Nematology 100                                             Name:

MID-TERM EXAM, 10/31/2012

90 minutes

1. (25 points)

You are provided with a smorgasbord of nematodes extracted from soil around the roots of plants.

 a. Place an adult female plant-parasitic nematode of any species on a microscope slide.  Kill the nematodes with gentle heat.

Apply a coverslip.

Seal the edge of the coverslip with fingernail polish to prevent the slide from drying out.

Place the slide on the compound microscope and adjust the microscope to provide Köhler illumination.

 b. Indicate on your exam sheet the Class and Order of your nematodes.

 c. Draw and label the component parts of the esophagus and reproductive structures for this type of nematode (either from your specimens, or from your knowledge of anatomy and morphology, or both).

 d. Which of the morphological and anatomical characteristics of the specimens suggest that the nematodes feed as ectoparasites?

Which characteristics suggest that they feed as endoparasites? 

 e. Call the instructor for examination of your nematode. If there is more than one nematode present in the microscope field, indicate the specimen you wish to have examined. Do not expect the instructor to make the selection.

Only the nematodes that you indicate initially will be considered.

 Grading:

1. adult female plant-parasite, good condition                    10 pts.
2. adult male plant-parasite, good condition                         4 pts.

or, juvenile or non-parasite, good condition                               3 pts.

3. correct designation of Class and Order                            3 pts.
4. reasonable justification of feeding habit designation        4 pts.
5. correct drawing and identification of esophagus  and reproductive structures                                         8 pts.

6. points off for damage, distortion, dry slides, microscope not in Köhler illumination, etc.

2012 addendum:

If you are unable to hand-pick a nematode within a reasonable period of time (say 5 minutes), don’t panic!  You may concentrate your sample by centrifuging but incur a 5 point penalty.

2.  (15 points)

a.     Label parts of the digestive, nervous and excretory systems depicted in the three nematodes above.

 b.     Indicate the probable feeding habits (and why) of nematode A.

 c.    Indicate the probable feeding habits (and why) of nematode B.

 d.    Indicate the probable feeding habits (and why) of nematode C.

 e.    Indicate the Order for each nematode according to recent classification schemes.

 3.  (10 points)

 a. Describe the life cycle and feeding habits of nematodes in the genus Radopholus.

 b. Briefly describe the damage to banana plants caused by the burrowing nematode, a species of this genus.  Consider damage at the local level in root tissues and at the whole plant level.

 c. What other root-feeding nematodes have similar damage effects in banana plants?

4.  (10 points)

Describe the interactions among organisms that increase the severity of bacterial canker of peach in California.  What organisms are involved?

5. (10 points)

Plant cells apparently recognize parasites and pathogens of plants by surface molecular patterns (PAMPs).  Describe a series of plant defense reactions invoked by recognition of a PAMP signal.

6.  (10 points)

    On the field trip you recovered the dagger nematode from a grape vineyard and the lesion nematode from a walnut orchard.      You also studied the nematodes in the laboratory.

    Provide the following general and diagnostic characters in the table below (answer by using the appropriate letter).

7.    (10 points)

 Describe the feeding process in Paratrichodorus minor (the stubby root nematode).

 8.  (10 points)

 True or False

 a.    NEPO viruses have polyhedral particles and are transmitted to plants by nematodes in the family Trichodoridae.

 b.    Nematode transmitted viruses cause severe plant problems because the virus titer increases enormously due to replication in the nematode.

 c.    Corky ringspot virus in potatoes is transmitted by nematodes.

 d.    The c-p (colonizer-persister) classification scheme for soil nematodes is based on their feeding habits.

 e.    Males of pin nematodes (Paratylenchus spp.) apparently progress through the juvenile stages to adulthood without feeding.

 f.     Plant-feeding nematodes with long stylets are generally ectoparasites.

 g.    Phasmids are chemosensory structures located in the lateral field in the posterior region of many soil nematodes.

 h.    The feeding structure of dorylaimid nematodes is known as a stomatostyle.

 i.      Feeding by dagger nematodes on roots of grapevines causes galling at root tips and damage to root meristematic tissue.

 j.      Longidorus can be distinguished from Xiphinema by the lack of flanges on the odontophore and the anterior location of the guiding ring.

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