A versatile nematode water bath apparatus.

T h e activity of nematodes in unstirred water frequently decreases due to the depletion of oxygen from their surrounding microenvironment (1,2,3,). In in vitro studies on the activity of Nothanguina phyllobia T h o r n e we found it essential to prevent this by constantly agitating nematode suspensions. Various physiological processes are undoubtedly affected at oxygen tensions which inhibit activity, and the need for agitation arises in studies of nematode survival, lipid utilization, and toxicology. Nematode activity and metabolism are also sensitive to temperature; the rate of movement of N. phyllobia juveniles, for example, increases 25% over the range 19-24 C (Robinson, unpublished data). T o solve these problems, we designed and buil t a spaceefficient, mult itemperature water bath apparatus specially adapted for nematodes. It provides shaker capability as well as precise microscope stage temperature control (-+ 0.2 C) (Fig. 1). It is constructed from readily obtained parts and requires < 10 A (115 V) under full load. T h e basic design may be modified to provide any number of temperatures simultaneously. With our part icular arrangement, we are able on a 1-m length of laboratory bench to store, shake, and microscopically observe twenty 25-ml samples at five temperatures in tile range 0-60 C (I00 total samples). T h e apparatus consists of four assemblies (Fig. 2), each of which can be buil t and installed separately: a water bath assembly (B), an electrical power/water pressure manifold (M), an observation well assembly (W), and five water bath reservoirs (RES). T h e machine requires external pressurized hot and cold water sources. We use an icecooled Styrofoam (polystyrene) container with a 0.03 kW outpu t magnetic drive pump for cold water and a commercially manu-