NEMATOLOGY 100
Laboratory Exercise 8
Rev. 10/23/2012

Purpose:  Migratory endoparasitic nematodes:  morphology, anatomy, biology, feeding habits -- Hoplolaimidae, Pratylenchidae (Tylenchina, Tylenchoidea)

     1.   Powerpoint presentation of characteristics.

     2.   Specimens of the following nematodes are provided for study in lab periods 8 and 9:

             a) Helicotylenchus sp. (a spiral nematode) from bermuda and other grasses, UC Davis Quad.
  b) Helicotylenchus sp. (a spiral nematode) from box elder (Acer negundo), Putah Creek.
            c) Pratylenchus penetrans (a root lesion nematode) from Easter lily, Del Norte County, California.
 e) Pratylenchus vulnus (a root lesion nematode) from grape, UC Davis.
            f) Hirschmanniella pomponiensis from cattail (Typha sp.), Yolo County, California.

Hand-pick live adults of the Helicotylenchus sp.,  Pratylenchus sp. and Hirschmanniella sp.  Draw the nematodes, observing the following characteristic features:

           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.

     3.   Key the specimens of three populations of Pratylenchus provided to species using the key to the nine common Pratylenchus species of California.

    4.  Based on general anatomy and morphology, presence or absence of males, etc. would you consider it likely that the two Helicotylenchus examples are the same species of nematode?

    5.  Pratylenchus penetrans and Hirschmanniella pomponiensis are in the same nematode family, Pratylenchidae.  There stylets and esophageal structures are morphologically similar. According to the species the original species descriptions they have the following average morphometric characteristics:

  Pratylenchus penetrans Hirschmanniella pomponiensis
Body length (mm) 0.58 1.9
a (=body length (μm) / body width (μm) 25 66
b (= body length / esophagus length) 6.6 14
Stylet length (μm) 16 20
Males common common

     For the purpose of this exercise, and for class discussion, consider both nematodes to be cylindrical.  What can we infer from these dimensions about resource partitioning, growth rates,  and population increase if rates of feeding are similar? Or if they are not similar?

    6.   Note the taxonomic position of these nematodes in the suborder Tylenchina.

    7.   Examine descriptive charts of the migratory endoparasitic nematodes in the Hoplolaimidae and Pratylenchidae.

     8. Movie

Behavior of Pratylenchus penetrans

     9.  Study photographs of characteristics and damage by migratory endoparasites: Pratylenchus

    10.  Lab Project introduction: 

               Powerpoint presentation: Nematodes as Bioindicators.

     11.   Homework Assignment:

          NEMAPLEX Exercise
          Main Menu:
               Select...Biology and Taxonomy
                Select..Phylogenetic Classification
                 Select...Rhabditida then Tylenchina
               Select...Hoplolaimidae
                           Review Helicotylenchus including some of the species
                            Review Hoplolaimus including some of the species
                           Review Scutellonema including some of the species

               Select...Pratylenchidae
                           Review Pratylenchus including some of the species
            Return to Main Menu
            
     12.   Nemabase Exercise

           Review the host range of these nematodes.  What are the indicated non-hosts?  Are there resistant cultivars available?
          From the Nemaplex main Menu, select Management and Decision Support, then Nemabase 2012.

         Alternatively, you can access the data from the descriptive page for each nematode. 

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NEMATOLOGY 100

Key to the Nine Common Pratylenchus Species in California

1.  Monosexual species, no sperm in spermatheca, males rare or unknown. 2
Bisexual species, sperm in most spermatheca, males common. 7
2. Very large, round stylet knobs, stylet averages 19 Ám in length; V% 82-89; 2 lip annules P. brachyurus
Stylet knobs oval or flattened, stylet generally less than 19 Ám long 3
3. Tail tip annulated, 3 lip annules P. crenatus
Tail tip smooth 4
4 Lip annules 2 5
Lip annules 3 6
5 Average V%=84, lip annules about same width; stylet knobs often flattened; vulval lips somewhat smooth P. neglectus
Average V%=78%, anterior lip annules markedly narrower than posterior; vulval lips protrude somewhat P. scribneri
6 Tail normally truncate, stylet averages 18 Ám in length;  V% averages 76; normally assumes a "J" or "C" shape when heat killed P. zeae
Tail narrowly rounded, stylet averages 16 Ám in length;  V% averages 71; normally almost straight when heat killed P. thornei
7 Lip annules 2, occasionally 3 on one side P. coffeae
Lip annules 3, occasionally 4 on one side 8
8 Spermatheca normally round, posterior uterine branch 1 to 1.5 body widths long; large stylet knobs P. penetrans
Spermatheca normally oval, posterior uterine branch generally greater than 2 body widths long; moderate sized stylet knobs P. vulnus

 

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