NEMATOLOGY 100

Laboratory Exercise 12

Rev. 11/04/2008

Purpose:  Above-ground feeding nematodes:  morphology, anatomy, biology, feeding habits -- Aphelenchoides, and Bursaphelenchus (including former Rhadinaphelenchus) (Tylenchida, Aphelenchina, Aphelenchoidea, Aphelenchoididae -- all plant parasites) and in the same family, Seinura (predator), Cryptaphelenchus, Entaphelenchus and Parasitaphelenchus (all insect parasites).  Also, in the family Aphelenchidae, Aphelenchus avenae (fungal feeder).

1. Slide presentation of characteristics.

2.  Examine extractions for specimens of Aphelenchoides fragariae from fern leaves from the Plant Science greenhouses.

     Also examine Laimaphelenchus sp. from the bark of Monterey pine (Pinus radiata) in El Dorado County.

     Draw the nematodes observing the following characteristic features where appropriate:

          a)   stylet length and morphology.
          b)   esophagus, type and anatomy, nature of postcorpus interface with intestine.
          c)   male and female reproductive structures.
          d)   general shape when heat-relaxed.

e)   tail configuration and mucro.

3.   Examine plant material affected by Bursaphelenchus  cocophilus and the palm weevil vector, and pine wood affected with Bursaphelenchus xylophilus and its cerambycid beetle vector.

4.   Note the taxonomic position of these nematodes in the order Tylenchida and suborder Aphelenchina

5.   Examine the descriptive charts of these plant-parasitic nematodes in the Aphelenchoididae

6.   Examine Aphelenchus avenae feeding on Rhizoctonia solani.  Note the range of life stages, observe egg laying and feeding.

7.   Anhydrobiosis experiment.  During the last class you allowed dishes of Aphelenchus avenae  and Hirschmanniella pomponiensis to dry down.  Add water to each dish and observe periodically.  Do the nematodes recover activity?  Does the rate of nematode recovery correlate with your expectations based on feeding habits and life history of the species?

8.  Lab Project:

• Count the nematodes that you extracted from your soil samples.
• Divide the suspension in half, save one half for future lab periods and centrifuge the other half. 
• Siphon off the supernatant and resuspend the pellet in the small volume of water remaining. 
• Place suspension on a microscope slide, immobilize nematodes with gentle heat, apply coverslip and seal. 
• Categorize 100 nematodes into functional guilds per lab handouts and instruction.
• Record data on sheet provided.

 

9.  Study photographs of characteristics and damage by foliar and other nematodes of the Aphelenchina that feed above ground.

10.   Homework Assignment:

        NEMAPLEX Exercise
          Main Menu:
               Select...Biology and Taxonomy
                Select..Phylogenetic Classification
                 Select...Tylenchida
               Select...Aphelenchoididae
                           Review Aphelenchoides, including A. fragariae and A. ritzemabosi.
                           Review Bursaphelenchus, including B. xylophilus and B. cocophilus. 
           Return to Main Menu
           

 11.   NEMABASE Exercise

           Main Menu
            Select Decision Support

                       Select Host Status Database

 

Determine the host range for the genera Aphelenchoides and Bursaphelenchus.

In Nemabase select "All Plants" and "Genus" Aphelenchoides and Bursaphelenchus. 

Also examine the host range of individual species.
Set "Host" filter to Host.  Process.

  

12.  Videotapes:  (as time permits!)

        a)  The Pine Wilt Nematode (Bursaphelenchus).
        b)  Ditylenchus dipsaci responding to a CO₂ gradient.

        c)  Gastromermis rosea parasitizing Chironomus anthracinus (Diptera). (unrelated to nematodes in the Aphelenchina, except that it is an insect parasite).

13.  Review current news items in Nemaplex, and the document on "A History of Nematology in California"

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