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At least 919 records · Page 51Linked to original sources

USGS2003

Survival, dispersal, and home-range establishment of reintroduced captive-bred puaiohi, Myadestes palmeri

We monitored the survival, dispersal, and home-range establishment of captive-bred, reintroduced puaiohi Myadestes palmeri, a critically endangered thrush endemic to the island of Kauai. Fourteen captive-bred, juvenile birds were released from hacktowers in January-February 1999 and monitored for 8-10 weeks using radiotelemetry. All 14 birds (100%) survived to 56 days post-release. Two birds (14.3%) dispersed greater than 3 km from release site within 1 day of release. The remaining birds settled within 1 week and established either temporary home-ranges (mean area = 7.9??12.0 ha, range 0.4-31.9) or breeding home-ranges (mean area 1.2??0.34 ha, range 0.8-1.6). Temporary home ranges were abandonded by the beginning of the breeding season, and ultimately 6 of the 14 birds (43%) established breeding home ranges in the release area. The high survival rate bodes well for establishing additional populations through captive breeding and release; however, the 57% dispersal rate out of the target area means that several releases of birds may be necessary in order to repopulate a given drainage. Furthermore, observed dispersal and gene flow between the reintroduced and wild populations have important implications for management of the captive flock. Published by Elsevier Science Ltd.

Biological Conservation↗

USGS2000

Biological characterisation of Sarcocystis neurona isolated from a Southern sea otter (Enhydra lutris nereis)

Sarcocystis neurona was isolated from the brain of a juvenile, male southern sea otter ( Enhydra lutris nereis ) suffering from CNS disease. Schizonts and merozoites in tissue sections of the otter’s brain reacted with anti- S. neurona antiserum immunohistochemically. Development in cell culture was by endopolyogeny and mature schizonts were first observed at 3 days postinoculation. PCR of merozoite DNA using primer pairs JNB33/JNB54 and restriction enzyme digestion of the 1100 bp product with Dra I indicated the organism was S. neurona . Four of four interferon-γ gene knockout mice inoculated with merozoites developed S. neurona -associated encephalitis. Antibodies to S. neurona but not Sarcocystis falcatula , Toxoplasma gondii , or Neospora caninum were present in the serum of inoculated mice. This is the first isolation of S. neurona from the brain of a non-equine host.

International Journal for Parasitology↗

USGS2000

Nanogram quantities of a DNA vaccine protect rainbow trout fry against heterologous strains of infectious hematopoietic necrosis virus

The efficacy of a DNA vaccine containing the glycoprotein gene of infectious hematopoietic necrosis virus (IHNV), a rhabdovirus affecting trout and salmon, was investigated. The minimal dose of vaccine required, the protection against heterologous strains, and the titers of neutralizing antibodies produced were used to evaluate the potential of the vaccine as a control pharmaceutical. Results indicated that a single dose of as little as 1–10 ng of vaccine protected rainbow trout fry against waterborne challenge by IHNV. An optimal dose of 100 ng per fish was selected to assure strong protection under various conditions. Neutralizing antibody titers were detected in fish vaccinated with concentrations of DNA ranging from 5 to 0.01 μg. Furthermore, the DNA vaccine protected fish against a broad range of viral strains from different geographic locations, including isolates from France and Japan, suggesting that the vaccine could be used worldwide. A single dose of this DNA vaccine induced protection in fish at a lower dose than is usually reported in mammalian DNA vaccine studies.

Vaccine↗

USGS1998

Aryl hydrocarbon receptor function in early vertebrates:Inducibility of cytochrome P450 1A in agnathan and elasmobranch fish

The mammalian aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor that controls the expression of cytochrome P450 1A (CYP1A) genes in response to halogenated aromatic hydrocarbons such as 2,3,7,8-tetrachlorodibenzo- p -dioxin (TCDD). The natural ligand and normal physiologic function of this protein are as yet unknown. One approach to understanding AHR function and significance is to determine the evolutionary history of this receptor and of processes such as CYP1A induction that are controlled by the AHR in mammals. In these studies, AHR function was evaluated in representative cartilaginous fish (little skate, Raja erinacea ) and jawless fish (sea lamprey, Petromyzon marinus and Atlantic hagfish, Myxine glutinosa ), using CYP1A induction as a model AHR-dependent response. Treatment of skate with β -naphthoflavone (BNF) caused an 8-fold increase in hepatic ethoxyresorufin O -deethylase (EROD) activity as well as a 37-fold increase in the content of immunodetectable CYP1A protein. Evidence of CYP1A inducibility was also obtained for another cartilaginous fish, the smooth dogfish Mustelus canis . In contrast, hepatic EROD activity was not detected in untreated lamprey nor in lamprey treated with 3,3′,4,4′-tetrachlorobiphenyl (TCB), a potent AHR agonist in teleosts. A possible CYP1A homolog was detected in lamprey hepatic microsomes by one of three antibodies to teleost CYP1A, but expression of this protein was not altered by TCB treatment. CYP1A protein and catalytic activity were measurable in hagfish, but neither was induced after treatment with TCB. These results suggest that the AHR-CYP1A signal transduction pathway is highly conserved in gnathostomes, but that there may be fundamental differences in AHR signaling or AHR-CYP1A coupling in agnathan fish. Agnathan fish such as hagfish and lamprey may be interesting model species for examining possible ancestral AHR functions not related to CYP1A regulation.

Comparative Biochemistry and Physiology, Part C: P↗

USGS2003

Phylogeny of the owlet-nightjars (Aves: Aegothelidae) based on mitochondrial DNA sequence

The avian family Aegothelidae (Owlet-nightjars) comprises nine extant species and one extinct species, all of which are currently classified in a single genus, Aegotheles. Owlet-nightjars are secretive nocturnal birds of the South Pacific. They are relatively poorly studied and some species are known from only a few specimens. Furthermore, their confusing morphological variation has made it difficult to cluster existing specimens unambiguously into hierarchical taxonomic units. Here we sample all extant owlet-nightjar species and all but three currently recognized subspecies. We use DNA extracted primarily from museum specimens to obtain mitochondrial gene sequences and construct a molecular phylogeny. Our phylogeny suggests that most species are reciprocally monophyletic, however A. albertisi appears paraphyletic. Our data also suggest splitting A. bennettii into two species and splitting A. insignis and A. tatei as suggested in another recent paper. ?? 2003 Elsevier Science (USA). All rights reserved.

Molecular Phylogenetics and Evolution↗

USGS2006

Conservation genetics of the endangered Shenandoah salamander (Plethodon shenandoah, Plethodontidae)

The Shenandoah salamander (Plethodon shenandoah) is restricted to three isolated talus outcrops in Shenandoah National Park, VA, USA and has one of the smallest ranges of any tetrapod vertebrate. This species was listed as endangered under the US Endangered Species Act in 1989 over concern that direct competition with the red-backed salamander (Plethodon cinereus), successional habitat changes, and human impacts may cause its decline and possible extinction. We address two issues herein: (1) whether extensive introgression (through long-term hybridization) is present between the two species and threatens the survival of P. shenandoah, and (2) the level of population structure within P. shenandoah. We provide evidence from mtDNA haplotypes that shows no genetic differentiation among the three isolates of P. shenandoah, suggesting that their fragmentation is a geologically recent event, and/or that the isolates are still connected by occasional gene flow. There is also no evidence for extensive introgression of alleles in either direction between P. cinereus and P. shenandoah, which suggests that P. shenandoah may not be in danger of being genetically swamped out through hybridization with P. cinereus.

Animal Conservation↗

USGS2015

Statistical models for the analysis and design of digital polymerase chain (dPCR) experiments

Statistical methods for the analysis and design of experiments using digital PCR (dPCR) have received only limited attention and have been misused in many instances. To address this issue and to provide a more general approach to the analysis of dPCR data, we describe a class of statistical models for the analysis and design of experiments that require quantification of nucleic acids. These models are mathematically equivalent to generalized linear models of binomial responses that include a complementary, log–log link function and an offset that is dependent on the dPCR partition volume. These models are both versatile and easy to fit using conventional statistical software. Covariates can be used to specify different sources of variation in nucleic acid concentration, and a model’s parameters can be used to quantify the effects of these covariates. For purposes of illustration, we analyzed dPCR data from different types of experiments, including serial dilution, evaluation of copy number variation, and quantification of gene expression. We also showed how these models can be used to help design dPCR experiments, as in selection of sample sizes needed to achieve desired levels of precision in estimates of nucleic acid concentration or to detect differences in concentration among treatments with prescribed levels of statistical power.

Analytical Chemistry↗

USGS2022

Brief oil exposure reduces fitness in wild Gulf of Mexico mahi-mahi (Coryphaena hippurus)

The Deepwater Horizon (DWH) disaster released 3.19 million barrels of crude oil into the Gulf of Mexico (GOM) in 2010, overlapping the habitat of pelagic fish populations. Using mahi-mahi ( Coryphaena hippurus )─a highly migratory marine teleost present in the GOM during the spill─as a model species, laboratory experiments demonstrate injuries to physiology and behavior following oil exposure. However, more than a decade postspill, impacts on wild populations remain unknown. To address this gap, we exposed wild mahi-mahi to crude oil or control conditions onboard a research vessel, collected fin clip samples, and tagged them with electronic tags prior to release into the GOM. We demonstrate profound effects on survival and reproduction in the wild. In addition to significant changes in gene expression profiles and predation mortality, we documented altered acceleration and habitat use in the first 8 days oil-exposed individuals were at liberty as well as a cessation of apparent spawning activity for at least 37 days. These data reveal that even a brief and low-dose exposure to crude oil impairs fitness in wild mahi-mahi. These findings offer new perspectives on the lasting impacts of the DWH blowout and provide insight about the impacts of future deep-sea oil spills.

Environmental Science and Technology↗

USGS2022

Exposure to 17α-ethinylestradiol results in differential susceptibility of largemouth bass (Micropterus salmoides) to bacterial infection

Disease outbreaks, skin lesions, mortality events, and reproductive abnormalities have been observed in wild populations of centrarchids. The presence of estrogenic endocrine disrupting compounds (EEDCs) has been implicated as a potential causal factor for these effects. The effects of prior EEDC exposure on immune response were examined in juvenile largemouth bass ( Micropterus salmoides ) exposed to a potent synthetic estrogen (17α-ethinylestradiol, EE2) at a low (EE2 Low , 0.87 ng/L) or high (EE2 High , 9.08 ng/L) dose for 4 weeks, followed by transfer to clean water and injection with an LD 40 dose of the Gram-negative bacteria Edwardsiella piscicida . Unexpectedly, this prior exposure to EE2 High significantly increased survivorship at 10 d post-infection compared to solvent control or EE2 Low -exposed, infected fish. Both prior exposure and infection with E. piscicida led to significantly reduced hepatic glycogen levels, indicating a stress response resulting in depletion of energy stores. Additionally, pathway analysis for liver and spleen indicated differentially expressed genes associated with immunometabolic processes in the mock-injected EE2 High treatment that could underlie the observed protective effect and metabolic shift in EE2 High -infected fish. Our results demonstrate that exposure to a model EEDC alters metabolism and immune function in a fish species that is ecologically and economically important in North America.

Environmental Science and Technology↗

USGS2023

Biological responses of Pacific herring embryos to crude oil are quantifiable at exposure levels below conventional limits of quantitation for PAHs in water and tissues

Pacific herring ( Clupea pallasii ), a cornerstone of marine food webs, generally spawn on marine macroalgae in shallow nearshore areas that are disproportionately at risk from oil spills. Herring embryos are also highly susceptible to toxicity from chemicals leaching from oil stranded in intertidal and subtidal zones. The water-soluble components of crude oil trigger an adverse outcome pathway that involves disruption of the physiological functions of cardiomyocytes in the embryonic herring heart. In previous studies, impaired ionoregulation (calcium and potassium cycling) in response to specific polycyclic aromatic hydrocarbons (PAHs) corresponds to lethal embryolarval heart failure or subtle chamber malformations at the high and low ends of the PAH exposure range, respectively. Sublethal cardiotoxicity, which involves an abnormal outgrowth (ballooning) of the cardiac ventricular chamber soon after hatching, subsequently compromises juvenile heart structure and function, leading to pathological hypertrophy of the ventricle and reduced individual fitness, measured as cardiorespiratory performance. Previous studies have not established a threshold for these sublethal and delayed-in-time effects, even with total (∑)PAH exposures as low as 29 ng/g of wet weight (tissue dose). Here, we extend these earlier findings showing that (1) cyp1a gene expression provides an oil exposure metric that is more sensitive than typical quantitation of PAHs via GC–MS and (2) heart morphometrics in herring embryos provide a similarly sensitive measure of toxic response. Early life stage injury to herring (impaired heart development) thus occurs below the quantitation limits for PAHs in both water and embryonic tissues as a conventional basis for assessing oil-induced losses to coastal marine ecosystems.

Environmental Science and Technology↗

USGS2024

Perfluorohexanesulfonic acid (PFHxS) induces hepatotoxicity through the PPAR signaling pathway in larval zebrafish (Danio rerio)

In recent years, the industrial substitution of long-chain per- and polyfluoroalkyl substances (PFAS) with short-chain alternatives has become increasingly prevalent, resulting in the widespread environmental detection of perfluorohexanesulfonic acid (PFHxS), a short-chain PFAS. However, there remains limited information about the potential adverse effects of PFHxS at environmental concentrations to wildlife. Here, early life stage zebrafish ( Danio rerio ) were exposed to environmentally relevant concentrations of PFHxS to better characterize the adverse effects of PFHxS on aquatic organisms. Nontargeted, transcriptomic analysis revealed potential hepatotoxic effects in exposed larvae, including macrovesicular and microvesicular hepatic steatosis, as well as focal liver necrosis. Morphological, histological, biochemical, and targeted transcript expression profiles further confirmed significant alterations in hepatocellular lesion numbers, liver pathological structures, relative liver size, liver biochemical parameters, and liver function genes. To validate the PPAR-mediated toxicological mechanism identified as an enriched pathway through in silico bioinformatics analysis, we tested the coexposure to an antagonist and PPAR morpholino knockdown. This intervention alleviated PFHxS-induced hepatic effects, including reductions in the levels of aspartate aminotransferase, alanine aminotransferase, total cholesterol, and total triglycerides. Our results demonstrate that environmentally relevant concentrations of PFHxS can impair liver development and function in fish, which could have potential risks to aquatic organisms.

Environmental Science & Technology↗

USGS2025

Tetrabromobisphenol S (TBBPS) causes non-negligible and multigenerational reproductive toxicity in zebrafish

Tetrabromobisphenol S (TBBPS) is one of the most extensively used brominated flame retardants detected in the environment. Despite its widespread presence, the effects of persistent environmental exposure to TBBPS on the reproductive system remain unclear, raising significant health concerns. Here, using the zebrafish ( Danio rerio ) model, we identified significant intergenerational endocrine disruption and reproductive toxicity induced by TBBPS after a life-cycle (150 days) of parental exposure to environmentally relevant concentrations of TBBPS (0.01, 0.1, 1, 10, and 100 μg/L). TBBPS interfered with hormone levels and the expression of genes within the hypothalamic–pituitary–gonadal (HPG) axis in both F0 males and females, leading to reduced embryo quality. The parental transmission of TBBPS also impacted the endocrine and reproductive systems of the F1 fish, including the increase of gonadotropin-releasing hormone 3 neuron numbers, changes in hormone levels, and a decrease in embryo numbers. F2 fish also displayed endocrine disruption, even in the absence of detectable TBBPS residues, evidenced by altered fertilization rates and vitellogenin levels. Together, our findings show that exposure to environmentally relevant concentrations of TBBPS can induce reproductive toxicity that persists across generations, weakening the endocrine system and early growth in offspring by disrupting the HPG axis. These data provide critical insight into the persistent health risks posed by TBBPS.

Environmental Science & Technology↗

USGS2019

Toxicokinetics of imidacloprid-coated wheat seeds in Japanese quail (Coturnix japonica) and an evaluation of hazard

Birds are potentially exposed to neonicotinoid insecticides by ingestion of coated seeds during crop planting. Adult male Japanese quail were orally dosed with wheat seeds coated with an imidacloprid (IMI) formulation at either 0.9 mg/kg body weight (BW) or 2.7 mg/kg BW (~3 and 9% of IMI LD50 for Japanese quail, respectively) for 1 or 10 days. Quail were euthanized between 1 and 24 h post-exposure to assess toxicokinetics. Analysis revealed rapid absorption (1 h) into blood, and distribution to brain, muscle, kidney and liver. Clearance to below detection limits occurred at both dose levels and exposure durations in all tissues within 24 h. Metabolism was extensive, with 5-OH-IMI and IMI-olefin detected at greater concentrations than IMI in tissues and fecal samples. There was no lethality or overt signs of toxicity at either dose level. Furthermore, no evidence of enhanced expression of mRNA genes associated with hepatic xenobiotic metabolism, oxidative DNA damage or alterations in concentrations of corticosterone and thyroid hormones was observed. Application of the toxicokinetic data was used to predict IMI residue levels in liver with reasonable results for some field exposure and avian mortality events. It would appear that some affected species are either consuming larger quantities of seeds or exhibit differences in ADME or sensitivity than predicted by read-across from these data.

Environmental Science & Technology↗

USGS2011

Effects of the antimicrobial sulfamethoxazole on groundwater bacterial enrichment

The effects of “trace” (environmentally relevant) concentrations of the antimicrobial agent sulfamethoxazole (SMX) on the growth, nitrate reduction activity, and bacterial composition of an enrichment culture prepared with groundwater from a pristine zone of a sandy drinking-water aquifer on Cape Cod, MA, were assessed by laboratory incubations. When the enrichments were grown under heterotrophic denitrifying conditions and exposed to SMX, noticeable differences from the control (no SMX) were observed. Exposure to SMX in concentrations as low as 0.005 μM delayed the initiation of cell growth by up to 1 day and decreased nitrate reduction potential (total amount of nitrate reduced after 19 days) by 47% ( p = 0.02). Exposure to 1 μM SMX, a concentration below those prescribed for clinical applications but higher than concentrations typically detected in aqueous environments, resulted in additional inhibitions: reduced growth rates ( p = 5 × 10 −6 ), lower nitrate reduction rate potentials ( p = 0.01), and decreased overall representation of 16S rRNA gene sequences belonging to the genus Pseudomonas . The reduced abundance of Pseudomonas sequences in the libraries was replaced by sequences representing the genus Variovorax . Results of these growth and nitrate reduction experiments collectively suggest that subtherapeutic concentrations of SMX altered the composition of the enriched nitrate-reducing microcosms and inhibited nitrate reduction capabilities.

Environmental Science & Technology↗

USGS2013

Probabilistic analysis showing that a combination of bacteroides and methanobrevibacter source tracking markers is effective for identifying waters contaminated by human fecal pollution

Microbial source tracking assays to identify sources of waterborne contamination typically target genetic markers of host-specific microorganisms. However, no bacterial marker has been shown to be 100% host-specific, and cross-reactivity has been noted in studies evaluating known source samples. Using 485 challenge samples from 20 different human and animal fecal sources, this study evaluated microbial source tracking markers including the Bacteroides HF183 16S rRNA, M. smithii nifH, and Enterococcus esp gene targets that have been proposed as potential indicators of human fecal contamination. Bayes' Theorem was used to calculate the conditional probability that these markers or a combination of markers can correctly identify human sources of fecal pollution. All three human-associated markers were detected in 100% of the sewage samples analyzed. Bacteroides HF183 was the most effective marker for determining whether contamination was specifically from a human source, and greater than 98% certainty that contamination was from a human source was shown when both Bacteroides HF183 and M. smithii nifH markers were present. A high degree of certainty was attained even in cases where the prior probability of human fecal contamination was as low as 8.5%. The combination of Bacteroides HF183 and M. smithii nifH source tracking markers can help identify surface waters impacted by human fecal contamination, information useful for prioritizing restoration activities or assessing health risks from exposure to contaminated waters.

Environmental Science & Technology↗

USGS1997

Population genetic structure of a California endemic Branchiopod, Branchinecta sandiegonensis

Branchinecta sandiegonensis (Crustacea: Anostraca) is a narrow range endemic fairy shrimp discontinuously distributed in ephemeral pools on coastal mesas in San Diego County, USA. Ten populations across the range of the species were subjected to allozyme analysis for eleven loci. The species exhibits low variability (P 95 =9.1–45.5) and one third of the loci tested did not conform to Hardy-Weinberg equilibrium expectations. The species also exhibited a high degree of genetic differentiation between populations. F ST values (fixation index) for most pairs of populations were above 0.25 (0.036–0.889).Low genetic variability and high genetic structure may result from low gene flow and founder effects due to habitat fragmentation and the lack of potential vectors for cyst dispersal. The unpredictable rainfall of the region also creates potential for variable population sizes which could affect structure and variability.

Hydrobiologia↗

USGS2013

Developmental instability of gynodioecious Teucrium lusitanicum

Developmental instability was assessed in two geographical races of Teucrium lusitanicum using morphometric measures of vegetative and reproductive structures. T. lusitanicum is a gynodioecious species. Male sterile (female) individuals showed greater developmental instability at all sites. Plants located inland had higher developmental instability of vegetative characters and lower developmental instability of reproductive characters than coastal plants. These results support the contentions that (1) developmental instability is affected more by the disruption of co-adapted gene complexes than by lower heterozygosity, and (2) different habitat characteristics result in the differential response of vegetative and reproductive structures.

Evolutionary Ecology↗

USGS2001

Geographic variation and genetic structure in Spotted Owls

We examined genetic variation, population structure, and definition of conservation units in Spotted Owls ( Strix occidentalis ). Spotted Owls are mostly non-migratory, long-lived, socially monogamous birds that have decreased population viability due to their occupation of highly-fragmented late successional forests in western North America. To investigate potential effects of habitat fragmentation on population structure, we used random amplified polymorphic DNA (RAPD) to examine genetic variation hierarchically among local breeding areas , subregional groups , regional groups , and subspecies via sampling of 21 breeding areas (276individuals) among the three subspecies of Spotted Owls. Data from 11 variable bands suggest a significant relationship between geographic distance among local breeding groups and genetic distance (Mantel r = 0.53, P < 0.02) although multi-dimensional scaling of three significant axes did not identify significant grouping at any hierarchical level. Similarly, neighbor-joining clustering of Manhattan distances indicated geographic structure at all levels and identified Mexican Spotted Owls as a distinct clade. RAPD analyses did not clearly differentiate Northern Spotted Owls from California Spotted Owls. Among Northern Spotted Owls, estimates of population differentiation (F ST ) ranged from 0.27 among breeding areas to 0.11 among regions. Concordantly, within-group agreement values estimated via multi-response permutation procedures of Jaccard's distances ranged from0.22 among local sites to 0.11 among regions. Pairwise comparisons of F ST and geographic distance within regions suggested only the Klamath region was in equilibrium with respect to gene flow and genetic drift. Merging nuclear data with recent mitochondrial data provides support for designation of an Evolutionary Significant Unit for Mexican Spotted Owls and two overlapping Management Units for Northern and California Spotted Owls.

Conservation Genetics↗