Re: [compost_tea] "Micro" nematodes

From: <soilfoodweb_at_aol.com>
Date: Sat, 01 May 2004 13:31:22 -0400
The real reason microscopes are needed to see nematodes is because they are transparent, for the most part.  Without a microscope, and without proper extraction, the nematodes sitting on organic matter will not be seen.  They blend in.

So, what extraction method are you using to pull the nematodes out of the material? 

Most nematodes can, barely, be resolved by the naked eye.  But nematodes are a great deal easier to find with the help of a microscope.  So, there is a slight controversy in the scientific world about whether nematodes are truly "microoganisms", or not. 

One definition of microorganism is that it requires a microscope to see microorganisms.  Nematodes would then sit right on the fence with respect to that definition.  You can see them without a microscope, but you sure can't ID them without a microscope.  That last point is what usually clinches any argument with a microbiologist.  You can't tell who the critter is if you don't use a microscope, so nematodes are microorganisms.

But, no such thing as micro-nematodes.  Let's not confuse the lay public, or even the academic world, by inventing new terms.  We have enough inapproriate terminology and jargon as it is.  Let's not invent more. 

Nematodes come in four functional groups -
1.  Bacterial-feeding nematodes
2.  Fungal-feeding nematodes
3.  Predatory nematodes
4.  Plant-feeding nematodes, which includes the root-feeding and foliar-feeding nematodes

People separate out a fifth group, "switchers", or nematodes that have the equipment to feed on roots, or feed on fungi.  I've seen the same species chewing on roots, and chewing on fungi, so I take the attitude that they are capable of doing both.  How much to these nematodes actually switch, in the field?  Well, if they are strictly root-feeders, I've seen these organisms living happily in soil that has no plant in it, just fungi.  I've seen them happy as campers living in soil with no fungi, but lots of roots.  The plants aren't happy either.  So, strong suspicion that they can indeed eat fung iand roots, as they need to.  But - no published papers showing the switch, so the final chapter is yet to be documented. 

There are small size bacterial-feeders, but most of the bacterial-feeders are large size.  Some bacterial-feeding nematodes consume pathogenic bacteria, and some bacterial-feeding nematodes eat good-guy bacteria.  No clear grouping of bad-bacteria feeders or good bacteria feeders.  So, most likely, the bacterial-feeders just eat whatever they can put in their mouths, without regard to what is good, bad or indifferent for the plants. 

But it means distinction of "big" versus "small" nematodes as being "good" or "bad" is a bit iffy.  Still, it might be a generally useful distinction.  The little nematodes are in general root-feeders or foliar-feeders, while the bigger ones, are in general the more beneficial species. 

But not a perfect fit, and they ALL require a microscope to be identified. 
--
Elaine Ingham
President, Soil Foodweb Inc.
SFI Corvallis, OR
SFI Port Jefferson, NY
SFI Lismore, NSW, Australia
SFI Hilversum, The Netherlands
SFI Cambridge, New Zealand
SFI Culiacan, Mexico
SFI Jerome, Idaho
http://www.soilfoodweb.com


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Received on Sat May 01 2004 - 15:25:45 EDT

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