Arizona, Refuges Are Oases for Fish Fish in the desert? Yes. At San Bernardino and Leslie Canyon National Wildlife Refuges, protecting fish is in the establishing mission. FOCUS: Marine National Monuments The four marine national monuments are among the Refuge System’s most distinctive components. As such, they present special challenges, rare opportunities and unparalleled beauty. Can You Hear Me Now? Looking for a low-cost way to connect with visitors? Try a cellphone tour. It’s easy to set up.

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A new species of digenean, Microphallus fonti, is described from the red swamp crawfish in Louisiana, USA. It has a small pharynx and a rudimentary gut like M. opacus and possibly related species from crayfishes, but it differs from them by its relatively large male copulatory papilla and a conspicuous metraterm.

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Heterochrony, the change in timing of developmental processes, is thought to be a key process shaping the numerous limb morphologies of tetrapods. Through a delayed offset in digit development, all cetaceans (i.e., whales, dolphins, and porpoises) have evolved supernumary phalanges (hyperphalangy). Moreover, some toothed cetaceans further alter digital morphologies by delayed endochondral and perichondral ossification of individual elements. In the harbor porpoise (Phocoena phocoena), these paedomorphic patterns have created poorly ossified phalangeal elements. However, no studies have addressed this morphology in other porpoise taxa. This study documents the timing of carpal and digital epiphyseal ossification in the poorly studied vaquita (Phocoena sinus) based on radiographs (n = 18) of known-age specimens. Patterns of vaquita manus ossification were compared between other porpoise and delphinid taxa. Adult vaquitas are paedomorphic in carpal, metacarpal, and digital development as they maintain a juvenile ossification pattern relative to that of other porpoise species of equivalent ages. Vaquitas also ossify fewer carpal elements as compared to other porpoise and some delphinid cetaceans, and ossification arrests relative to that of the harbor porpoise. Vaquitas also display sexual dimorphism as females reach a greater body size and display more ossified elements in the manus relative to their paedomorphic male cohorts.

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A virus, tentatively identified as reo-like, occurred concurrently with experimentally-induced Baculovirus penaei (BP) infection in cultured white shrimp larvae Penaeus vannamei. Each shrimp with a reo-like viral infection also had a BP infection, but not all BP-infected shrimp had a reo-like infection. Both viruses occurred in the same tissues and occasionally withln the same cell. The reolike virus developed in epithelial cells of the anterior midgut and in reserve- and fibrillar-cells of the hepatopancreas. The paraspherical and non-enveloped reo-like virions (ca. 50 nm diam.) occurred as unordered aggregates in the cell cytoplasm. Their etiology has not been determined. Reo-like virions may have been introduced along with the BP virus, or, were latent and only manifested due to stress induced by the more pathogenic BP virus.

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The aseptate gregarine Paraophloidina scolecoides n. sp. (Eugregarinorida: Lecudinidae) heavily infected the midgut of cultured larval and postlarval specimens of Penaeus vannamei from a commercial 'seed-production' facility in Texas, USA. It is morphologically similar to P. korotneffi and P. vibiliae, but it can be distinguished from them and from other members of the genus by having gamonts associated exclusively by lateral syzygy. Shrimp acquired the infection at the facility; nauplii did not show any evidence of infection, but protozoea, mysis, and postlarval shrimp had a prevalence and intensity of infection ranging from 56 to 80 % and 10 to >50 parasites, respectively. Infected shrimp removed from the facility to aquaria at another location lost their gamont infection within 7 days When voided from the gut, the gregarine disintegrated in seawater. Results suggest that P. vannamei is an accidental host, although a survey of representative members of the invertebrate fauna from the environment associated with the facility failed to discover other hosts. No link was established between infection and either the broodstock or the water or detritus from the nursery or broodstock tanks.

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The vaquita (Spanish for "little cow"), or Gulf of California harbor porpoise (Phocoena sinus), has the most limited range of any marine cetacean and is probably the rarest. It has been caught incidentally in gill nets set commercially for totoaba (Totoaba macdonaldi), large fish that were over-exploited in the upper Gulf of California until they, too, were endangered. In 1975. the Mexican Government announced a total indefinite closure on fishing for totoaba, Between the time this porpoise was described as new to science (1958) and its listing by the U.S. Fish and Wildlife Service as Endangered (early 1985), the vaquita was known from only 26 confirmed records (partial remains found on beaches) and a few sightings of live animals. (Note: the vernacular name "cochito" was cited when this animal was listed, but biologists have since learned that "vaquita" is the term used by most local fishermen.) The Endangered Species Technical Bulletin story about its listing (see BULLETIN Vol. X No. 2) said the species was on the brink of extinction "if it still exists."

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Gray whales are coastal migratory baleen whales that are benthic feeders. Most of their feeding takes place in the northern Pacific Ocean with opportunistic feeding taking place during their migrations and residence on the breeding grounds. The concentrations of organochlorines and trace elements were determined in tissues and stomach contents of juvenile gray whales that were taken on their Arctic feeding grounds in the western Bering Sea during a Russian subsistence harvest. These concentrations were compared to previously published data for contaminants in gray whales that stranded along the west coast of the US during their northbound migration. Feeding in coastal waters during their migrations may present a risk of exposure to toxic chemicals in some regions. The mean concentration (standard error of the mean, SEM) of Σ PCBs [1400 (130) ng/g, lipid weight] in the blubber of juvenile subsistence whales was significantly lower than the mean level [27 000 (11 000) ng/g, lipid weight] reported previously in juvenile gray whales that stranded in waters off the west coast of the US. Aluminum in stomach contents of the subsistence whales was high compared to other marine mammal species, which is consistent with the ingestion of sediment during feeding. Furthermore, the concentrations of potentially toxic chemicals in tissues were relatively low when compared to the concentrations in tissues of other marine mammals feeding at higher trophic levels. These chemical contaminant data for the subsistence gray whales substantially increase the information available for presumably healthy animals.

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The most significant cetacean trade items until commercial whaling all but ceased in the 1990s (aside from scientific exchanges of tissues etc.) were meat and blubber from baleen whales for human consumption. Since then, live dolphins and 'small' whales for display (and to some extent for research, military use, and 'therapy') have become the most significant cetacean 'products' in international trade. Trade in live cetaceans is presently dominated by bottlenose dolphins (Tursiops spp.), beluga whales (Debhinapterns leucas) and to a lesser extent killer whales (Orcinus orca) (Fisher and Reeves 2005). In the past, most of the dolphins in trade were common bottlenose dolphins (Tursiops truncatus) originating in the United States, Mexico and the Black Sea, but since the 1980s the United States has essentially stopped its capture-for-export activities and in 2001Mexico implemented a moratorium on live-captures. The source countries for dolphins in trade are now geographically diverse, but Cuba and Japan are currently major source nations for common bottlenose dolphins. Russia is the only current source for belugas. Russia and Japan have become the main potential sources for killer whales since Iceland ceased exporting them in the 1980s or early 1990s.

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The recent likely extinction of the baiji (Chinese river dolphin [Lipotes vexillifer]) (Turvey et al. 2007) makes the vaquita (Gulf of California porpoise [Phocoena sinus]) the most endangered cetacean. The vaquita has the smallest range of any porpoise, dolphin, or whale and, like the baiji, has long been threatened primarily by accidental deaths in fishing gear (bycatch) (Rojas-Bracho et al. 2006). Despite repeated recommendations from scientific bodies and conservation organizations, no effective actions have been taken to remove nets from the vaquita’s environment. Here, we address three questions that are important to vaquita conservation: (1) How many vaquitas remain? (2) How much time is left to find a solution to the bycatch problem? and (3) Are further abundance surveys or bycatch estimates needed to justify the immediate removal of all entangling nets from the range of the vaquita? Our answers are, in short: (1) there are about 150 vaquitas left, (2) there are at most 2 years within which to find a solution, and (3) further abundance surveys or bycatch estimates are not needed. The answers to the first two questions make clear that action is needed now, whereas the answer to the last question removes the excuse of uncertainty as a delay tactic. Herein we explain our reasoning.

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In an open letter published last year in the New York Times, 21 distinguished scientists (including three Nobel laureates) criticized Japan's program of scientific research whaling, noting its poor design and unjustified reliance upon lethal sampling. In a recent Forum article in BioScience, Aron, Burke, and Freeman (2002) castigate the letter's signers and accuse them of meddling in political issues without sufficient knowledge of the science involved in those issues.

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Fifty-one slimy sea plumes (Pseudopterogorgia americana Gmelin, 1791) were sampled for caridean shrimps at Guana Island, British Virgin Islands, during one week in July 1992. Sam- pling depth ranged from 3-22 m. Nine species were collected: Hippolyte nicholsoni Chace, 1972; Latreutes sp.; Neopontonides chacei Heard, 1986; Perclimenes cf. patae Heard and Spotte, 1991; Periclimenes cf. pauper Holthuis, 1951; Periclimenes sp.; Pseudocoutierea antillensis Chace, 1972; Tozeuma cf. cornutum Milne Edwards, 1881; and Trachycaris rugosa (Bate, 1888). A total of 1,418 specimens (including fragments) was obtained. The number of shrimp species per gorgonian ranged from 1-5; one gorgonian harbored 156 shrimps. The two predominant species, N. chacei and H. nicholsoni, occupy different mean depths (12.6 and 8.2 m, respectively). Sexual dimorphism assessed with Mann-Whitney U-tests was not apparent in the specimens of N. chacei (P > 0.05), but females of H. nicholsoni were significantly larger than males (P < 0.001). Minimum carapace length (CL, the tip of the rostrum to the posterior dorsal margin of the carapace) at which male N. chacei acquire a single appendix masculina spine is 1.25 mm; male H. nicholsoni can acquire a single spine at 0.9 mm CL. Histological sections of male N. chacei showed that shrimp with 0 or 1 spine are least likely to be mature. Female N. chacei can become ovigerous at 1.9 mm CL and female H. nicholsoni at 1.2 mm CL. The taxonomic status of 5 of the 9 species collected is uncertain.

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Collectively, the observations indicate that the overall warming of the Arctic system continued in 2007. There are some elements that are stabilizing or returning to climatological norms. These mixed tendencies illustrate the sensitivity and complexity of the Arctic System. Atmosphere: Hot spot shifts toward Europe Ocean: North Pole Temperatures at depth returning to 1990s values Sea Ice: Summer extent at record minimum Greenland: Recent warm temperatures associated with net ice loss Biology: increasing tundra shrub cover and variable treeline advance; up to 80% declines in some caribou herds while goose populations double Land: Increase in permafrost temperatures The Arctic Report Card 2007 is introduced as a means of presenting clear, reliable and concise information on recent observations of environmental conditions in the Arctic, relative to historical time series records. It provides a method of updating and expanding the content of the State of the Arctic Report, published in fall 2006, to reflect current conditions. Material presented in the Report Card is prepared by an international team of scientists and is peer-reviewed by topical experts nominated by the US Polar Research Board. The audience for the Arctic Report Card is wide, including scientists, students, teachers, decision makers and the general public interested in Arctic environment and science. The web-based format will facilitate future timely updates of the content.

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The relationship between energy reserves of the penaeid shrimp Penaeus vannamei and Baculovirus penaei, or BP, were investigated in a series of experiments using mysis stage or early postlarval shrimp. Pre-exposure and post-exposure levels of protein and triacylgycerol (TAG) were determined. The effect of pre-exposure protein and TAG levels on susceptibility to BP infections was also investigated by starving a group of shrimp immediately prior to BP exposure. There was no consistent relationship between either pre-exposure or post-exposure protein levels and the percent of shrimp developing patent BP infections. There was, however, a significant positive correlation between TAG levels immediately prior to viral exposure and prevalence of infection 72 h later. Experimental reduction of TAG reserves prior to BP exposure delayed the development of a patent infection. In some, but not all, experiments there was a significant reduction in TAG levels of infected compared with uninfected shrimp 72 h post-exposure. The effect of patent BP infections on host TAG levels was subordinate to fluctuations in TAG content associated with the ontogeny of the hepatopancreas. Results of this study support histological observations that shrimp lipid levels can be altered by baculovirus infections. Furthermore, high levels of energy reserves in the form of TAG are associated with increased susceptibility to BP infection in larval and postlarval shrimp.