Observations on the coiled posture of trichostrongyle infective larvae using a freeze-substitution method and scanning electron microscopy

Wharton, David A.

doi:10.1016/0020-7519(82)90037-6

Cited by 11 publications

(14 citation statements)

References 20 publications

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“…Factors thought to trigger coiling in nematodes include the restriction of lateral movement as their habitat dries out (Wharton, 1981) and rise in temperature (Wharton, 1982). In our study, all nematodes tested except H. bacteriophora initially showed some tendency to coil, and became immobile over time.…”

Section: Discussionmentioning

confidence: 95%

The effect of osmotic stress on desiccation survival and water content of four nematode species

Charwat¹,

Fisher²,

Wyss³

2002

Nematol

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The effects of osmotic stress on water loss and subsequent desiccation survival of Anguina funesta second stage juveniles (J2), Rhabditis strongyloides (J2-J4), Aphelenchus avenae (J2-adult) and Heterorhabditis bacteriophora (J3) were investigated by incubating nematodes in sucrose gradients before exposure to 0% relative humidity (RH). Survival of A. funesta J2 was unaffected by osmotic stress and subsequent desiccation and juveniles seemed pre-adapted to both forms of dehydration. Heterorhabditis bacteriophora showed high tolerance to osmotic stress but all J3 were killed by exposure to 0% RH. Pre-exposure to osmotic stress improved desiccation tolerance in R. strongyloides and A. avenae but the stress levels that induced protective adaptations against desiccation were different for each species. Osmotically induced water loss was rapid in all four species and nematodes reached equilibrium after 4-12 h, their nal water content being dictated by the osmotic pressure of the medium. A unique mechanism of osmotic adaptation occurred in R. strongyloides J2-J4 allowing juveniles to regain their initial hydration level.

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Section: Discussionmentioning

confidence: 95%

The effect of osmotic stress on desiccation survival and water content of four nematode species

Charwat¹,

Fisher²,

Wyss³

2002

Nematol

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“…Some species have extremely low cuticular permeabilities and will still be swimming around in chemical fixatives after several hours. Techniques which have been used include air drying from solvents, infiltration with glycerol or resin, freeze drying and critical point drying after chemical fixation (Wharton, 1982;Eisenback, 1986). Chemical fixation requires the use of hot or cold fixatives and usually involves cutting the specimen.…”

Section: Introductionmentioning

confidence: 99%

“…Freeze substitution has been used extensively to prepare biological material for 187 0 1991 The Royal Microscopical Society examination by transmission electron microscopy and X-ray microanalysis (Robards & Sleytr, 1985), but has been rarely used for SEM. Cohen (1974) briefly described a technique for preparing small arthropods for SEM by freeze substitution, and this method has proved successful with nematodes, dipteran larvae, nematophagous fungi, plant tissues, yeast and the cilia of molluscs and protozoa (Robards, 1978;Barlow & Sleigh, 1979;Wharton, 1982;Colwell & Kokko, 1986;Muller, 1988;Wharton & Murray, 1990). Wharton (1982) compared various techniques for preparing the infective juveniles of the nematode Trichostrongylus colubriforrnis for SEM.…”

Section: Introductionmentioning

confidence: 99%

“…Cohen (1974) briefly described a technique for preparing small arthropods for SEM by freeze substitution, and this method has proved successful with nematodes, dipteran larvae, nematophagous fungi, plant tissues, yeast and the cilia of molluscs and protozoa (Robards, 1978;Barlow & Sleigh, 1979;Wharton, 1982;Colwell & Kokko, 1986;Muller, 1988;Wharton & Murray, 1990). Wharton (1982) compared various techniques for preparing the infective juveniles of the nematode Trichostrongylus colubriforrnis for SEM. Freeze substitution proved superior to the other techniques used, including chemical fixation, resulting in good surface preservation, little collapse and the retention of the coiled posture exhibited by these nematodes.…”

Section: Introductionmentioning

confidence: 99%

“…Freeze drying after a sequential fixation in glutaraldehyde gave the best result, but freeze substitution was not tested. Wharton (1982) tested a variety of substitution media and obtained the best results using methanol. Methanol also seems to be the best choice of substitution medium due to its physical characteristics.…”

Section: Introductionmentioning

confidence: 99%

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Freeze‐substitution techniques for preparing nematodes for scanning electron microscopy

Wharton¹

1991

Journal of Microscopy

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SUMMARY The effect of different substitution times, temperatures and the incorporation of fixatives on the preservation of three species of nematode for scanning electron microscopy by freeze substitution with methanol, followed by critical point drying, is investigated. Hammerschmidtiella diesingi adults and Trichostrongylus colubriformis infective juveniles were successfully preserved using methanol at 253 K as the substitution medium. Preservation deteriorated with long substitution times, suggesting the extraction of material and that substitution times should be kept as brief as possible. Panagrolaimus davidi was not successfully preserved using pure methanol, but preservation was improved by using fixatives in the substitution medium, the best results being obtained with 1% OsO4/3% glutaraldehyde in methanol. A substitution temperature of 193 K did not give any improvement in preservation. The differences in the quality of preservation between the three species may be due to the relative ability of the cuticle to withstand collapse during critical point drying. Chemical fixation using cold fixative resulted in the retention of a natural posture but poor preservation, whereas hot fixatives resulted in good preservation but the loss of a natural posture. Freeze substitution in methanol may prove useful in the preparation of specimens possessing cuticles or cell walls which have sufficient strength to withstand the drying process (e.g. arthropods, plants, fungi, nematodes). More delicate specimens may require the incorporation of fixatives into the substitution medium or conventional fixation.

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Aggregation effects on anhydrobiotic survival in the tardigrade Richtersius coronifer

Ivarsson¹,

Jonsson²

2004

J. Exp. Zool.

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For anhydrobiotic metazoans the rate of desiccation is an important factor influencing the probability of survival in a dry anhydrobiotic state. Formation of animal aggregations, in which the exposed body surface area of individual animals is reduced, represents one way to reduce the rate of evaporation. Such aggregations have earlier been documented in e.g., nematodes. We experimentally evaluate the effect of aggregation size (number of animals in a group of desiccating animals) on anhydrobiotic survival in the eutardigrade Richtersius coronifer. The experiment shows that aggregation provides a clear improvement on anhydrobiotic survival. The most likely explanation for this is that aggregated animals were exposed to a lower rate of desiccation. Although the empirical evidence of aggregation in tardigrades is scarce, our study suggests that aggregation could potentially be an important survival factor for tardigrades living in environments characterized by periods of rapid desiccation.

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Observations on the coiled posture of trichostrongyle infective larvae using a freeze-substitution method and scanning electron microscopy

Cited by 11 publications

References 20 publications

The effect of osmotic stress on desiccation survival and water content of four nematode species

The effect of osmotic stress on desiccation survival and water content of four nematode species

Freeze‐substitution techniques for preparing nematodes for scanning electron microscopy

Aggregation effects on anhydrobiotic survival in the tardigrade Richtersius coronifer

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