3. Release the nematodes in a water drop exactly at mid-point in
the center pot.
4. Allow for good passive diffusion of the attractants from the
surrounding pots to the central arena.
5. Disassemble the olfactometer after 1 day of the nematode
release.
6. Place the sand in individual removable glass tube on a distinct
19-cm diameter cotton filter disk.
7. Place the disk containing sand inside a Bearmann extractor.
8. Count the number of nematodes in the collection tube using
dissection microscope.
9. Use these numbers as a measurement of the attractiveness of
each tested odorant (Fig. 1).
5 Chemotaxis Assay
EPNs respond differently to different host odors. Some odorants
are appealing and revolting, and some have no specific response.
The entomopathogenic Steinernema can jump, that is supposed to
have a vital function in host-seeking and dispersal [149]. Jumping
and chemotaxis assays are efficaciously applied to identify odorants
which kindle these behaviors in a number of nematodes [150].
Fig. 1 Six-arm olfactometer to test nematode attraction
Chemotaxis Assay
39