NEMATOLOGY 100

Laboratory Exercise 6

Rev. 01/01/2020

Purpose:  Ectoparasitic nematodes of the Criconematoidea. 

          Morphology, anatomy, feeding habits:
          Criconematidae: Criconematinae and Hemicycliophorinae;
          Tylenchulidae: Paratylenchinae. 

     1.   Powerpoint presentation and slides of characteristics.

     2.   Hand-pick, from the specimens provided, live adult males and females of:

                    a) Mesocriconema xenoplax

                    b) Paratylenchus sp.

                    c) Hemicycliophora sp.

                   
 Note the diversity of nematodes in the samples. 

 Sources: M. xenoplax was obtained from the field trip salnut orchard in Winters, CA; Paratylenchus from from grape cv Colombard, Davis,  Hemicycliophora from sedges in a stream in Mix Canyon, near Winters, CA.

          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.

      There are questions regarding identification of the nematodes indicated as Criconemoides.  The genus (sensu lato) has undergone several redescriptions over the last 20 years.  Use the key to the Criconematidae provided in Nemaplex.

             a) are these nematodes correctly described as Criconemoides, or are they Mesocriconema?

             b) is the genus xenoplax?

     4.   Note the taxonomic position of these nematodes in the Criconematoidea.

     5.   Examine descriptive charts of these and other plant-parasitic nematodes in the Criconematoidea.

     6.   Determine numbers of surviving nematodes from the plant residues experiment set up in lab #4.  Calculate mortality rates in the amended (A) relative to the unamended (U) control treatments.   The calculation is 100(U-A)/U.  Please be prepared to report your result and conclusion in class on Friday.  What are the flaws in the experimental design? Would you design the experiment differently? 

     7.  Complete field trip sampling exercise:

     a) Reliability of population estimates.

• Count the total number of nematodes in the 15-core samples taken from the alfalfa field.
• Identify and count three predominant species of plant-parasitic nematode in the samples (the root lesion nematode, Pratylenchus sp., the stunt nematode, Tylenchorhynchus sp., and root associates of the family Tylenchidae).  There are two possible approaches:
•      a) if you feel cofident in your ability to identify the target nematodes under the dissecting microscope, count the total number of nematodes in the dish and identify the first 50 you see as Pratylenchus, Tylenchorhynchus, Tylenchidae, or Other (or you can identify the Other group according to probable feeding habit if you wish).  Then calculate the total of each group in the sample based on the proportions in the 50 you identified.
•      b) count the total in the sample then centrifuge the sample, concentrate then nematodes in a pellet, spread on a slide, and identify the firsat 50 nematodes you encounter as above.  Calculate the total of each group in the sample.
• Determine the reliability of a single composite sample from the field on the basis of the range and variance of the individual sample estimates.

     8. Movie: the sheath nematode, Hemicycliophora arenaria.

     9.  Study photographs of characteristics and damage by migratory ectoparasites: Criconemoides, Hemicycliophora and Paratylenchus.

    10.   Homework Assignment:

          NEMAPLEX Exercise
          Main Menu:
              Select...Biology and Taxonomy
                Select..Phylogenetic Classification
                 Select...Rhabditida

                   Under Tylenchina select...Criconematidae
            Review Criconemoides, including M. xenoplax,   
                        Hemicriconemoides chitwoodi and Hemicycliophora arenaria.
               Select...Tylenchulidae
                           Review Paratylenchus, including P. hamatus, 
                           P. neoamblycephalus and P. projectus. 
           Return to Main Menu
            
       11.   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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