A checklist of halacarid and hydrachnid mites (Acari, Halacaridae & Hydrachnidia) associated with sponges (Porifera)

Zootaxa ◽  
2021 ◽  
Vol 5072 (2) ◽  
pp. 101-129
Author(s):  
TAPAS CHATTERJEE
Keyword(s):  
Cryptic Species ◽  
Mite Species ◽  
Developmental Studies ◽  
Freshwater Sponges ◽  
Molecular Sequencing

A compilation of halacarid and hydrachnid mite species found associated with sponges has been carried out based on published records. Altogether 78 halacarid mites species belonging to 15 genera viz. Agaue (9 species), Agauopsis (7 species), Arhodeoporus (1 species), Atelopsalis (1 species), Bradyagaue (1 species), Copidognathus (27 species), Halacarellus (7 species), Halacaropsis (2 species), Halacarus (5 species), Lohmannella (3 species), Maracarus (3 species), Rhombognathides (3 species), Rhombognathus (4 species), Spongihalacarus (1 species), and Thalassarachna (4 species) are reported. Twenty-four hydrachnid mite species belonging to three families viz. Hygrobatidae (2 species), Unionicolidae (20 species) and Pontarachnidae (2 species) are included. Some species of Unionicolidae are mentioned as possible sponge-mite species. Further studies, emphasizing developmental studies of unionicolid mites to get better ideas about associations with freshwater sponges are needed. Molecular sequencing will reveal more cryptic species and improve the quality of re-descriptions of currently recognized species in these sponge associated mites.  

An annotated checklist of the chaetonotidan Gastrotricha from India

Zootaxa ◽  
2021 ◽  
Vol 5027 (3) ◽  
pp. 332-350
Author(s):  
TAPAS CHATTERJEE ◽  
M. ANTONIO TODARO
Keyword(s):  
Sequence Data ◽  
Molecular Sequence Data ◽  
Molecular Sequence ◽  
History Of Research ◽  
High Incidence ◽  
History Of ◽  
Molecular Sequencing ◽  
Annotated Checklist ◽  
Rule Out

India has a long history of research on freshwater and marine Gastrotricha. In more than 110 years of study on Order Chaetonotida, two families consisting of 11 genera and 39 species have been described. Thirty of these species are taxa originally described from other continents, while only nine species (7 freshwater, 2 marine) are only known from India. The large percentage (77%) of so-called cosmopolitan species in India has contributed to the phenomenon known as the “meiofauna paradox”. However, a careful review of the pertaining literature provides a different biogeographical picture of the chaetonotidan fauna of India. Herein we show that the high incidence of European and North American species reported from India is mainly due to a mixture of misidentification and species lumping. In fact, for only 12 species there are enough data that would make the Indian specimens morphological similar to taxa previously reported from Europe and/or North America. However, without the appropriate molecular sequence data for comparison, there is no way to rule out the possibility of cryptic speciation.We conclude that further sampling throughout India and the use of more powerful microscopical techniques (e.g., DIC optics) and molecular sequencing will reveal more species and improve the quality of re-descriptions of those (9 spp.) that so far appear to be endemic to the subcontinent. Here we recommend six species to be excluded from the fauna of India while another 11 species (non endemic to India) should be considered dubitatively present in the Indian fauna.  

scholarly journals Evaluating the boundaries of marine biogeographic regions of the Southwestern Atlantic using halacarid mites (Halacaridae), meiobenthic organisms with a low dispersal potential

2019 ◽  
Author(s):  
Almir R. Pepato ◽  
Teofânia H. D. Vidigal ◽  
Pavel B. Klimov
Keyword(s):  
Cryptic Species ◽  
Sequence Data ◽  
Environmental Parameters ◽  
Reef Fishes ◽  
Mite Species ◽  
Ecological Niches ◽  
Southwestern Atlantic ◽  
Environmental Niche ◽  
Geographic Population ◽  
Cabo Frio

ABSTRACTAimWe evaluated traditional biogeographic boundaries of coastal marine regions in SW Atlantic using DNA sequence data from common, rocky-shore inhabiting, marine mites of the genera Agauopsis and Rhombognathus, family Halacaridae.MethodsWe investigated geographic population genetic structure using CO1 gene sequences, estimated divergence times using a multigene dataset and absolute time-calibrated molecular clock analyses, and performed environmental niche modeling (ENM) of common marine mite species.ResultsAgauopsis legionium has a shallow history (2.01 Ma) with four geographically differentiated groups. Two of them corresponded to the traditional Amazonian and Northeastern ecoregions, but the boundary between the two other groups was inferred at the Abrolhos Plateau, not Cabo Frio. Rhombognathus levigatoides s. lat. was represented by two cryptic species that diverged 7.22 (multilocus data) or 10.01 Ma (CO1-only analyses), with their boundary, again at the Abrolhos Plateau. ENM showed that A. legionium has suitable habitats scattered along the coast, while the two R. levigatoides cryptic species differ considerably in their niches, especially in parameters related to upwelling. This indicates that genetic isolation associated with the Abrolhos Plateau occurred in both lineages, but for the R. levigatoides species complex, ecological niche specialization was also an important factor.Main conclusionsOur study suggests that the major biogeographic boundary in the Southwestern Atlantic lies not at Cabo Frio but at the Abrolhos Plateau. There, two biogeographically relevant factors meet: (i) changes in current directions (which limit dispersal) and (ii) abrupt changes in environmental parameters associated with the South Atlantic Central Waters (SACW) upwelling (offering distinct ecological niches). We suggest that our result represents a general biogeographic pattern because a barrier at the Abrolhos Plateau was found previously for the fish genus Macrodon (phylogeographic data), prosobranch mollusks, ascidians, and reef fishes (community-level data).

Additional tests on the effects of pesticides on cryptic species of blue oat mite (Penthaleus spp.) and the redlegged earth mite (Halotydeus destructor)

2000 ◽  
Vol 40 (5) ◽  
pp. 671 ◽  
Author(s):  
M. T. Robinson ◽  
A. A. Hoffmann
Keyword(s):  
Cryptic Species ◽  
New South ◽  
New South Wales ◽  
Mite Species ◽  
Effective Control ◽  
Individual Species ◽  
Halotydeus Destructor ◽  
Tolerant Species ◽  
South Wales ◽  
Lambda Cyhalothrin

Earth mites (Halotydeus destructor, Penthaleus spp.) are important pests of crops and pastures in southern Australia during the winter and spring. A recent study showed that control of these mites is complicated by different responses of species to several pesticides, with one cryptic species (Penthaleus falcatus) being particularly tolerant. In this study, earth mites were tested against 4 other chemicals registered for mite control (alpha-cypermethrin, phosmet, chlorpyrifos and lambda-cyhalothrin) in an attempt to identify useful pesticides to counter control failures. Furthermore, an isolated population of an undescribed cryptic Penthaleus species (P. sp. x) from northern New South Wales was tested for its response to 8 pesticides. Species responded differently to all pesticides. Halotydeus destructor was usually the least tolerant species except in the case of phosmet where P. major was the least tolerant species. For alpha-cypermethrin and lambda-cyhalothrin, tolerance of all Penthaleusspecies was similar or higher than that of H. destructor. Penthaleus falcatus had a relatively higher tolerance to phosmet than all other species. The response of P. sp. x (New South Wales) to chlorpyrifos was inconsistent between trials and the response of this species to lambda-cyhalothrin was complex. Penthaleus sp. x (New South Wales) was generally more tolerant than H. destructor but not as tolerant as P. falcatus. The results highlight the fact that mite species need to be identified when considering control options and suggest that effective control recommendations need to be developed for each individual species.

scholarly journals Qoala-T: A supervised-learning tool for quality control of automatic segmented MRI data

2018 ◽  
Author(s):  
Eduard T. Klapwijk ◽  
Ferdi van de Kamp ◽  
Mara van der Meulen ◽  
Sabine Peters ◽  
Lara M. Wierenga
Keyword(s):  
Quality Control ◽  
Supervised Learning ◽  
Area Under The Curve ◽  
High Sensitivity ◽  
Poor Quality ◽  
Developmental Studies ◽  
Quality Ratings ◽  
Control Procedures ◽  
Processing Errors

AbstractPerforming quality control to detect image artifacts and data-processing errors is crucial in structural magnetic resonance imaging, especially in developmental studies. Currently, many studies rely on visual inspection by trained raters for quality control. The subjectivity of these manual procedures lessens comparability between studies, and with growing study sizes quality control is increasingly time consuming. In addition, both inter-rater as well as intra-rater variability of manual quality control is high and may lead to inclusion of poor quality scans and exclusion of scans of usable quality. In the current study we present the Qoala-T tool, which is an easy and free to use supervised-learning model to reduce rater bias and misclassification in manual quality control procedures. First, we manually rated quality of N = 784 FreeSurfer-processed T1-weighted scans. Different supervised-learning models were then compared to predict manual quality ratings. Results show that the Qoala-T tool using random forests is able to predict scan quality with both high sensitivity and specificity (mean area under the curve (AUC) = 0.98). In addition, the Qoala-T tool was also able to adequately predict the quality of a novel unseen dataset (N = 112; mean AUC = 0.95). These outcomes indicate that using Qoala-T in other datasets could greatly reduce the time needed for quality control. More importantly, this procedure could further help to reduce variability related to manual quality control, thereby benefiting the comparability of data quality between studies.

Immunoferritin localization of intracellular antigens in positively stained frozen sections

1978 ◽  
Vol 36 (2) ◽  
pp. 168-169
Author(s):  
K. T. Tokuyasu
Keyword(s):  
Surface Tension ◽  
Water Surface ◽  
Thin Layers ◽  
The Other ◽  
Positive Staining ◽  
Frozen Sections ◽  
The Past ◽  
Ultrathin Frozen Sections ◽  
Definition Of

During the past investigations of immunoferritin localization of intracellular antigens in ultrathin frozen sections, we found that the degree of negative staining required to delineate u1trastructural details was often too dense for the recognition of ferritin particles. The quality of positive staining of ultrathin frozen sections, on the other hand, has generally been far inferior to that attainable in conventional plastic embedded sections, particularly in the definition of membranes. As we discussed before, a main cause of this difficulty seemed to be the vulnerability of frozen sections to the damaging effects of air-water surface tension at the time of drying of the sections.Indeed, we found that the quality of positive staining is greatly improved when positively stained frozen sections are protected against the effects of surface tension by embedding them in thin layers of mechanically stable materials at the time of drying (unpublished).

Lithography below 100 nm

1983 ◽  
Vol 41 ◽  
pp. 96-99
Author(s):  
L. D. Jackel
Keyword(s):  
Spatial Distribution ◽  
Electron Beam ◽  
Electron Scattering ◽  
Electron Beam Lithography ◽  
Substrate Material ◽  
Local Electron ◽  
Electron Dose ◽  
Positive Resist ◽  
Exposure Process

Most production electron beam lithography systems can pattern minimum features a few tenths of a micron across. Linewidth in these systems is usually limited by the quality of the exposing beam and by electron scattering in the resist and substrate. By using a smaller spot along with exposure techniques that minimize scattering and its effects, laboratory e-beam lithography systems can now make features hundredths of a micron wide on standard substrate material. This talk will outline sane of these high- resolution e-beam lithography techniques.We first consider parameters of the exposure process that limit resolution in organic resists. For concreteness suppose that we have a “positive” resist in which exposing electrons break bonds in the resist molecules thus increasing the exposed resist's solubility in a developer. Ihe attainable resolution is obviously limited by the overall width of the exposing beam, but the spatial distribution of the beam intensity, the beam “profile” , also contributes to the resolution. Depending on the local electron dose, more or less resist bonds are broken resulting in slower or faster dissolution in the developer.

Convergent Beam Electron Diffraction

1978 ◽  
Vol 36 (3) ◽  
pp. 304-315
Author(s):  
G. Lehmpfuhl
Keyword(s):  
Electron Diffraction ◽  
Diffraction Pattern ◽  
Crystal Surface ◽  
Diffraction Spot ◽  
Crystal Thickness ◽  
Large Area ◽  
Electron Microscopic ◽  
Additional Information ◽  
Microscopic Investigations

Introduction In electron microscopic investigations of crystalline specimens the direct observation of the electron diffraction pattern gives additional information about the specimen. The quality of this information depends on the quality of the crystals or the crystal area contributing to the diffraction pattern. By selected area diffraction in a conventional electron microscope, specimen areas as small as 1 µ in diameter can be investigated. It is well known that crystal areas of that size which must be thin enough (in the order of 1000 Å) for electron microscopic investigations are normally somewhat distorted by bending, or they are not homogeneous. Furthermore, the crystal surface is not well defined over such a large area. These are facts which cause reduction of information in the diffraction pattern. The intensity of a diffraction spot, for example, depends on the crystal thickness. If the thickness is not uniform over the investigated area, one observes an averaged intensity, so that the intensity distribution in the diffraction pattern cannot be used for an analysis unless additional information is available.

Observability of Very Thick Specimen by Using Transmission Scanning Electron Microscope

1971 ◽  
Vol 29 ◽  
pp. 26-27
Author(s):  
K. Shibatomi ◽  
T. Yamanoto ◽  
H. Koike
Keyword(s):  
Electron Microscope ◽  
Image Quality ◽  
Scanning Electron Microscope ◽  
Chromatic Aberration ◽  
Image Contrast ◽  
Objective Lens ◽  
Thick Specimen ◽  
Transmission Electron ◽  
Scanning Electron

In the observation of a thick specimen by means of a transmission electron microscope, the intensity of electrons passing through the objective lens aperture is greatly reduced. So that the image is almost invisible. In addition to this fact, it have been reported that a chromatic aberration causes the deterioration of the image contrast rather than that of the resolution. The scanning electron microscope is, however, capable of electrically amplifying the signal of the decreasing intensity, and also free from a chromatic aberration so that the deterioration of the image contrast due to the aberration can be prevented. The electrical improvement of the image quality can be carried out by using the fascionating features of the SEM, that is, the amplification of a weak in-put signal forming the image and the descriminating action of the heigh level signal of the background. This paper reports some of the experimental results about the thickness dependence of the observability and quality of the image in the case of the transmission SEM.

The Current Situation in Chemical Stabilization of Biological Materials

1972 ◽  
Vol 30 ◽  
pp. 132-133
Author(s):  
John H. Luft
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Osmium Tetroxide ◽  
Molecular Level ◽  
Cross Linking ◽  
Chemical Stabilization ◽  
Specimen Preparation ◽  
Sufficient Condition ◽  
Radio Telescopes

With information processing devices such as radio telescopes, microscopes or hi-fi systems, the quality of the output often is limited by distortion or noise introduced at the input stage of the device. This analogy can be extended usefully to specimen preparation for the electron microscope; fixation, which initiates the processing sequence, is the single most important step and, unfortunately, is the least well understood. Although there is an abundance of fixation mixtures recommended in the light microscopy literature, osmium tetroxide and glutaraldehyde are favored for electron microscopy. These fixatives react vigorously with proteins at the molecular level. There is clear evidence for the cross-linking of proteins both by osmium tetroxide and glutaraldehyde and cross-linking may be a necessary if not sufficient condition to define fixatives as a class.

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