A Procedure for Extracting Large Numbers of Debris-Free, Living Nematodes from Muddy Marine Sediments

Abstract

Procedures commonly used for extracting nematodes from sediments do not provide sufficient quantities of living, chemically unaltered individuals required for biochemical studies. Microscopic hand-sorting and centrifugal flotation techniques either are too time-consuming or may be physically and/or chemically damaging to the organisms. A simple, time-efficient extraction procedure which modifies the Baermann funnel apparatus with a filtering layer of glass beads or sterile dune sand is described. With only three hours of technician time for set-up and harvesting, six funnels provided a combined yield of 35,000 living nematodes free of sediment and debris. The experimental study of meiofauna using biochemical techniques, such as dietary immunoassay (Feller et al., 1979) or stable isotope tracers (Peterson et al., 1986), has been hindered by the time-consuming effort required to obtain needed quantities of meiofaunal organisms. For example, to measure carbonstable and nitrogen-stable isotope composition of nematodes, assuming an individual dry weight of 2.5 ,ug (Sikora et al., 1977), about 8,000 debris-free nematodes (20 mg dry weight) are required. At least 500 mg dry weight of nematodes is required to prepare antisera for immunoassay studies. However, adequate quantities of clean, debris-free nematodes are necessary if such biochemical techniques are to be feasible. No published account of a single procedure exists which describes rapid extraction of large quantities of living, chemically unaltered nematodes that are free of sediment or detrital particles. Microscopic hand-sorting, as recommended by Hulings & Gray (1971), requires at least 15 h to obtain 8,000 debris-free nematodes. Centrifugal flotation techniques using sucrose (Heip et al., 1974), or colloidal silica (de Jonge & Bouwman, 1977; Nichols, 1979; Schwinghamer, 1981) are not applicable where living, chemically unaltered meiofaunal organisms are required. Colloidal silica is toxic; sucrose may be absorbed or assimilated by the organisms. A simple extraction procedure was devised, based on a modification of the Baermann funnel (Oostenbrink, 1960), in which glass beads or sterile dune sand are used as a filtering layer. Extraction relies on downward migration of nematodes from concentrated natural sediments, through glass beads or sterile sand, into clean, filtered seawater. Contribution Number 685 from the Belle W. Baruch Institute for Marine Biology and Coastal Research. This work was supported by NSF Grant OCE85-21345 to B. C. Coull and R. J. Feller. 2 Present address: Institute of Ecology, University of Georgia, Athens, Georgia 30602, U.S.A. TRANS. AM. MICROSC. SOC., 107(1): 96-100. 1988. ? Copyright, 1988, by the American Microscopical Society, Inc. This content downloaded from 157.55.39.112 on Wed, 29 Jun 2016 04:56:14 UTC All use subject to http://about.jstor.org/terms VOL. 107, NO. 1, JANUARY 1988