FNZ 7 - Cryptostigmata (Arachnida: Acari) - Techniques
Luxton, M 1985. Cryptostigmata (Arachnida: Acari) - a concise review. Fauna of New Zealand 7, 112 pages.
(
ISSN 0111-5383 (print),
;
no.
07.
ISBN 0-477-06762-X (print),
).
Published 08 Dec 1985
ZooBank: http://zoobank.org/References/98C34746-C9D1-4CD1-8FD4-1115A3FAAFAB
Techniques
Collection
Many cryptostigmatids may be collected directly by using a fine, moistened artist's brush or a 'pooter'. Those inhabiting bark or rock crevices are readily gathered by this method, as are many of the larger forms in leaf litter. The technique is not adequate for the smaller mites or for those living cryptically in soil, litter, moss, or lichen. These must first be expelled from their habitat by exploiting their aversion to low humidity. The sample is placed on a sieve in a funnel, and an incandescent electric lamp is suspended above it as a source of heat. A collecting vessel containing, for instance, 50% ethyl alcohol is placed beneath the funnel opening to catch, kill, and temporarily preserve the animals as they emerge from their drying environment. Many modifications of this basic pattern of extractor have been devised, to allow for greater efficiency and/or for multiple sample extraction.
Preservation
Cryptostigmatids may be satisfactorily preserved in 70-80% ethanol. It is recommended that up to 5% of glycerol should be added as a safety measure so that the specimens do not dry out. Indeed, several workers have advocated the preservation of cryptostigmatids in pure glycerol or in ethylene glycol. Small glass vials with airtight caps are suitable for curation, and the smaller specimens may be contained in plugged Durham tubes inverted within the vials themselves. The most satisfactory plugs for the Durham tubes, where available, are small portions of botanical pith or dried bracket fungus (Polyporus) taken with a suitable cork borer.
Preparation for study
Cryptostigmatid mites are best studied in temporary preparations. The most suitable mounting and clearing medium is lactic acid used cold or warm and at 50-100% dilution, according to the degree of sclerotisation of the specimen. Individuals should ideally be transferred to a drop of lactic acid in a cavity slide, covered with a coverslip, and placed on a hotplate for gentle warming. Lactophenol is also a good clearing agent, especially for the more heavily sclerotised specimens.
Temporary preparations are not suitable for permanent storage. For this, several slide mounting media are available; the most widely used is de Faure's medium:
| Distilled water | 50 ml |
| Chloral hydrate | 50 g |
| Glycerol | 20 ml |
| Gum arabic or acacia | 30 g |
This medium is water-soluble, and the slide mount may be recovered by soaking in water. For permanent storage the coverslip should be ringed with Glyceel or with nail varnish. Cobb slides, in which the specimen is sandwiched between two coverslips held in an aluminium frame, are the most suitable for permanent mounts because the specimen may be viewed from two sides.