Observations on the honey bee tracheal mite Acarapis woodi (Acari: Tarsonemidae) using low-temperature scanning electron microscopy

Systematic Entomology Laboratory, BARC-West, Bldg. 005, Room 137, Agriculture Research Service, US Department of Agriculture, Henry A. Wallace Beltsville Agricultural Research Center, Beltsville, MD 20705, USA.
Experimental and Applied Acarology (Impact Factor: 1.62). 02/2005; 35(3):239-49. DOI: 10.1007/s10493-004-5080-8
Source: PubMed


Observations were made of cryo-preserved honey bee tracheal mites Acarapis woodi (Rennie) using scanning electron microscopy. We describe various new morphological attributes of A. woodi based on the ability of the cryo-technique to capture live mites in natural positions and observe the Low-Temperature Scanning Electron Microscopy (LT-SEM) photographs under a 3-D viewer. Most striking was the observation that each leg has the ability to independently twist its segments with the ambulacrum rotating a minimum of 180 degrees during locomotion; this is a more sophisticated form of locomotion than has been proposed for the Acari. Adult daughter mites are known to be the dispersal instar moving from the tracheal tube to the thoracic hairs of the bee and then transferring to a new bee. We hypothesize that adult tarsal claws and setae on the legs play a role in attachment to hairs during dispersal. However, our evidence is that none of the life stases use their tarsal claws within the tracheal tubes. Larvae were observed to be 'freely moving' within the tracheal system, their tarsal claws rendered inoperative due to an enlarged swollen pulvillar pad. The solenidia of leg I are now known to have striations and the famulus is bifurcated. The bifurcated famulus, solenidial striations, and segmentation of leg IV of females may have taxonomic implications in the family Tarsonemidae. The body and leg setae of adults appear to be used as a tactile tool to sense the amount of space within the tracheal tubes; most of the setae are oriented distally and may help the mite to measure the space or radius of the tracheal tubes. The modified caudal region of the male revealed remnants of the h1 and h2 setae and a smooth clean surface, void of a film, supporting that pharate nymphs are not attached in this species.

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    • "The details of tracheal morphology can be measured using light and transmission electron microscopy (TEM) of stained or filled tissues (Wigglesworth and Lee, 1982; Schmitz and Perry, 1999; Hartung et al., 2004; Snelling et al., 2011, 2012) or scanning electron microscopy of dissected tracheal tubes (Ochoa et al., 2005) or of plasticine fills of the tracheal system (Maina, 1989). However, these destructive approaches are also technically challenging and time-consuming, limiting their potential spatial coverage and resolution within an insect and making measurements of large numbers of insects impractical. "
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    ABSTRACT: Variation in the morphology of the insect tracheal system can strongly affect respiratory physiology, with implications for everything from pest control to evolution of insect body size. However, the small size of most insects has made measuring the morphology of their tracheal systems difficult. Historical approaches including light microscopy and scanning and transmission electron microscopy (SEM, TEM) are technically difficult, labor intensive, and can introduce preparation artifacts. More recently, synchrotron X-ray microtomography (SR-μCT) has allowed for detailed analysis of tracheal morphology of diverse insects. However, linear accelerators required for SR-μCT are not readily available, making the approach unavailable for most labs. Recent advancements in microcomputed tomography (μCT) have made possible fine resolution of internal morphology of very small insects. However, μCT has never been used to quantify insect tracheal system dimensions. We measured respiratory volume of a grasshopper (Schistocerca americana) by analysis of high resolution μCT scans. Volume estimates from μCT closely matched volume estimates by water displacement as well as literature estimates for this species. The μCT approach may thus provide a widely available, cost-effective, and straightforward approach to characterizing the internal morphology of insect respiratory systems.
    Arthropod structure & development 09/2013; 42:437-442. DOI:10.1016/j.asd.2013.06.003 · 1.65 Impact Factor
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    • "Various applications have been reported, and the usefulness has been widely shown in identification of new species, analysis of antiparasitic drugs, host-infection interaction, etc. [1]–[7]. Recent applications of low-temperature SEM analysis enabled observation of new morphological attributes and proposed a new model of leg locomotion [8], [9]. However, these observations did not involve living organisms or real movements. "
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    ABSTRACT: Scanning electron microscopes (SEM), which image sample surfaces by scanning with an electron beam, are widely used for steric observations of resting samples in basic and applied biology. Various conventional methods exist for SEM sample preparation. However, conventional SEM is not a good tool to observe living organisms because of the associated exposure to high vacuum pressure and electron beam radiation. Here we attempted SEM observations of live ticks. During 1.5×10(-3) Pa vacuum pressure and electron beam irradiation with accelerated voltages (2-5 kV), many ticks remained alive and moved their legs. After 30-min observation, we removed the ticks from the SEM stage; they could walk actively under atmospheric pressure. When we tested 20 ticks (8 female adults and 12 nymphs), they survived for two days after SEM observation. These results indicate the resistance of ticks against SEM observation. Our second survival test showed that the electron beam, not vacuum conditions, results in tick death. Moreover, we describe the reaction of their legs to electron beam exposure. These findings open the new possibility of SEM observation of living organisms and showed the resistance of living ticks to vacuum condition in SEM. These data also indicate, for the first time, the usefulness of tick as a model system for biology under extreme condition.
    PLoS ONE 08/2012; 7(3):e32676. DOI:10.1371/journal.pone.0032676 · 3.23 Impact Factor
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    • "The preparation of samples for cryo-SEM followed that described by Ochoa et al. (2005) and Kumar et al. (2001) with some modifications. Mite samples were quickly submerged into liquid nitrogen slush at −196°C for freezing. "
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    ABSTRACT: Samples of Mimolette (France) and Milbenkase (Germany) cheeses traditionally ripened by mites were analyzed to determine the mite species present on each sample. Scientific literature was reviewed to understand which mite species most commonly infest cheese. Morphological features possessed by mites were then studied to understand what unique characteristics are required to ensure accurate identification. After identification and compilation of a detailed key of stored food mites (subclass Acari, order Astigmata) and their delineating features, the mites were viewed through a cryogenic scanning electron microscope. It was determined that Mimolette cheese is inoculated with Acarus siro L. The features studied to identify this mite species included idiosomal length and shape, setae length and arrangement, leg size, placement of anus and genitals, and solenidia shape. The Milbenkase cheese is inoculated with Tyrolichus casei Oudemans, which was evident after viewing the same features used to identify A. siro and the supracoxal seta shape. With this knowledge, further research can be conducted on the 2 cheese varieties to understand what chemical, physical, and microbial changes occur within the cheeses because of mites. It is important to identify the mite species present on each cheese variety to improve our understanding of their role in creating the distinctive characteristics that set these cheeses apart from others.
    Journal of Dairy Science 08/2010; 93(8):3461-8. DOI:10.3168/jds.2009-2937 · 2.57 Impact Factor
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