Nematology 100 Laboratory Project

Fall Quarter, 2012

Nematode Collections and Soil Nematode Faunal Analysis

    During the quarter you will learn to recognize many different genera and species of plant-parasitic nematodes. While these nematodes are important pests in agroecosystems, there are many other nematodes in the soil that play important functional roles in the biology of soils. These "free-living" nematodes are part of the soil food web and behave as bacterivores, fungivores, omnivores and predators at various trophic levels. Some participate in nutrient cycling and mineralization; others may regulate the abundance of organisms at lower trophic levels.

    Nematode faunae of different ecosystems vary in the presence, abundance and proportion of various taxa. Valuable information regarding soil processes and health and, we think, the status of the soil food web, can be obtained simply by taking a soil sample, identifying and counting the nematodes present, and analyzing the data collected.

Objectives:

1. To improve your understanding and knowledge of nematode extraction methods.
2. To gain experience in identifying plant-parasitic nematodes collected in your soil samples.
3. To expose you to the diversity of nematodes that can be found in every soil sample.
4. To use a nematode faunal analysis to evaluate the biological condition of the soil you collected.

Assignment:

• a)  Each Wednesday, bring a soil sample to class from the UC Davis campus, your home or your travels.
• b)  Indicate the source, location, plant associations and date of collection. GPS coordinates would be ideal.
• c)  During the Wednesday lab period, two students will extract nematodes from their samples by sieving and Baermann Funnel. 
• d) Nematodes will be collected from the extracted samples at the Friday lab.
• e) Part of the Friday lab period will be spent examining nematodes in your collection with the instructor and discussing their characteristics.
• Nematodes from the remainder of the student samples will be extracted by the instructor for demonstration and use in future lab periods.

B. Faunal Analysis Project

1. Collect a soil sample from an area that you find interesting, perhaps your backyard, your home town, from your favorite hiking area or somewhere on the UC Davis campus. If you are sampling a field or a garden, take several 25-30 cm deep random samples from the area (close to the root zone if there are plants) and combine them. Think about whether the sampling sites you choose are representative of the soil you wish to evaluate. You will need about 500 cc of soil to do your soil analysis.
2. You should collect your sample before October 20. Store your sample in a plastic bag in a refrigerator, but do not freeze. Provide about 100 cc of your sample (appropriately labeled) to the instructor. Where possible, plant-feeding nematodes from your sample will be used as examples during the class.
3. Extract the nematodes from the remainder of your sample. You will need to choose the appropriate nematode extraction technique depending on your sample. The instructor can help you decide which technique to use.
4. Examine the nematode community. The instructor will be delighted to help you distinguish between different trophic groups and functional guilds of nematodes.
1. Count the total number of nematodes in your sample. This can be done using a dissecting microscope. Record this number.
2. Use a compound microscope to identify the first 100 nematodes in your sample. Besides identifying the plant-parasites, you will be placing nematodes into their functional guilds (Fig. 1).

Fig. 1. Functional guilds of soil nematodes characterized by feeding habit (trophic group) and by life history characteristics expressed along a colonizer-persister (cp) scale (after Bongers and Bongers 1998). Indicator guilds of soil food web condition (basal, structured, enriched) are designated and weightings of the guilds along the structure and enrichment trajectories are provided.

              c.  Use the Nematode Faunal Analyzer software in Nemaplex to determine the "enrichment status" of  the   soil environment, the degree of "trophic connectance" in the soil food web and the paths of carbon and energy flow through the food web.

Select Nematode Ecology from the Nemaplex Main Menu

  Then Nematode Faunal Analysis

      Then Nematode Faunal Analyzer Spreadsheet.  There you will see how the data you record in the table below are used.

 To see how a more advanced analysis would be conducted, you could view the  Family Level Faunal Analysis for Multiple Samples Spreadsheet.

5. Think about and report to the class the composition of your soil nematode fauna. Based upon the location where the sample was collected would you expect to see a large abundance of bacterial-feeding nematodes? Or maybe fungal-feeding nematodes? What does the composition of your soil nematode community tell you about the "health" of the soil? The instructor or TA will help you to construct a faunal diagram (Fig. 2) as an indicator of the state of the food web in your soil.

Fig. 2. Status of the soil food web, as indicated by nematode faunal analysis, in ten northern California prune orchards.

References

Bongers, T., and M. Bongers, 1998. Functional diversity of nematodes. Appl. Soil Ecol. 10, 239-251.

Ferris, H., T. Bongers, and R. G. M. de Goede.  2001.  A framework for soil food web diagnostics:  extension of the nematode faunal analysis concept.  Applied Soil Ecology 18:13-29.

Nemaplex – Nematode Ecology – Nematode Faunal Analysis

Nematode Faunal Analysis

FunctGld	Functional	c-p	Enter Your	Representative	Basal	Enrich.	Structure
Code	Guild	value	Data Here	Families	Wtg	Wtg	Wtg
b1	Enrichment Indicator Bacterial Feeders - Active Stages	1		Rhabditidae, Diplogastridae, Panagrolaimidae	0	3.2	0
	Dauer Stage of Enrichment Indicators	1		Rhabditidae	0	0	0
b2	Basal Indicator Bacterial Feeders	2		Cephalobidae, Plectidae	0.8	0	0
b3	Bacterivores	3		Prismatolaimidae, Teratocephalidae	0	0	1.8
b4	Bacterivores	4		Amphidelidae, Alaimidae	0	0	3.2
b5	Bacterivores	5		Isolaimiidae	0	0	5
f2	Enrichment and Basal Fungal Feeders	2		Aphelenchidae, Aphelenchoididae	0.8	0.8	0
f3	Fungivores	3		Diphtherophoridae	0	0	1.8
f4	Complex Fungivores	4		Leptonchidae	0	0	3.2
p1	Opportunistic Predators	1		Neodiplogastridae	0	3.2	0
p2	Apehelenchoid Predators	2		Aphelenchoididae	0.8	0	0
p3	Small Specialist Predators	3		Tripylidae	0	0	1.8
p4	Large Specialist Predators	4		Mononchidae	0	0	3.2
p5	Large dorylaimid Predators	5		Discolaimidae	0	0	5
o4	Small Omnivorous Generalist Predators	4		Dorylaimidae, Qudsianematidae	0	0	3.2
o5	Large Omnivorous  Generalist Predators	5		Aporcelaimidae	0	0	5
	Total Nematodes in Sample

 

FunctGld				Herbivore
Code	Plant-feeders:	Number	Representative Types	Wtg.
h2a	Root Associates; root hair/surface feeders		Tylenchidae	0.8
h2	Migratory Ecto/Endoparasites of stems, bulbs, leaves		Anguinidae	0.8
h3	Migratory Ectoparasites: Criconematoidea; cortex feeders		Ring, sheath, pin nematodes	1.8
h3	Migratory Ectoparasites: Tylenchoidea; short-stylets, epidermal feeders		Stunt nematodes	1.8
h3	Migratory Ectoparasites: Tylenchoidea; long stylets, root tip and deep feeders		Sting, awl nematodes	1.8
h4	Migratory Ectoparasites: Triplonchida; curved spear, root tip feeders		Stubby root	3.2
h5	Migratory Ectoparasites: Dorylaimida; long spears, root tip feeders		Dagger, needle	5
h3	Migratory Endoparasites: Tylenchoidea		Lance, spiral, lesion, burrowing	1.8
h3s	Sedentary semiendoparasites: Tylenchida		Citrus, reniform	1.8
h3s	Sedentary endoparasites: Tylenchina		Root knot, cyst	1.8