scholarly journals Salinity stress increases the severity of ranavirus epidemics in amphibian populations

2020 ◽  
Vol 287 (1926) ◽  
pp. 20200062 ◽  
Author(s):  
Emily M. Hall ◽  
Jesse L. Brunner ◽  
Brandon Hutzenbiler ◽  
Erica J. Crespi
Keyword(s):  
Salinity Stress ◽  
Negative Relationship ◽  
Environmental Dna ◽  
Transmission Efficiency ◽  
Decay Rates ◽  
Mass Mortality ◽  
Population Declines ◽  
Elevated Salinity ◽  
Chronic Stressor ◽  
Small Change

The stress-induced susceptibility hypothesis, which predicts chronic stress weakens immune defences, was proposed to explain increasing infectious disease-related mass mortality and population declines. Previous work characterized wetland salinization as a chronic stressor to larval amphibian populations. Thus, we combined field observations with experimental exposures quantifying epidemiological parameters to test the role of salinity stress in the occurrence of ranavirus-associated mass mortality events. Despite ubiquitous pathogen presence (94%), populations exposed to salt runoff had slightly more frequent ranavirus related mass mortality events, more lethal infections, and 117-times greater pathogen environmental DNA. Experimental exposure to chronic elevated salinity (0.8–1.6 g l −1 Cl − ) reduced tolerance to infection, causing greater mortality at lower doses. We found a strong negative relationship between splenocyte proliferation and corticosterone in ranavirus-infected larvae at a moderate elevation of salinity, supporting glucocorticoid-medicated immunosuppression, but not at high salinity. Salinity alone reduced proliferation further at similar corticosterone levels and infection intensities. Finally, larvae raised in elevated salinity had 10 times more intense infections and shed five times as much virus with similar viral decay rates, suggesting increased transmission. Our findings illustrate how a small change in habitat quality leads to more lethal infections and potentially greater transmission efficiency, increasing the severity of ranavirus epidemics.

scholarly journals Cryptic infection of a broad taxonomic and geographic diversity of tadpoles by Perkinsea protists

2015 ◽  
Vol 112 (34) ◽  
pp. E4743-E4751 ◽  
Author(s):  
Aurélie Chambouvet ◽  
David J. Gower ◽  
Miloslav Jirků ◽  
Michael J. Yabsley ◽  
Andrew K. Davis ◽  
...  
Keyword(s):  
Phylogenetic Analyses ◽  
Infectious Agent ◽  
Environmental Dna ◽  
The United States ◽  
Small Subunit ◽  
Oceanic Islands ◽  
Emerging Diseases ◽  
Mass Mortality ◽  
Rdna Sequencing ◽  
Sixth Mass Extinction

The decline of amphibian populations, particularly frogs, is often cited as an example in support of the claim that Earth is undergoing its sixth mass extinction event. Amphibians seem to be particularly sensitive to emerging diseases (e.g., fungal and viral pathogens), yet the diversity and geographic distribution of infectious agents are only starting to be investigated. Recent work has linked a previously undescribed protist with mass-mortality events in the United States, in which infected frog tadpoles have an abnormally enlarged yellowish liver filled with protist cells of a presumed parasite. Phylogenetic analyses revealed that this infectious agent was affiliated with the Perkinsea: a parasitic group within the alveolates exemplified byPerkinsussp., a “marine” protist responsible for mass-mortality events in commercial shellfish populations. Using small subunit (SSU) ribosomal DNA (rDNA) sequencing, we developed a targeted PCR protocol for preferentially sampling a clade of the Perkinsea. We tested this protocol on freshwater environmental DNA, revealing a wide diversity of Perkinsea lineages in these environments. Then, we used the same protocol to test for Perkinsea-like lineages in livers of 182 tadpoles from multiple families of frogs. We identified a distinct Perkinsea clade, encompassing a low level of SSU rDNA variation different from the lineage previously associated with tadpole mass-mortality events. Members of this clade were present in 38 tadpoles sampled from 14 distinct genera/phylogroups, from five countries across three continents. These data provide, to our knowledge, the first evidence that Perkinsea-like protists infect tadpoles across a wide taxonomic range of frogs in tropical and temperate environments, including oceanic islands.

scholarly journals Density-dependent changes in effective area occupied for sea-bottom-associated marine fishes

2016 ◽  
Vol 283 (1840) ◽  
pp. 20161853 ◽  
Author(s):  
James T. Thorson ◽  
Anna Rindorf ◽  
Jin Gao ◽  
Dana H. Hanselman ◽  
Henning Winker
Keyword(s):  
Ideal Free Distribution ◽  
Spatial Dynamics ◽  
Negative Relationship ◽  
Strong Relationship ◽  
Effective Area ◽  
Marine Fishes ◽  
Population Declines ◽  
Density Dependent ◽  
Sea Bottom ◽  
Mixed Support

The spatial distribution of marine fishes can change for many reasons, including density-dependent distributional shifts. Previous studies show mixed support for either the proportional-density model (PDM; no relationship between abundance and area occupied, supported by ideal-free distribution theory) or the basin model (BM; positive abundance–area relationship, supported by density-dependent habitat selection theory). The BM implies that fishes move towards preferred habitat as the population declines. We estimate the average relationship using bottom trawl data for 92 fish species from six marine regions, to determine whether the BM or PDM provides a better description for sea-bottom-associated fishes. We fit a spatio-temporal model and estimate changes in effective area occupied and abundance, and combine results to estimate the average abundance–area relationship as well as variability among taxa and regions. The average relationship is weak but significant (0.6% increase in area for a 10% increase in abundance), whereas only a small proportion of species–region combinations show a negative relationship (i.e. shrinking area when abundance increases). Approximately one-third of combinations (34.6%) are predicted to increase in area more than 1% for every 10% increase in abundance. We therefore infer that population density generally changes faster than effective area occupied during abundance changes. Gadiformes have the strongest estimated relationship (average 1.0% area increase for every 10% abundance increase) followed by Pleuronectiformes and Scorpaeniformes, and the Eastern Bering Sea shows a strong relationship between abundance and area occupied relative to other regions. We conclude that the BM explains a small but important portion of spatial dynamics for sea-bottom-associated fishes, and that many individual populations merit cautious management during population declines, because a compressed range may increase the efficiency of harvest.

scholarly journals Long distance (>20 km) downstream detection of endangered stream frogs suggests an important role for eDNA in surveying for remnant amphibian populations

PeerJ ◽  
2021 ◽  
Vol 9 ◽  
pp. e12013
Author(s):  
Cecilia Villacorta-Rath ◽  
Conrad J. Hoskin ◽  
Jan M. Strugnell ◽  
Damien Burrows
Keyword(s):  
Water Samples ◽  
Survey Methods ◽  
Environmental Dna ◽  
Small Population ◽  
Population Declines ◽  
Long Distance ◽  
Amphibian Species ◽  
Filtration Method ◽  
North East ◽  
Water Volumes

Background Globally, amphibian species have suffered drastic population declines over the past 40 years. Hundreds of species are now listed as Critically Endangered, with many of these considered “possibly extinct”. Most of these species are stream-dwelling frogs inhabiting remote, montane areas, where remnant populations are hard to find using traditional surveys. Environmental DNA (eDNA) could revolutionize surveys for ‘missing’ and endangered amphibian populations by screening water samples from downstream sections to assess presence in the upstream catchments. However, the utility of this survey technique is dependent on quantifying downstream detection probability and distances. Methods Here we tested downstream detection distances in two endangered stream frogs (Litoria lorica and L. nannotis) that co-occur in a remote stream catchment in north-east Australia, and for which we know precise downstream distributional limits from traditional surveys. Importantly, the two last populations of L. lorica persist in this catchment: one small (~1,000 frogs) and one very small (~100 frogs). We conducted eDNA screening at a series of sites kilometers downstream from the populations using precipitation from two fixed water volumes (15 and 100 mL) and via water filtering (mean 1,480 L). Results We detected L. nannotis and the small L. lorica population (~1,000 frogs) at most sampling sites, including 22.8 km downstream. The filtration method was highly effective for far-downstream detection, as was precipitation from 100 mL water samples, which also resulted in consistent detections at the far-downstream sites (including to 22.8 km). In contrast, we had limited downstream detection success for the very small L. lorica population (~100 frogs). Discussion The ecological aspects of our study system, coupled with thorough traditional surveys, enabled us to measure downstream eDNA detection distances with accuracy. We demonstrate that eDNA from a small population of approximately 1,000 frogs can be detected as far as 22.8 km downstream from the population. Water filtration is considered best for eDNA detection of rare aquatic species—indeed it was effective in this study—but we also achieved far-downstream detections when precipitating eDNA from 100 mL water samples. Collecting small water volumes for subsequent precipitation in the lab is more practical than filtration when surveying remote areas. Our downstream detection distances (>20 km) suggest eDNA is a valuable tool for detecting rare stream amphibians. We provide recommendations on optimal survey methods.

scholarly journals Salinity Tolerance and Recovery Attributes of Warm-season Turfgrass Cultivars

HortScience ◽  
2019 ◽  
Vol 54 (9) ◽  
pp. 1625-1631 ◽  
Author(s):  
Manuel Chavarria ◽  
Benjamin Wherley ◽  
James Thomas ◽  
Ambika Chandra ◽  
Paul Raymer
Keyword(s):  
Salinity Stress ◽  
Salinity Tolerance ◽  
Vegetation Index ◽  
Normalized Difference Vegetation Index ◽  
Recovery Period ◽  
Warm Season ◽  
Shoot Biomass ◽  
Seashore Paspalum ◽  
Turf Quality ◽  
Elevated Salinity

As population growth places greater pressures on potable water supplies, nonpotable recycled irrigation water is becoming widely used on turfgrass areas including golf courses, sports fields, parks, and lawns. Nonpotable recycled waters often have elevated salinity levels, and therefore turfgrasses must, increasingly, have good salinity tolerance to persist in these environments. This greenhouse study evaluated 10 commonly used cultivars representing warm-season turfgrass species of bermudagrass (Cynodon spp.), zoysiagrass (Zoysia spp.), st. augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze], and seashore paspalum (Paspalum vaginatum Swartz) for their comparative salinity tolerance at electrical conductivity (EC) levels of 2.5 (control), 15, 30, and 45 dS·m–1. Salinity treatments were imposed on the grasses for 10 weeks via subirrigation, followed by a 4-week freshwater recovery period. Attributes, including turf quality, the normalized difference vegetation index (NDVI), canopy firing, and shoot biomass reductions were evaluated before and after salinity stress, as well as after the 4-week freshwater recovery period. Results showed considerable differences in salinity tolerance among the cultivars and species used, with the greatest tolerance to elevated salinity noted within seashore paspalum cultivars and Celebration® bermudagrass. In comparison with growth in 2.5-dS·m–1 control conditions, increased shoot growth and turf quality were noted for many bermudagrass and seashore paspalum cultivars at 15 dS·m–1. However, st. augustinegrass and some zoysiagrass cultivars responded to elevated salinity with decreased growth and turf quality. No cultivars that had been exposed to 30- or 45-dS·m–1 salinity recovered to acceptable levels, although bermudagrass and seashore paspalum recovered to acceptable levels after exposure to 15-dS·m–1 salinity. More severe salinity stress was noted during year 2, which coincided with greater greenhouse temperatures relative to year 1.

scholarly journals Status of some Micronutrients in Different Soils of Gazipur District as Related to Soil Properties and Land Type

1970 ◽  
Vol 44 (4) ◽  
pp. 425-430
Author(s):  
Khadiza Begum ◽  
Israt Jahan ◽  
M Hasibur Rahman ◽  
M Shahjahan Chowdhury ◽  
Syed Fazle Elahi
Keyword(s):  
Soil Properties ◽  
Negative Relationship ◽  
Organic Matter Content ◽  
Matter Content ◽  
Silty Clay ◽  
Clay Loam ◽  
Land Type ◽  
Small Change ◽  
Brahmaputra Floodplain ◽  
Cu And Zn

An investigation was conducted to evaluate the status of micronutrients i.e. Iron, Manganese, Copper and Zinc and their behavior with respect to some general soil properties according to the land type in some soils of Gazipur district. A total of 114 soil samples were collected from different spots of Sripur and Kaliakair upazilas under Gazipur district which is situated in two physiograpic regions: Madhupur tract and Brahmaputra floodplain. Amount of total Fe, Mn, Cu and Zn varied significantly and ranged from 0.1817-0.3375%, 0.0094-0.0754% , 0.0028-0.0089% and 0.0080-0.1216% respectively in Sripur upazila whereas 0.1433-0.4864%, 0.0428-0.0804%, 0.0020-0.0079% and 0.0030-0.0399% in Kaliakair upazila of different land type. The content in the studied areas increases from high land to low land. The textural class in most soils is silty clay loam, silt loam, clay loam, silty clay and clay. The pH was highly acidic to moderately acidic and there was a small change of pH with the land type. Organic matter content showed an increasing trend from high land to low land of the studied soils. A significant and negative correlation observed between pH and total Mn content while other micronutrients (Fe, Cu and Zn) showed non-significant and negative relationship. Total exchangeable bases of some soils of the studied areas have positive significant correlation with micronutrients. Interaction of micronutrients with each other showed significant relationship. Key words: Fe; Mn; Cu; Zn; Madhupur tract; young Brahmaputra floodplain DOI: 10.3329/bjsir.v44i4.4592 Bangladesh J. Sci. Ind. Res. 44(4), 425-430, 2009

Quantification of Environmental DNA (eDNA) Shedding and Decay Rates for Three Marine Fish

2016 ◽  
Vol 50 (19) ◽  
pp. 10456-10464 ◽  
Author(s):  
Lauren M. Sassoubre ◽  
Kevan M. Yamahara ◽  
Luke D. Gardner ◽  
Barbara A. Block ◽  
Alexandria B. Boehm
Keyword(s):  
Marine Fish ◽  
Environmental Dna ◽  
Decay Rates

scholarly journals Impact of soil salinity on the cowpea nodule-microbiome and the isolation of halotolerant PGPR strains to promote plant growth under salinity stress

2019 ◽  
Author(s):  
Salma Mukhtar ◽  
Ann M. Hirsch ◽  
Noor Khan ◽  
Kauser A. Malik ◽  
Ethan A. Humm ◽  
...  
Keyword(s):  
Plant Growth ◽  
Salinity Stress ◽  
Environmental Dna ◽  
16S Rrna Gene Sequencing ◽  
Soil Samples ◽  
Rrna Gene ◽  
Sequencing Analysis ◽  
Cowpea Varieties ◽  
Plant Growth Promoting ◽  
Pgpr Traits

AbstractFour soil samples (SS-1—SS-4) isolated from semi-arid soils in Punjab, Pakistan were used as inocula for cowpea (Vigna unguiculata L.) grown under salinity stress to analyze the composition of bacteria in the rhizosphere and within nodules through cultivation-dependent and cultivation-independent methods. Two cowpea varieties, 603 and the salt-tolerant CB 46, were each inoculated with four different native soil samples, and data showed that plants inoculated with soil samples SS-2 and SS-4 grew better than plants inoculated with soil samples SS-1 and SS-3. Bacteria were isolated from both soils and nodules, and 34 of the 51 original isolates tested positive for PGPR traits in plate assays with many exhibiting multiple plant growth-promoting properties. A number of isolates were positive for all PGPR traits tested. For the microbiome studies, environmental DNA (eDNA) was isolated from SS-1 and SS-4, which represented the extremes of the Pakistan soils to which the plants responded, and by 16S rRNA gene sequencing analysis were found to consist mainly of Actinobacteria, Firmicutes, and Proteobacteria. However, sequencing analysis of eDNA isolated from cowpea nodules established by the trap plants grown in the four Pakistan soils indicated that the nodule microbiome consisted almost exclusively of Proteobacterial sequences, particularly Bradyrhizobium. Yet, many other bacteria including Rhizobium, Mesorhizobium, Pseudomonas, as well as Paenibacillus, Bacillus as well as non-proteobacterial genera were isolated from the nodules of soil-inoculated cowpea plants. This discrepancy between the bacteria isolated from cowpea nodules (Proteobacteria and non-Proteobacteria) versus those detected in the nodule microbiome (Proteobacteria) needs further study.

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