A two step centrifugation method with water and sucrose to separate mites from raw extracts of tullgren funnels

Abstract

Tullgren funnels are commonly used when extracting mites from substrates for ecological and taxonomic studies. During this process, extracted mites are often contaminated with soil particles and other debris, making the processing of those organisms difficult, especially for the smaller mites, such as Tarsonemidae. The Water Sugar-Water (WSW) method, here described here, is intended to facilitate the separation of the extracted mites from those fouling material. It consists of a modification of the Jenkins method, used for the extraction of nematodes. Through a combination of centrifugation with two steps of floatation (first in water and then in 1.5 molar sucrose solution), this method separates mites from contaminants. In this study, the WSW method was tested in different conditions including three soil textures, two storage times (3 days or 6 months) and leaf litter. We also evaluated the possibility to use this method for separation of the broad mite, Polyphagotarsonemus latus (Banks) (Tarsonemidae), given its common occurrence in fields where the present work was conducted. Eight of nine treatments performed consistently well with extraction efficiencies >95% (mites collected in relation to total mites present in the funnel extraction), with no significant differences among them. One treatment, using the addition of kaolin clay to the sample, retained some Phytoseiidae in the sediment pellets, reducing extraction efficiency to 88.3%. Mites of the taxa Acaridae, Cunaxidae, Eupodidae, Laelapidae, Phytoseiidae, Scutararidae, Tarsonemidae, Tydeidae, Rhodacaroidea and Orbatida were successfully removed from contaminated samples with this method. The frequency of these taxa was equally distributed between the water and sugar-water steps of the two-step floatation method. This method is fast, uses inexpensive and non-toxic compounds and has great potential for use to determine the presence of mite groups most commonly found in extractions of Tullgren funnels.