scholarly journals Getting rid of rain and stars: mitigating inhibition effects in ddPCR assays, the case of the invasive crayfish Pacifastacus leniusculus in the streams of Luxembourg

2021 ◽  
Vol 4 ◽  
Author(s):  
David Porco ◽  
Sylvie Hermant ◽  
Chanistya Purnomo ◽  
Mario Horn ◽  
Guy Marson ◽  
...  
Keyword(s):  
Partial Resistance ◽  
Pacifastacus Leniusculus ◽  
Pcr Inhibition ◽  
Threshold Method ◽  
Low Concentration ◽  
Emulsion Pcr ◽  
Invasive Crayfish ◽  
High Fluorescence ◽  
Double Threshold

ddPCR is getting more and more popular in the field of eDNA-based aquatic monitoring. Even if emulsion PCR used in ddPCR confers a partial resistance to inhibition due to the high number of reactions for the same sample (between 10K and 20K), it is not impervious to it. Inhibition impacts the fluorescence amplitude of positive droplets, affecting both their dispersion and their position relatively to the negative droplets cloud. This fluctuation could jeopardize the use of a shared threshold among several samples and thus the objective assignation of the positive droplets. This is even more critical for low concentration samples such as eDNA samples: the positive droplets are scarce and it is thus crucial to objectively discriminate if they can be counted as positive by establishing an appropriate threshold. Another issue is the artifactual generation of high fluorescence droplets that could be counted as positive with a single threshold solution. Here we propose a double threshold method to take both high fluorescence droplets and PCR inhibition impact into account allowing for an objective sorting of the positive and negative droplets in ddPCR assays.

scholarly journals Size-mediated, density-dependent cannibalism in the signal crayfish Pacifastacus leniusculus (Dana, 1852) (Decapoda, Astacidea), an invasive crayfish in Britain

Crustaceana ◽  
2017 ◽  
Vol 90 (4) ◽  
pp. 417-435 ◽  
Author(s):  
R. J. Houghton ◽  
C. Wood ◽  
X. Lambin
Keyword(s):  
Relative Size ◽  
Pacifastacus Leniusculus ◽  
Gut Contents ◽  
Size Distributions ◽  
Signal Crayfish ◽  
Density Dependent ◽  
Invasive Crayfish ◽  
The Relationship ◽  
Best Fit

The role of cannibalism in crayfish populations is not well understood, despite being a potentially key density-dependent process underpinning population dynamics. We studied the incidence of cannibalism in an introduced signal crayfish Pacifastacus leniusculus population in a Scottish lowland river in September 2014. Animals were sampled using six different sampling techniques simultaneously, revealing variable densities and size distributions across the site. Cannibalism prevalence was estimated by analysing the gut contents of crayfish >20 mm CL for the presence of crayfish fragments, which was found to be 20% of dissected individuals. When seeking evidence of relationships between the sizes of cannibals and ‘prey’, the density of conspecifics <56% the size of a dissected individual yielded the best fit. The relationship between cannibalism probability and crayfish size and density was equally well described by three different metrics of crayfish density. Cannibalism increased with crayfish size and density but did not vary according to sex. These results suggest that large P. leniusculus frequently cannibalize smaller (prey) conspecifics, and that the probability of cannibalism is dependent upon the relative size of cannibal-to-prey and the density of the smaller crayfish. We suggest that removing large individuals, as targeted by many traditional removal techniques, may lead to reduced cannibalism and therefore a compensatory increase in juvenile survival.

Contrast Enhancement Using Optimum Threshold Selection

2020 ◽  
Vol 8 (3) ◽  
pp. 96-118
Author(s):  
Geeta Rani ◽  
Monika Agarwal
Keyword(s):  
Contrast Enhancement ◽  
Maximum Entropy ◽  
Dynamic Range ◽  
Threshold Value ◽  
Histogram Equalization ◽  
Threshold Method ◽  
Essential Information ◽  
Low Contrast ◽  
Brightness Preservation ◽  
Double Threshold

In the recent era, a boom was observed in the field of information retrieval from images. Digital images with high contrast are sources of abundant information. The gathered information is useful in the precise detection of an object, event, or anomaly captured in an image scene. Existing systems do uniform distribution of intensities and apply intensity histogram equalization. These improve the characteristics of an image in terms of visual appearance. The problem of over enhancement and the increase in noise level produces undesirable visual artefacts. The use of Otsu's single threshold method in existing systems is inefficient for segmenting an image with multiple objects and complex background. Additionally, these are incapable to improve the yield of the maximum entropy and brightness preservation. The aforementioned limitations motivate us to propose an efficient statistical pipelined approach, the Range Limited Double Threshold Weighted Histogram Equalization (RLDTWHE). This approach is an integration of Otsu's double threshold, dynamic range stretching, weighted distribution, adaptive gamma correction, and homomorphic filtering. It provides optimum contrast enhancement by selecting the best appropriate threshold value for image segmentation. The proposed approach is efficient in the enhancement of low contrast medical MRI images and digital natural scene images. It effectively preserves all essential information recorded in an image. Experimental results prove its efficacy in terms of maximum entropy preservation, brightness preservation, contrast enhancement, and retaining the natural appearance of an image.

scholarly journals SI on economic costs of invasions - Feeling the pinch: global economic costs of crayfish invasions and comparison with other aquatic crustaceans

2021 ◽  
Author(s):  
Antonin Kouba ◽  
Francisco J. Oficialdegui ◽  
Ross N. Cuthbert ◽  
Melina Kourantidou ◽  
Josie South ◽  
...  
Keyword(s):  
North America ◽  
Multiple Scales ◽  
Pacifastacus Leniusculus ◽  
Freshwater Crayfish ◽  
Similar Magnitude ◽  
Economic Costs ◽  
Knowledge Gaps ◽  
Signal Crayfish ◽  
Invasive Crayfish ◽  
European Economies

Abstract Despite voluminous literature identifying invasive species impacts, understandings of monetary costs remain limited. Recently, profound impacts have been attributed to invasive crustaceans, but associated monetary costs lack synthesis. Here, we analyse globally reported costs of invasive freshwater crayfish across taxonomic, spatial and temporal descriptors. Moreover, we compare their cost magnitude to other invasive crustaceans — crabs, amphipods and lobsters. Between 2000 and 2020, crayfish caused US$ 1.28 billion in reported costs; the vast majority (95%) attributed to Astacidae (principally the signal crayfish Pacifastacus leniusculus) and the remainder to Cambaridae. According to reports, crayfish costs mostly impacted European economies (US$ 1.23 billion), followed by costs reported for North America and Asia. Despite well-known damages caused by invasive crayfish, costs were unreported elsewhere, highlighting knowledge gaps and challenges in cost quantifications. Invasive crayfish costs increased exponentially in the last two decades, averaging at US$ 61 million per-annum. Invasive crabs caused costs of similar magnitude (US$ 1.25 billion; US$ 53 million per-annum) but were mostly confined to North America (95%). Damage-related costs dominated for both crayfish (83%) and crabs (99%), with management spending lacking. Reported economic impacts from amphipods (US$ 178.8 thousand) and lobsters (US$ 44.6 thousand) were considerably lower. We identify burgeoning economic costs from these invasive groups yet highlight pervasive knowledge gaps at multiple scales. Further cost reporting is required to better-ascertain the true scale of monetary costs caused by invasive aquatic crustaceans.

Double threshold method for mastitis diagnosis based on NIR spectra of raw milk and chemometrics

2009 ◽  
Vol 104 (2) ◽  
pp. 243-249 ◽  
Author(s):  
Hesti Meilina ◽  
Shinichiro Kuroki ◽  
B.M. Jinendra ◽  
Kentarou Ikuta ◽  
Roumiana Tsenkova
Keyword(s):  
Raw Milk ◽  
Threshold Method ◽  
Double Threshold

Prevalence of the crayfish plague, Aphanomyces astaci Schikora, in alien crayfish species in Japan

2020 ◽  
Vol 25 (1) ◽  
pp. 31-37
Author(s):  
Kensuke Kamimura ◽  
Tadashi Kawai
Keyword(s):  
Water Temperature ◽  
Procambarus Clarkii ◽  
Severe Disease ◽  
Pacifastacus Leniusculus ◽  
Infection Prevalence ◽  
Infection Status ◽  
Aphanomyces Astaci ◽  
Invasive Crayfish ◽  
The Relationship ◽  
Crayfish Species

Abstract Crayfish plague is a severe disease of crayfish that is caused by the oomycete Aphanomyces astaci. Two crayfish hosts of this parasite, Procambarus clarkii and Pacifastacus leniusculus, were imported from North America into Japan and were found to be infected with this parasite. Since the endemic Japanese crayfish, Cambaroides japonicus, has a low resistance to the crayfish plague, infection with this parasite will likely lead to crayfish death. Specimens of both invasive crayfish species were collected across Japan and their infection status was examined using a PCR technique. Aphanomyces astaci was detected in all localities and the average infection prevalence was 67%. Additionally, when the signs of melanization were compared with the results from PCR analyses, it suggested that the DNA detection procedure is more reliable than observation of tissue melanization. Moreover, the relationship between prevalence and water temperature in the field was analyzed, indicated that water temperature influenced the prevalence of A. astaci infection.

An improved double-threshold method based on gradient histogram

2004 ◽  
Vol 9 (4) ◽  
pp. 473-476 ◽  
Author(s):  
Yang Shen ◽  
Chen Shu-zhen ◽  
Zhang Bing
Keyword(s):  
Threshold Method ◽  
Double Threshold
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